[HN Gopher] Solar panels + cold = A potential problem
___________________________________________________________________
Solar panels + cold = A potential problem
Author : behnamoh
Score : 159 points
Date : 2025-09-28 01:48 UTC (21 hours ago)
(HTM) web link (www.linspyre.com)
(TXT) w3m dump (www.linspyre.com)
| BobbyTables2 wrote:
| Why would lower temperatures lower the maximum voltage?
|
| Sure, diode forward voltages change a little but seems like
| something else is going on...
| AgentK20 wrote:
| It's not that it lowers the maximum voltage that the charge
| controller/inverter can handle. It's actually that the panels
| become MORE efficient in the cold temperatures, resulting in a
| (potentially unconsidered by end-user) increase in voltage,
| overwhelming the downstream BoS components.
| mindslight wrote:
| Solar panel voltage goes up as temperature decreases. The chart
| is misleading, it's stating something like an equivalent max
| voltage if you think of the solar cell voltage as staying the
| same (and presuming your temperature coefficient matches)
| bobjordan wrote:
| Lower temperatures increase PV max voltage output, not lower
| it. Conversely, when solar panel temperature increases, voltage
| decreases. So the headline specs/outputs assume to be valid at
| a particular temperature. As the temperature of the panels
| change, the realized performance changes.
| objectcode wrote:
| I think it works this way but I could be wrong: 1. The forward
| voltage across a diode depends on the current, and the graph is
| r-shaped. For a certain diode, 0.01A might make the voltage
| across it 0.4V, 0.1A might be 0.6V, 1A might be 0.65V. 2. The
| forward voltage also depends on the temperature of the diode.
| For a certain diode, per degC decrease there could be a 0.002V
| increase.
|
| Let's say with certain current there is 0.687V. If two diodes
| are connected in series i.e. (point a) - diode 1 - diode 2 -
| (point b), and each has a 0.687V voltage across, that's 0.687 +
| 0.687 = 1.374 V between point b and point a.
|
| For the solar diodes, the "current" depends on how "strong" the
| sun is. If at a certain "current", across each diode is 0.687V,
| you'll need 216 diodes in series (between two points) to get
| 0.687x216[?]148.4 V.
|
| If there is 0.002 V increase per diode per 1degC decrease, with
| 216 diodes, that's a 0.002x216=0.432V increase per degC
| decrease, so with a 4degC decrease it exceeds the MPPT's limit.
|
| Another thing about solar that differs from how diodes are
| "normally" used in circuits is that the "true" voltage depends
| on the max current achievable with the how bright the sun is
| right now, instead of the "true" current. When the "true"
| current is 0 A, the voltage across each diode might be 0.687 V.
| When the "true" current is 0.5 A, maybe 0.65 V. 1A, maybe 0.6V.
| 2A, maybe 0.3V. Try to get more "true" current, the "true"
| voltage drops. Try to get more "true" voltage, the "true"
| current drops. Power is voltage x current so when full speed
| charging, the MPPT uses an algorithm to find the (possibly)
| best minimum (not maximum) input voltage based on the
| temperature etc and trades voltage for current at the output.
| If there is no minimum input voltage restriction, solar will
| follow the battery's terminal voltage + cable drop instead, and
| instead of something like 111V, there could for example be a
| ~4x less powerful 25.5V (if the battery is a "24 V") with just
| 10% more current.
|
| At the MPPTed min input voltage for full speed charging, maybe
| 111V, all might seem well even with low temperatures, but when
| the battery is full and there is approximately nothing using
| electricity from solar, the real input current will be ~0 A, so
| there will no voltage "sag", so the solar will realize the full
| voltage corresponding to the temperature and the illumination,
| potentially >150 V...
| namibj wrote:
| It's not that little given these diodes run between sun baked
| summer and cold soaked winter dawn.
| mindslight wrote:
| Why does the Delta Pro not have a fuse on the input, with the
| MPPT limiting the max voltage to 150v (by upping the current
| until the voltage sags and/or the fuse blows, or even a straight
| crowbar circuit). This is a premium consumer brand selling a
| mostly complete product, and protecting the input from
| overvoltage would be straightforward. The frustration at the
| warranty weaseling isn't surprising.
| avidiax wrote:
| You might think that the voltage rise could be too fast for
| most protective technologies to save the downstream
| electronics, but the general case is that the temperature
| slowly drops and the sun slowly rises. So the voltage should
| slowly approach the limit.
|
| Adding a normally-open relay and a voltmeter and a
| microcontroller should fix this. Relay won't close on startup
| unless the voltage is safe. Microcontroller will open the relay
| if the voltage gradually nears the limit. Should be solvable
| for <$5 in parts.
|
| Dark start (when the batteries are flat w/o grid power) will be
| challenging. There will need to be a small battery to power the
| voltmeter and relay, or a high-voltage tolerant supply to power
| the microcontroller and relay temporarily. A 9V should likely
| be sufficient.
| mindslight wrote:
| Common relays don't handle 150VDC, and I'd spec the voltage
| even higher even though one would think the voltage rating
| has more to do with arc interruption rather than creepage
| while off. Also a microcontroller is complete overkill, draws
| too much current to be easily powerable by the solar panel
| side, and adds complexity for something to go wrong. A simple
| analog comparator suffices.
|
| The standard answer for overvoltage protection is a crowbar
| circuit + fuse, and I think that's what I'd aim for rather
| than a relay. The problem with DIYing that is knowing the
| input capacitance of the Delta and finding out whether it has
| any other problems with its input being abruptly shorted.
| namibj wrote:
| No the DC/DC converter could just turn it's transistors to
| short out the panels and rely on the fuse you want anyways to
| handle idiots paralleling more panels than allowed.
| therein wrote:
| I am sure many are familiar but I found it amusing when someone
| explained to me why it is called magic smoke.
|
| It is because electronics work through magic so when you let the
| magic smoke out, they stop working.
| setterle wrote:
| It's the soul leaving the IC.
| dgfitz wrote:
| I've never heard it called magic smoke before, but a regular
| saying at one of my old jobs was "ah yeah we let the smoke out"
| in relation to 100% electric drive vehicles. Smoked many
| inverters, shorted 96v bus to a 24v bus, etc.
|
| It was almost a rite of passage to "let the smoke out" in that
| org. That job was actually great because as a software engineer
| I happily spent a lot of time with a fluke, a wrench, arm
| buried in the bowels of a vehicle fishing out sockets, etc.
| Writing the software was not the hardest part of those
| programs, but being one of the handful of folks that knew the
| entire electrical, cooling, mechanical, and software systems
| made us the most valuable folks on the program. We had to know
| all those things in order to write the software correctly.
| ggm wrote:
| In the early 80s we used to say electronics ran on magic
| pixie dust, and when you let the pixie dust out as smoke, the
| magic went away.
| ramses0 wrote:
| Hackers dictionary: http://www.catb.org/jargon/html/M/magic-
| smoke.html
| jonathanlydall wrote:
| The presentation helps a lot too, the way I was told it was
| something like:
|
| "Did you know that computers actually run on magic smoke? Once
| the magic smoke comes out though, it stops working."
| hdgvhicv wrote:
| Devices run on magic smoke. When something bad happens the
| smoke escapes and thus the device no longer works.
|
| This is proven by observation - the only thing you see charge
| is the smoke escaping.
| franciscop wrote:
| I was going to comment on the manufacturer's safety margins, but
| then I found a graph [1] on the variability of voltage vs
| temperature and it seems to be a lot steeper than I
| thought/expected, to the point that I'm wondering how these do
| not require either training or a voltage regulator to install and
| operate properly:
|
| https://www.researchgate.net/figure/Module-voltage-current-v...
| fake-name wrote:
| They do!
|
| Basically anything that consumes solar power incorporates
| what's called a "MPPT", or maximum power point tracker.
|
| Basically, it's a smart DC-DC converter that continually tracks
| the voltage/current output of a solar panel and adjusts the
| load to extract the maximum available power from the panel.
|
| It's not uncommon to have issues with extremely high panel
| voltages in snowy climates, when they're first illuminated in
| the morning. If you are close to the maximum voltage your MPPT
| charger can handle in normal circumstances, extreme cold can
| even damage things during the initial morning transient. You
| then have to do oddball things like use a crowbar system to
| prevent blowing up your MPPT system.
|
| (see https://en.wikipedia.org/wiki/Maximum_power_point_tracking
| )
| childintime wrote:
| Note it would be sufficient to shut down (short-circuit) a
| single panel, which is safe, to lower the overall voltage.
| syntaxing wrote:
| Another post commented but that's exactly the point of the
| MPPT. Not only is it temperature dependent but solar incidence
| angle matters too (how the sun angle is relative to the
| surface). MPPT works by changing the internal impedance to
| match the ideal charging voltage. But there's a limit to how
| much it can regulate but I think it's very fair that a consumer
| would expect nominal voltage times panels in series is less
| than the marketed solar input to work.
| namibj wrote:
| There's a reason people don't install electric equipment
| without training.
|
| This is just like not upsizing wire gauge if you have a bunch
| that are loaded simultaneously buried together in a somewhat
| insulating wall. Without the burying under plaster,
| everything would be fine. But combine that with simultaneous
| loading during summer, and you fry/roast the PVC insulation.
| syntaxing wrote:
| > There's a reason people don't install electric equipment
| without training.
|
| I'm not sure if I follow that logic and if your analogy
| follows. I would argue this is closer plugging in an
| appliance rather than running wires. If I run a 15A
| appliance on a 10A breaker, a normal person without
| training would expect the breaker to trip. This is like
| running a 10A appliance and the 15A breaker trips because
| the appliance is sometimes 16A when it works in the cold.
| shepherdjerred wrote:
| > If I run a 15A appliance on a 10A breaker, a normal
| person without training would expect the breaker to trip.
|
| Would the breaker trip in this case? I thought in this
| case it'd be more likely to start a fire.
|
| Edit: thinking about this more, I think I'm wrong. A fire
| would start if your wires were too thin for a given
| amperage. Breakers detect current flowing.
| marcosdumay wrote:
| The part that they are warning about burning out is a voltage
| regulator.
|
| Those things are normally built to handle a nominal 115 V
| assembly of panels. There's probably something on the manual
| about this, but when you put a giant label saying your device
| supports 150V, people are not going to read the manual.
| Animats wrote:
| Why doesn't this just produce a shutdown? Inverters have to track
| voltage and current on the input and outputs sides, and can turn
| themselves off. They shouldn't be that close to the absolute
| maximum voltage ratings on the components.
|
| Too much current is a heat dissipation problem, and you've got
| some time to deal with that, at least tens of milliseconds.
|
| Anyone have a teardown on these things? Are they using under-
| rated MOSFETs? That's all too common in solid state relays from
| China.
| quailfarmer wrote:
| High voltage, low RDSON FETs are (slightly) more expensive, and
| these products are cheap. A better design would use a higher-
| voltage rated input switch with poor (slow) switching
| performance, like an IGBT. Don't design critical infrastructure
| around EcoFlow hardware.
| Animats wrote:
| Fujitsu, which sells MOSFETs for this application, writes:
| "Firstly devices should be rated at 600V or 650V, as this
| will generally provide more than adequate protection against
| the threat of high voltage transients."[1] That's a nice big
| safety margin. It should hold until the voltage monitoring
| shuts the whole thing off.
|
| Not seeing UL certification on this thing.
|
| If we're going to have US protectionism against China, a good
| first step would be to require UL-type testing, carried out
| in the US, on all imported electrical devices that run on
| more than 12VDC or contain a battery chemistry capable of
| thermal runaway. Electrical safety is a solved problem if you
| can keep people from cheating.
|
| [1] https://toshiba.semicon-
| storage.com/eu/semiconductor/design-...
| adrian_b wrote:
| The voltage ratings of the MOSFETs used for 220/230/240 V
| applications have been increased over the years.
|
| Decades ago, when bipolar transistors were used, they were
| rated for 350 V, which is barely enough for 220 V + 10%.
|
| When everybody started to design universal converters
| usable for 220/230/240 V, the ratings were increased to 400
| V. The first power MOSFETs were also rated thus.
|
| Then there were too many converters destroyed by random
| voltage spikes, so the standard ratings were increased to
| 500 V. That proved to still be not enough in many places
| over the world, so the ratings were increased to 600 V or
| 650 V, already many years ago, in order to make extremely
| unlikely the destruction of the transistors by voltage
| spikes much greater than the nominal mains voltage.
|
| 600 V or 650 V is used for converter topologies where the
| transistors see only the peak input voltage. For converter
| topologies that use fewer transistors, but those see peak-
| to-peak voltages, the rating of the transistors must be
| 1200 V.
|
| For 650 V, gallium nitride FETs are the best available
| devices, while for 1200 V or higher voltages silicon
| carbide transistors are the best. Silicon transistors are
| the best only for ratings much lower than 100 V, but they
| may be preferred also at high voltages for being much
| cheaper.
| _fizz_buzz_ wrote:
| My understanding is that mosfets themselves are usually not
| UL certified/listed. I recently did a UL certification of a
| power supply and the IGBTs we used were themselves also not
| UL certified. The UL certification was more about the
| overall system design.
| Aurornis wrote:
| > They shouldn't be that close to the absolute maximum voltage
| ratings on the components.
|
| This appears to be a situation where the engineering team
| determined the absolute maximum input voltage and the
| marketing/product people put that number straight into the
| documentation.
|
| Standard practice with electronic parts is to determine the
| absolute maximum rating, then to specify a recommended maximum
| that allows for some safety margin and variation.
|
| Instead, this company determined the absolute maximum and then
| just shipped it.
| jama211 wrote:
| One way or another, many of us are in agreement the company
| screwed up and it's on them to fix it - whether that's their
| marketing, their manual, their lack of over voltage
| protection, whatever it is it's their fault.
|
| Yet so many people in this thread are so keen to blame the
| customer, it's pure ego from them. "I'm too smart for that to
| happen, so it's all their fault!" they sneer. Classic bad
| faith forum behaviour...
| privatelypublic wrote:
| That's humanity in general. But yea- general guide says
| "add up your open circuit voltage and don't exceed that."
| If something fails because of the panel manages to get more
| than 1000W of solar flux, and is cold... it's the mfgr's
| problem.
|
| I need to actually look up why the extra flux increases
| voltage. Maybe it really doesn't but just moves the MPP to
| a higher voltage by having more current.
| dhosek wrote:
| When I got solar panels for my (former) house 15 years ago, as I
| recall, the best practice was to have panels in parallel (each
| with its own microinverter) and not in serial as serial would
| cause loss of efficiency when there was partial blockage of
| panels. (I could be misremembering all of this).
| NooneAtAll3 wrote:
| you might be misremembering bypass diodes?
| ianlevesque wrote:
| No, microinverters are still a thing (Enphase is a popular
| brand) and they do then get connected in parallel.
| baq wrote:
| There are also power optimizers which are DC-DC and connected
| in series.
| namibj wrote:
| That's only relevant if you're so starved for panel area that
| you can't put them into places that have each sub array
| sufficiently homogeneous and only partially shaded during
| sunrise/sunset.
| syntaxing wrote:
| > Plugging in four 400w solar panels in series is similar to
| filling your gasoline powered car with diesel and wondering why
| the car manufacturer isn't replacing your new car.
|
| I don't think this analogy works. The solar input works like
| Diesel or Gasoline in different temperature. It's pretty
| unreasonable to assume the consumer knows when depending on
| temperature unless the explicitly state in the manual (I'm
| willing to bet good money majority of the people in US have never
| read their car manual either)
| saghm wrote:
| Agreed. No one needs to change which type of gas they use
| because it happens to be a warm sunny day.
| dotancohen wrote:
| In the Corvette community, using a higher octane fuel on
| hotter days is well known to prevent ping.
| jfengel wrote:
| I'm surprised the Vette doesn't call for high octane all
| the time. It's common for high compression engines.
| dotancohen wrote:
| The knock sensor on LT1 and later engines allows one to
| get away with lower octane fuel for day to day driving.
| myself248 wrote:
| Straight Vegetable Oil (SVO) diesel conversions do. It'll gel
| at low temperatures, so they blend or switch to a separate
| tank of regular (or bio) diesel while the engine is cold,
| wait until it generates enough heat, circulate that heat
| along the SVO lines and into the tank, then switch over. Then
| switch back a few minutes before shutdown so the lines are
| full of regular diesel for the next cold start.
| rcxdude wrote:
| Because they run their engines well within the margins of
| their design. If you were running at the edge of the envelope
| you would find that the temperature does matter.
| happosai wrote:
| True for gas not for diesel. You have to switch to winter- or
| arctic diesel if the temperature goes below -20c.
| bryanlarsen wrote:
| Gasoline is also blended differently for summer or winter.
| It's not as crucial as for diesel, but it does make a
| significant difference.
| throw-qqqqq wrote:
| Yeah car analogies suck.
|
| Diesel is blended differently for winter and summer in many
| countries. See this for instance
| https://www.crownoil.co.uk/guides/winter-blend-vs-summer-
| ble...
|
| Around the skiing season, many automotive magazines will
| remind diesel drivers to buy "winter diesel" or use additives
| if e.g. driving up to the Alps or similar cold places.
|
| It's not so black and white :)
| Jgrubb wrote:
| I love a good analogy. This is not a good analogy.
| jfengel wrote:
| I'm not sure I know what a good analogy looks like. If the
| two things are identical, then the analogy is uninformative.
| If they're at all different, you will zero in on the
| differences rather than the similarities.
|
| Sometimes they can be ok pedagogical tools, but they're
| easily misused as tools of persuasion.
| jama211 wrote:
| You're not supposed to zero in on the ways in which an
| analogy doesn't apply. You're simply supposed to read the
| analogy in order to see what it's attempting to _highlight_
| about the scenario.
|
| This is a common pet peeve of mine, people not
| understanding how analogies are supposed to work and
| getting distracted by the differences. They're supposed to
| work like a light filter placed over a lens, something will
| be highlighted and focus on that, don't focus on the fact
| that "but all the colours are different now!", the only
| purpose of using the light filter was to highlight a
| specific part of the image, the fact that it also coloured
| everything wrong temporarily is supposed to be ignored.
|
| You know, just to use an analogy to explain analogies.
| Gotta be as meta as possible.
| nenenejej wrote:
| Why isn't there code/regulations for tbis. Why do you need blog
| advice.
|
| It is like using too thin wiring to your oven or something.
| Because you based it off how you typically use the oven not is
| max draw plus decent margin.
|
| Which is why you get a qualified electrician who knows or get
| qualified yourself.
| unglaublich wrote:
| Okay, but the oven tells you: use at least 8mm^2 wire, and then
| it goes up in flames because hey sometime you actually need
| 10mm^2...
| maccard wrote:
| > Why isn't there code/regulations for tbis. Why do you need
| blog advice.
|
| On pretty much every other device (domestic for sure, I don't
| actually know abount commercial) there is.
|
| > It is like using too thin wiring to your oven or something.
| Because you based it off how you typically use the oven not is
| max draw plus decent margin.
|
| Sure, but with all other electrical labelling the numbers are
| correct. Imagine if Neff said "you only need an 13A rated
| socket" for their oven, and then when you want to bake bread it
| draws more. That's very different to Neff saying "you need
| 45A", and deciding to install it on a 13A socket yourself
| because you don't need to make bread. The former is what's
| happening in this case.
| Aurornis wrote:
| Most household solar systems do require permitting and
| inspections before you can turn it on. There are some
| exceptions in a few states for very small systems now. Ecoflow
| provides equipment for these small legal unpermitted installs.
|
| More importantly, equipment shouldn't self destruct in a
| dangerous fashion when pushed over the limit.
| sbierwagen wrote:
| I am surprised that open circuit voltage is specified at 25degC
| and increases dramatically as the temperature goes down. Seems
| backwards! I'm looking at the Ecoflow spec sheet right now and
| fair enough, it's got the open circuit voltage and then the
| Temperature Coefficient of Open Circuit Voltage (-0.35%/degC)
| right next to it.
|
| Great, guys, how about you go ahead and multiply those two
| numbers _for_ me, since you 're the ones writing the fucking spec
| sheet? It's like if car battery manufacturers only specified a
| cranking amps number, and told you to figure out cold cranking
| amps yourself.
| teiferer wrote:
| > Great, guys, how about you go ahead and multiply those two
| numbers for me, since you're the ones writing the fucking spec
| sheet?
|
| No time. Busy writing blog posts blaming customers.
| BertoldVdb wrote:
| A solar panel is like a normal silicon diode. The voltage over
| the cell goes up drastically with lower temperatures. In cold
| climates crowbars are usually added.
| crote wrote:
| > how about you go ahead and multiply those two numbers for me
|
| What are you going to fill in for the _third_ number, though?
| With an open-circuit voltage of 37.10V at 25degC and a
| coefficient of -0.35% /degC it can _theoretically_ go up to 75V
| at absolute zero. And that open-circuit voltage is with an
| irradiance of 1000 W /m2, should we also account for the
| possibility of someone building a heliostat around it?
|
| There's no one-size-fits-all number they could _possibly_
| quote. It 'll always depend on the environment, because that's
| just how the physics work. The best you can do is provide a
| figure for the standardized testing environment and the
| relevant coefficients - which is _exactly_ what they are doing.
| teiferer wrote:
| Maybe they should just improve their product to make it more
| resiliant, rather than blaming customers for thinking that 148 V
| is below 150 V? Not everybody buying these has a Ph.D. in physics
| and if it says 148 V on the label and 150 V on the other label
| then it's your product that has a problem, not the customer.
|
| And no matter what happens, customer support should help the
| customer, not blame them.
| leoedin wrote:
| In both examples given you can have 2 panels in series.
|
| So given that in almost all use cases, you can have 2 panels in
| series, they should just say "max 2 panels in series". Simple.
|
| A good product hides complexity from the user with sane
| defaults and optional advanced configuration. This feels like
| the same problem.
| cornholio wrote:
| Panels are not standardized and are themselves series-
| parallel constructions with wildly diverse specs.
| TeMPOraL wrote:
| There's hiding complexity, and then there's creating fake
| reality for people.
|
| As it is, panels are gonna produce variable power depending
| on the weather. Putting interoperability with third-party
| panels aside, to get the simplicity of "max 2 panels in
| series", they'd have to either cap the max power on the
| panel/generator link and dump the excess, or set the limit
| based on the worst case a customer is likely to encounter.
| I.e. they're either gonna waste power, or gouge their
| customers for extra hardware. Neither of that makes sense for
| an ecological product sold to a price-conscious customer base
| :).
| namibj wrote:
| The problem is that you run higher voltages with the same
| hardware if your in Alaska than if you're in Florida.
| Substantially so.
|
| "Wasting" those 5~10% during severe winter conditions isn't
| worth splurging on the voltage converter.
|
| Though then selling units that suggest to not run a few
| hundred volt strings before paralleling instead does sound
| bad, as the string doesn't need separate fuses rated to
| many volts DC.
| geocar wrote:
| > Not everybody buying these has a Ph.D. in physics and if it
| says 148 V on the label and 150 V on the other label then it's
| your product that has a problem, not the customer.
|
| Idk. I don't have a PHD, but 220V sounds like 240V to me. I
| wouldn't do this.
|
| I feel like getting advice about how to wire up electronics
| should not be so hard.
|
| > Maybe they should just improve their product to make it more
| resiliant
|
| Adding "resilience" usually adds to the per-unit cost. I think
| making a web page adds some cost too, but at least that can be
| amortised.
|
| > And no matter what happens, customer support should help the
| customer, not blame them.
|
| I think that's happening here: Making a web page to educate
| future customers seems like a really good idea. I wouldn't have
| thought that necessary until I saw it, but I'm always excited
| to learn something new.
|
| The existing customers who did dumb should consider this a
| relatively cheap education in electronics; cheaper than a PHD
| at least!
|
| Also, whether the company also gave them rebates or credits we
| don't know here, but telling "customer support" they "should
| help the customer" is also telling them they're not helping the
| customer, and _you don 't know that_.
| delusional wrote:
| > Making a web page to educate future customers seems like a
| really good idea
|
| I don't think this is an official website of ecoflow.
|
| Other than that I agree. I don't think asking for a bit of
| knowledge from the customers is a bad thing. A warning in the
| manual about safety factors should be enough.
| xenadu02 wrote:
| They're just being cheap. If you're going to let customers
| plug panels directly into your box you should have
| overvoltage protection. It's that simple.
| cornholio wrote:
| > Adding "resilience" usually adds to the per-unit cost.
|
| In this case, the cost is much less than a dollar (say, a
| varistor that blows the existing fuse) and it prevents a
| catastrophic failure.
| immibis wrote:
| But they want you to have to buy another one.
| hyperhello wrote:
| Why does this kind of comment get downvoted that
| pinpoints the actual motivation? We just pretend that
| planned obsolescence is history.
| majorchord wrote:
| At least in parent's case, probably because the vast
| majority of their comments are black-and-white hot takes
| that are always downvoted regardless. And they basically
| never respond when asked for any sources.
| jama211 wrote:
| Because it's an extreme claim backed up with no evidence.
| Hanlon's razor applies here.
| ranger_danger wrote:
| Also see Hitchens' razor and Russel's teapot.
| saghm wrote:
| To me, 220 sounds 20 like lower than 240. I have a hunch that
| this might be a common perception.
| geocar wrote:
| Really?
|
| I have all sorts of electronics that say everything from
| 208V - 240V that all go in the wall, so I think all those
| numbers are probably close to each other in whatever a volt
| is.
|
| I think if I'm worried about a limit of some kind, being
| within 5% of that limit seems like I might as well be over-
| limit if the _commonly seen_ distribution I see in my house
| is greater than 15%
| cjbgkagh wrote:
| I have a lot of electronics that accept 100-240v doesn't
| mean I think they're close together, just that they have
| compensating mechanisms to handle such voltages.
|
| The margins are generally lower for higher power devices
| because the electronics are more expensive. Thankfully
| these electronics in general are becoming cheaper which
| is one reason why they're ending up in the hands of
| people inexperienced with them.
|
| Also try to tell someone they need an extra 30% in margin
| and often they'll think they're being upsold.
| geocar wrote:
| > I have a lot of electronics that accept 100-240v
| doesn't mean I think they're close together, just that
| they have compensating mechanisms to handle such
| voltages.
|
| I bet you also have a lot of electronics that don't
| though, and those that do probably say so.
|
| My kitchen mixers, dishwasher, washing machine, driers,
| rice cooker, refrigerators, sauna, and pool pump aren't
| that tolerant by a long shot. I've got a few computers
| with a switch on the back to choose between 220v and
| 110v.
|
| Plugging something that takes 110v into my house breaks
| the thing, so I've learned to check.
|
| But I don't have anything that's 208v that can't go into
| the house. So I think whatever the situation is with
| volts, within 15% is "basically the same", so coming
| within 15% of the rated limit, is probably just like
| exceeding the limit by 15%.
|
| And so this is why I would not expect something at 146V
| to be under the safety limit of 150V.
|
| > Also try to tell someone they need an extra 30% in
| margin and often they'll think they're being upsold.
|
| Where do you get 30%?
| cjbgkagh wrote:
| You're listing things that are high powered and or old.
| Modern PSUs don't have that switch. While it's in the
| early stages I expect more white goods to switch to BLDC
| motors which will likely use voltage transformers that'll
| support the 110-240v.
|
| People generally are not lugging white goods
| internationally, the average persons experience with
| different voltages is for laptop and phone chargers when
| they travel.
|
| But for the matter at hand, the margin mentioned is
| needed on the solar systems, this is where the inverters
| can get expensive, which is why it can look like an
| unnecessary upsell to people who've never blown a device
| before.
| numpad0 wrote:
| > Idk. I don't have a PHD, but 220V sounds like 240V to me. I
| wouldn't do this.
|
| 220[Vrms] * 1.414 = 311[Vp-p] btw. HOW!?
| rzzzt wrote:
| AC wiggles and wobbles.
| mazurnification wrote:
| So the issue is that 220V is nominal in China, 230V nominal
| in UE and 240V is UK/part of Australia. So if anyone is
| preparing product for global market (as most are doing now)
| more likely then not will support all of this voltages.
| Thus is kind of normal (but wrong) to assume 220V sounds
| like 240V.
| adrian_b wrote:
| When the voltage was unified in UE, the nominal value was
| set to the median of 230 V, but its tolerance was raised
| from 10% to 15%, so that the new maximum peak value of
| 230V + 15% will match the old value of 240 V + 10%.
|
| So now for all 220/230/240 V standards you have the same
| maximum voltage value that is used for electrical designs
| (about 265 V effective), so they are equivalent,
| regardless of the name.
| gus_massa wrote:
| Many charguers are now 100-240V, 50-60Hz, that is close
| to pluggable anywhere on Earth. (I burned one or two a
| long time ago, when I forgot to check and used a 120V
| transformed here with 220V)
| rzzzt wrote:
| Same thing happened to PC PSUs. I don't think there is a
| recent unit that still has the self-destruct voltage
| selector switch which pops them if you are in 230V land
| (and the switch is set to the smaller setting).
| adrian_b wrote:
| Besides the ratio between the peak and effective value, you
| must also account for the standard tolerance of the nominal
| value.
|
| The actual maximum peak voltage for the European mains, is
| 230 V * 1.15 * sqrt(2), because of a 15% tolerance. That is
| about 375 V. With a small safety margin, the minimum
| voltage rating for components connected to 230 V a.k.a. 220
| V is of 400 volt.
| Zanfa wrote:
| This is 100% on the manufacturer if they intentionally chose to
| highlight the "best case" 150V, rather than the 120V lower end.
| Especially without any additional safety mechanisms.
| rcxdude wrote:
| The article presents it oddly, it's not that the converter
| maximum input gets lower, it's the solar panel output that
| gets higher from the nominal quoted value (which is _not_ a
| maximum, and not really intended to be used as such).
| Derating your converter is equivalent for the purposes of
| ensuring margins, but it implies the issue is in the wrong
| place.
| lazide wrote:
| The idea of safety margins has died under the more pressing
| type - profit margins.
| Pet_Ant wrote:
| Your safety margin is my profit margin.
|
| - Mr MBA
| Workaccount2 wrote:
| The failsafe circuit to protect against this (over
| voltage condition) is maybe $3 and incredibly routine in
| anything with power. I would bet everything that it is in
| there.
|
| What's most likely though is that the fuse is also
| internal, and externally the unit will appear bricked.
| namibj wrote:
| Your converter doesn't need to like the voltage, it just
| can't break from it. In fact, if it's the type that shorts
| the panels for curtailing, it should be happy to just run
| them at the highest voltage it's comfortable with, loosing
| a few percent generation during exceptionally cold days.
| jacquesm wrote:
| > it just can't break from it
|
| In fact, they can.
| huxley wrote:
| I think they meant "it just can't" in the sense of "it
| shouldn't under any circumstances"
| xg15 wrote:
| This feels a bit like the logic behind "do not put hamster in
| microwave" warning labels.
|
| I think if you work with electrical or electronic systems in
| practice, you learn pretty quickly to respect tolerances and
| that data sheets are a map, not the territory.
|
| Also, electrical installations are usually seen as a field that
| should be done by trained personnel, not arbitrary laymen home
| owners. So I think the appropriate reaction would be to remind
| people that they should hire an electrician to do the
| installation, if they don't have the necessary specialized
| knowledge themselves.
| harvey9 wrote:
| I have the impression these are consumer products so I would
| them to be designed to be installed by people who do not
| normally work with electrical systems. If they are only sold
| to tradesmen that would be different.
| xg15 wrote:
| Yeah, it would be important to understand who the company
| is intending to sell to or do the installation.
|
| Though the lines are often blurred, because I guess most
| companies would like to _sell_ directly to end customers,
| even if their product requires a professional to install.
|
| Even IKEA does this. You can go in and buy an electric
| stove and oven, grab them from the warehouse and take them
| home with you right there. But it's a bit of an illusion:
| You're still supposed to call an electrician to actually
| connect the things.
| krisoft wrote:
| > Yeah, it would be important to understand who the
| company is intending to sell to or do the installation
|
| You can do that by just reading the product page[1]. The
| delta pro, the equipment in question, looks like a plug-
| in appliance. It visually communicates that it is
| portable (by having a wheel and a handle) and by virtue
| of having a power lead connect to it it communicates that
| you can just plug it in. They further reinforce this by
| writing this: "Plug & Play home backup solution". "Easy
| installation with completely pre-wired Plug & play home
| backup solution" "The solution provides a convenient home
| battery system without rewiring or running dangerous
| extension cables through your home." "Plug directly into
| an AC wall outlet and make sure that the wall output
| current is more than 15A."
|
| And on top of that the manual[2] makes no mention of
| needing an electrician.
|
| In contrast an IKEA electric oven's product page[3]
| states this: "No plug is included. Installation to be
| carried out by a qualified installer." and then the
| manual[4] states "Installation, including water supply
| (if any) and electrical connections, and repairs must be
| carried out by a qualified technician."
|
| But of course nobody reads the manual. The big difference
| is that one comes with a plug while the other doesn't.
|
| 1: https://us.ecoflow.com/products/delta-pro-portable-
| power-sta...
|
| 2: https://websiteoss.ecoflow.com/cms/upload/2022/10/12/1
| 312845...
|
| 3: https://www.ikea.com/gb/en/p/mataelskare-forced-air-
| oven-ike...
|
| 4: https://www.ikea.com/in/en/manuals/matalskare-forced-
| air-ove...
| quickthrowman wrote:
| If you can do a code compliant installation, then you're
| the customer. If you can't, then I'd suggest hiring an
| electrician.
| beefnugs wrote:
| Actually if "you work with electrical or electronic systems
| in practice" you get pissed off at everything for how dumb it
| all is: 12V DC batteries are more like 14 nominal? AC wall
| plugs dip voltage when printers turn on, random equipment you
| arent even sure in the building can trigger UPSes based on
| unknown settings in the device? International standards and
| communication protocols mean nothing as "a standard" because
| each company has their own entire list of bugs/implementation
| mistakes. All the international enforcement certifications
| care way too much about inconsequential bullshit and miss all
| the true showstopping problems in most industries?
|
| This world is amazing anything runs at all. The slightest
| addition of complexity is causing everything to fail now.
|
| Modern computers are less reliable than ever, some companies
| have decided to REMOVE the pinhole bios reset (that has been
| around for 30 years) at the same time as things are buggier
| now and dont boot again until you physically unplug the bios
| battery deep inside and hard to get to.
| xg15 wrote:
| Spoken like a true professional!
| amelius wrote:
| The modern engineer:
|
| It works! OK, stop touching it. We don't want to break it.
| Workaccount2 wrote:
| This is what makes software engineering so seductive,
| everything works exactly as it was designed to (whether
| intended or not). Imagine trying to program for computers
| with memory that drifts values progressively more as it
| wears down.
| boothby wrote:
| Software engineering _sucks_ compared to pure
| mathematics. Back when I was in uni, everything always
| did exactly what it said on the label.
| emn13 wrote:
| So on the one hand we have a product which isn't even
| remotely designed for the use case (hamsters), and during
| normal use shows obvious behaviour (cooking) that should
| imply risk to said hamsters. On the other side, we have a
| product designed to be installed in an electrical system, and
| shows no signs during normal use that it's installed
| unsafely, and where the advertised specs are not actually
| safe for normal usage.
|
| Whether or not the company in this case shares some or most
| of the blame with novice users - the analogy is not a great
| one.
| nanomonkey wrote:
| Microwaves were originally specifically invented to
| microwave frozen hamsters:
|
| https://interestingengineering.com/videos/1950s-reanimating
| -...
| adiabatichottub wrote:
| As Doc Brown would say, "Great Scott!"
| amelius wrote:
| > make it more resiliant, rather than blaming customers
|
| Yeah, this sounds very much like "you're holding it wrong".
| bayindirh wrote:
| They can add a relay, I guess? Voltage monitoring is cheap.
| Relays might push price above a bit, but it's a worthy
| premium to pay in my book.
| abcd_f wrote:
| I read it as a problem with _solar panel_ voltage going over
| declared threshold of 37v in certain meteo conditions.
|
| That is the issue is with the wrong labeling of things that are
| being plugged into this vendor's device, not the vendor's own
| labeling.
| bayindirh wrote:
| If something can go wrong, it _will_ go wrong. So both
| parties should note that something can go wrong and point to
| that something.
| TeMPOraL wrote:
| I believe the vendor here produces both the device and the
| panels being plugged into it, and while they also supply
| other vendors' panels, they seem concerned primarily with
| customers who buy all components from them and then
| experience this failure.
|
| I agree the labeling is an issue here, but the solution must
| come from the wider industry or regulatory bodies; the
| alternative is for vendors to switch to their own pseudo-
| units to internalize the math, which would not be good for
| customers either - think "ACME Generator2000 accepts up to 4
| Power Units of input; each ACME SuperEco Panel supplies 1
| Power Unit, or 1.5 Power Units if you're in Canada...".
|
| Saving users from having to do a little thinking to not brick
| their device is a tried-and-true excuse for vendor lock-in in
| our industry :).
| ninalanyon wrote:
| Why not label the panel with the maximum possible voltage
| that it can produce? Or even have a little table showing
| the maximum possible voltage at various ambient
| temperatures. It's not as if there isn't room on the back
| of the panel for a big enough label.
| marcosdumay wrote:
| The entire industry has standardized in having "typical"
| and "maximum" values decades ago. That problem there is
| completely self-imposed.
| lostlogin wrote:
| The flip side of this is also dumb labelling. 'Product
| may contain traces of nuts'.
|
| Completely unhelpful to those that need the info.
| cowsandmilk wrote:
| Considering the electric code has an 80% rule for loads, anyone
| assuming they can use 100% of what is on a label probably
| should not be doing electrical work.
| immibis wrote:
| Very true. My computer says 240V on it, so I should only use
| it up to 192V.
| rcxdude wrote:
| No, you just shouldn't _assume_ that that 's the case. In
| the case of a computer and mains, both of those are nominal
| voltages and there will be a range of voltages which are
| expected to function, and if you want to check for sure,
| you should check those ranges.
| lazide wrote:
| Interestingly, the peak voltage of 240V AC (typical) is
| 330ish+ volts.
|
| Typical house wiring is required to handle 600v due to
| voltage transients and wear and tear.
|
| So any component rated to 240V dc will fail immediately on
| AC, and even 400-500V DC is not a good idea.
|
| I guess there is a reason there is a whole category of
| engineers for this kind of thing.
| stephen_g wrote:
| Which electrical code? They vary from country to country and
| even state/province in some countries!
| quickthrowman wrote:
| I agree with you, but. The NEC has an 80% rule for continuous
| loads (over 3 hours) that use a typical circuit breaker as
| overcurrent protection. If you use fuses or a 100% rated
| breaker as your over current protection, then you can use all
| of the available ampacity. Anyways, devices that use a 15A
| receptacle (for example) will not draw more than 12A
| continuous if they're meant to run continuously (3 hours or
| longer).
|
| https://www.se.com/us/en/faqs/FA104355/
| cameronh90 wrote:
| I don't know about the components they're selling, but with
| electronic components, it's on the buyer to properly read the
| data sheet and understand what the quoted nominal specs mean.
|
| Unless it's safety critical, you usually _don't want_ a system
| with a bunch of active electronics to prevent someone wiring it
| up wrong, because those components will interfere with whatever
| you're hooking it up to, such as the MPPT, the battery, or
| whatever else.
|
| This is like how AA batteries have a nominal voltage of 1.5V
| but the actual open circuit voltage is 0.9V~1.65V depending on
| charge level, temperature, etc. If you connect an AA to
| something that'll explode at a voltage of 1.55V, that's on you.
|
| Similarly if you buy a 470 ohm resistor, you will find in on
| the data sheet that's usually at 20degC. To know what it'll be
| at any other temperature, you'll need to use the temperature
| coefficient to calculate it.
| jama211 wrote:
| This isn't electronic components, this is sold as a consumer
| level gadget that anyone can use. No one expects a standard
| consumer to understand data sheets like that.
|
| You started off by saying you don't know about the components
| they're selling - but that turns out to be absolutely
| critical to understanding the context here.
|
| Either way, I can't believe they just let it fry the main
| board instead of having a sacrificial fuse or equivalent go
| first in these scenarios, whether it was a product aimed at
| professionals or not. It's just dumb.
| mschuster91 wrote:
| Maybe it would be a good idea to at least add a pair of MOSFETs
| (one for each rail, + and -) and a voltage meter? Like, the
| voltage doesn't rise to maximum instantaneously, there should
| be ample of time to detect voltage rising to a critical amount.
|
| So say, the input is rated for 150V, spec the components to
| sustain 180V, and trigger the MOSFETs to disconnect the panels
| at > 160V.
|
| And maybe also add a big ass buffer capacitor, that can be used
| to soak up a bit more energy in the case of an inrush spike
| before the MOSFETs actually disconnect.
| privatelypublic wrote:
| MosFET's or IGBTs are likely what failed. And, capacitance is
| something you do not want on a string of PV.
|
| DC starts getting really nasty to deal with somewhere between
| 36-52v, with 150v of panels not being something joe-blow
| should be able to buy on amazon. Designing these systems to
| be safe is difficult.
| hathawsh wrote:
| A few years ago, I plugged a single 100W solar panel into a
| battery pack that advertised it accepts 18 volts. I left it
| plugged in, on my deck, for hours. When I came back, there was a
| foul smell and some parts of the battery pack had turned black,
| apparently from getting charred. The battery pack no longer
| worked at all. I was very fortunate that only the control circuit
| had been destroyed and the battery cells (and my deck) had not
| been touched.
|
| Lesson learned: don't skimp on Li-ion battery packs!
|
| Also, I have a question about this article. Don't EcoFlow battery
| packs have a circuit that checks the incoming voltage and
| automatically shuts off charging if the voltage is too high? I
| would also expect a loud alert.
| righthand wrote:
| Current title is actually a subtitle. Actual title:
|
| `Solar Panels + Cold = A Potential Problem`
| marginalia_nu wrote:
| To be honest I went into it half expecting it to be about papal
| elections[1].
|
| [1] https://theconversation.com/conclave-the-chemistry-behind-
| th...
| tgv wrote:
| The subtitle is, though, and I do find a problem with it. There
| might be someone out there (possibly not sober) who thinks
| "Magic smoke? Let's see some!" It also somewhat distorts the
| original. It should be more like "unless you want the magic
| smoke to escape." The smoke's magic properties are gone once
| that happens. At least, nobody has ever proven the escapee
| smoke has any.
| tomhow wrote:
| Thanks, we've updated the HN title to the article's main title
| now.
| bob1029 wrote:
| I never tried the solar charging on my ecoflow so this fragility
| surprises me a bit.
|
| I've been able to run laundry in a machine with a 1/2hp motor
| using the inverter side on multiple occasions. No smoke or funny
| smells. My 2200w generator would trip out the instant the spin
| cycle tried to start.
| dotancohen wrote:
| Slightly OT, but how big of a capacitor would be needed to
| smooth out those current spikes? Solar-friendly could be a
| selling point for some appliances.
|
| I wonder if such a capacitor could even be retrofitted.
| namibj wrote:
| Don't bother; at that point just plug them into 200~300 V DC
| right to the battery (with just fuse and meter between, no
| need for any conversion, the washer motor controller that'd
| be needed to utilize a capacitor for smoothing these spikes
| would do just fine on a reasonable battery charge/discharge
| voltage spread.
| dotancohen wrote:
| Do any home battery systems, or home appliances, actually
| support this?
| bob1029 wrote:
| A capacitor wouldn't help in this case. They're most useful
| when you need to overcome transient situations like a locked
| rotor, not when you have a heavy drum that needs to be spun
| up from zero. During this phase the machine can consume well
| over 2kW of power for a few seconds. The circuit is rated for
| _continuous_ 15A, but it has no problem supplying 20 or 25
| for a brief period of time.
| dotancohen wrote:
| I'm sure that home mains would have no problem, but a solar
| installation might. Would a small li-ion help smooth over
| those amperage hills?
| jacquesm wrote:
| It would help at noon, when usually inverters make so
| much power they push the local grid to saturation which
| causes them to disconnect from the grid for a while.
| There are different rules for this for different
| localities, typically the installer will pick the regime
| appropriate for the local grid. Where I live (NL) the
| voltage is allowed to hit 253V for up to a minute, if it
| takes longer than that my inverters will switch off.
| That's a requirement to pass inspection, if your inverter
| can not do this then that's an automatic fail.
|
| There are 'home batteries' that store power for practical
| reasons up to a day, maybe two. They are useful for
| sunny/cloudy conditions to maximize the amount of power
| locally consumed. But battery storage and retrieval isn't
| free and so far - at least, for my installation - this
| does not make economic sense. But another factor of two
| in price drop for my preferred chemistry and it
| definitely would make sense and then I would probably
| install about 20KWh worth of capacity. The trick then
| becomes to balance power sent to the grid and sent to the
| battery so that you maximize the utility of the grid in
| order not to wear out the battery prematurely. That means
| cycling the battery between 70 and 90% state-of-charge
| for Lithium-Ion. I'd much rather have Lithium Titanate so
| that is what I'll be holding out for, they are already
| available, but still too expensive. But they're much
| safer and have far better charge/discharge curves and
| life-span.
| dotancohen wrote:
| I actually meant a small li-ion inside the appliance, to
| smooth out the load. Do any batteries support 20C or 30C?
| That seems like enough to smooth such a load.
| jacquesm wrote:
| That's a very complex and potentially dangerous device.
| rini17 wrote:
| The solar panel with inverter does not have any inertia so it
| can survive power spikes more easily, can lower the voltage
| till it's over. The generator on the other hand has physical
| rotating parts that could be damaged by sudden torque asked by
| increased load. Of course it could be mitigated with additional
| "soft start" circuitry on the motor but that's usually not
| included. Not capacitor alone please, you risk more damage.
| uyzstvqs wrote:
| Sounds to me like someone is misrepresenting their products. A
| solar panel's VoC should be its maximum possible output in ideal
| conditions (open circuit). If that's under your product's maximum
| input voltage, it should be no problem. Ever.
|
| Is EcoFlow advertising a higher input voltage than their products
| can actually take, assuming most people won't actually reach it
| due to temperature inefficiencies? That'd be false marketing, and
| it'd make this article manipulative, false blaming of the
| customer.
| taneq wrote:
| What does "maximum possible voltage" mean for a solar panel? Do
| you include things like cloud edge effect (which increases
| incident light beyond direct sunlight?) What about installs
| with a nearby window reflecting light onto the panel? Do you
| include ultra-cold environments (which will reduce the
| resistance and therefore often increase voltage, although
| admittedly not, I think, Voc)?
| GLdRH wrote:
| Obviously you include everything, otherwise it wouldn't be a
| maximum. You can define a minimum temperature for this, of
| course, but the customer should know about it.
| numpad0 wrote:
| There's no theoretical maximum voltages for solar panels
| like there kind of is for batteries. They're just giant
| array of photodiodes and they just generate whatever
| voltage potentials proportionate to amount of lights
| received.
|
| You could produce a "max voltage flying low earth orbit
| over Gobi with no shadows from Starlinks" value, but that's
| just the value for circumstantial most absurd situation you
| happened to have come up with, not a guaranteed theoretical
| maximum.
| jimnotgym wrote:
| So it is doubly important that all equipment downstream
| has overvoltage protection?
|
| In fact considering there is no theoretical maximum, it
| would be downright negligent not to have overvoltage
| protection
| numpad0 wrote:
| Yeah, billowing magic smoke just sounds wrong. No
| disagreement there.
| mrob wrote:
| There is a theoretical maximum: the open circuit voltage
| of a single photovoltaic junction cannot exceed the
| bandgap of the semiconductor used, no matter how much
| light you apply. The manufacturer knows the semiconductor
| used and the number of junctions in series.
| adrian_b wrote:
| The current is what varies proportionally with the amount
| of light received.
|
| The open-circuit voltage depends mostly on the structure
| of the solar cells and on the temperature. It has only a
| very weak (logarithmic) dependence on the amount of light
| received.
|
| The voltage that you measure at the output depends on the
| open-circuit voltage, on the amount of light received and
| on the amount of current that you draw from the panel.
|
| The maximum open circuit voltage for a solar cell is easy
| to estimate, because it happens at the minimum
| temperature for which it is designed and the maximum
| solar illumination. It can be exceeded only using a light
| concentrator that projects on the panel light collected
| from a much greater area.
| namibj wrote:
| They produce current until the diodes start conducting
| given the forward voltage, as they'll take any current
| you don't extract off of your hands.
|
| Of course if you want to extract maximum power you have
| to balance the higher worth of the current you take
| against the loss of current to the diode forward
| conduction.
| uyzstvqs wrote:
| VoC is the maximum potential voltage a cell is physically
| capable of producing. It does not consider real-world
| conditions. Rather, real-world conditions cause the solar
| panel's output voltage to be somewhere between 0 and its VoC.
| sunshinesnacks wrote:
| Voc is just the open circuit voltage measured at the
| terminals (plugs). "Nameplate" Voc is at standard test
| conditions (STC) of 1000 W/m^2, 25 deg C cell temperature,
| and a standard are mass/spectrum. The combo of 1000 W/m^2
| and 25 C cell temp is not common in the real world in most
| climates, but still happens. Even relatively hot climates
| can have times in winter that exceed nameplate Voc if
| inverters turn off (making the panels go to open circuit).
| guerby wrote:
| All solar panel datasheet have temp coefficient, eg for one
| random ecoflow solar panel: Temperature
| Coefficient Specifications TKPower -(0.39+-0.02)%/k
| TKVoltage -(0.33+-0.03)%/k TKCurrent +(0.06+-0.015)%/k
|
| source
| https://websiteoss.ecoflow.com/cms/upload/2022/10/15/-139121...
|
| STC ("standard testing conditions" for solar panels) is 25C so
| if it's freezing 0C you have 25 multiplied by 0.33 Volt = 8.25
| Volt more than STC in open circuit situation.
|
| Unfortunately inverter manufacturers seldom document how many
| Volt will destroy the MPPT and up to how many Volt the MPPT
| will safely turn off by itself before breaking.
| namibj wrote:
| Not to mention a fail-safe MPPT would/should just crowbar the
| input if there's any potential for overvoltage.
|
| Solar panels are current sources that waste their power into
| a long string of silicon PIN diodes that eventually reach
| their forward voltage and begin to eat up all that juicy
| current. You can just take the current and keep the voltage
| as low as you want, just make sure to take all the current or
| it's voltage will rise to let the diodes take the current you
| aren't using.
| taneq wrote:
| What we're seeing here is the mismatch between component level
| specs and end user ratings. A device which is rated to 24V input
| power will probably tolerate up to 32V and it surviving 60V would
| not be uncommon. A component with a Vmax of 24V probably explodes
| if it sees 25V.
| gsf_emergency_2 wrote:
| To flip this into a potential _solution_ to a wider problem--
| global thermal balance-- combine solar panels with radiative
| cooling.
|
| https://www.sciencedirect.com/science/article/pii/S258900422...
|
| https://www.pv-magazine.com/2025/01/13/daytime-radiative-coo...
| pfdietz wrote:
| https://web.stanford.edu/group/fan/publication/Li_ACSPhotoni...
| Faaak wrote:
| Last year, I did yet another PV install at a friends house. While
| plugging the SMA inverter to the solar field (600V), I fucked up
| and inverted plus & minus.
|
| Nothing happened. I read the manual and realised that SMA
| inverters are protected against reverse polarity. Yeah, a bit
| more expensive, but well worth it
| namibj wrote:
| I'm more surprised you managed to plug them in reversed; did
| you have good reason to avoid the polarized semi-pwrmanently-
| latching connects that most panels ship with?
| phkahler wrote:
| >> With mixed solar panels, lowest volts in parallel strands
| prevails
|
| If a panel can hold down the voltage of others, their device
| should be able to do the same.
|
| Sounds like a corner case their software can't handle. Even so,
| the hardware should not go up in smoke.
| myself248 wrote:
| This is what happens when something goes mainstream. The
| background knowledge that "everybody knows" when it's niche,
| because only turbo-nerds are into it, simply isn't common sense
| for everybody in the wider population.
|
| Back when Home Power magazine started up, the panels were super
| expensive, and squeezing out every watt was important. Since high
| temperatures decrease voltage and output, keeping the panels cool
| (while baking in the sun!) was top-of-mind for every
| installation. And right along with learning that critical
| consideration, everyone also learned the caveat that in the
| bitter cold, that very same phenomenon means they can produce
| significantly _more_. Temperature coefficient was simply
| something "everyone knew".
|
| Now they're so cheap nobody cares. The magazine shut down because
| "alternative power" and EVs aren't exactly alternative anymore,
| you can buy one off the dealer's lot, it's nuts. And the panels
| are crazy cheap now. If you lose 10% because the panels are hot,
| it's likely cheaper to just buy 10% more panels, than to redesign
| your support brackets to allow better airflow. But nobody
| highlights the phenomenon behind the efficiency loss.
|
| "Everybody knew" that the ratings on the panel are at Standard
| Test Conditions: 25degC and 1000W/m2. That's almost never the
| conditions in the real world, but it establishes a legal baseline
| whereby panels can be compared apples-to-apples and advertising
| kept honest (if anyone cared), but deviate from STC and output
| will go down, or up. Again, ask _today 's_ consumer what the
| ratings on the label mean, and most of 'em have never heard of
| STC nor could define how the nameplate wattage is just one point
| on a curve.
|
| Is this the panel manufacturer's fault? They're labeling things
| precisely the same as they've labeled them for 40-plus years.
| (Perhaps there's even more data on the panel label now, as Vmp
| and Imp are typically specified now, and they weren't always
| universal.)
|
| Edit to add: The label doesn't typically specify the temperature
| coefficient, but for every panel I've checked, _it is in the
| datasheet_. But who reads datasheets?
|
| Is it the inverter manufacturer's fault? They're labeling things
| precisely the same as they've labeled them for 40-plus years. The
| input max is a hard limit where the silicon can take no more, and
| there's a certain amount of headroom required between that and
| the panels' max, _after_ compensating for temperature
| coefficient. Of course you calculate your panel voltage for _your
| local conditions_ before comparing it to the inverter input, duh!
|
| Everyone knows that! Except now they don't.
| jacquesm wrote:
| The input max is for most inverters on the market now a
| setpoint where they will simply disconnect, stop generating
| power and go into an error state that you need to hard-reset if
| you want to use the inverter again. It's pretty typical to have
| a 1000V hard limit on a nominally 800V or 600V system. If
| you're going to ride close to the limit then on some days you
| will see overvoltage and disconnects. So it is something you
| simply should not do. But people think that if the label says
| 1000V then 990V total nominal panel voltage should be fine,
| which it obviously is not. Panels are analog devices, they will
| produce an open circuit voltage much higher than their nominal
| use voltage and when you're on a switched mode inverter that
| means that the average voltage may well be 'in spec' but the
| voltage from one millisecond to another may well be outside of
| that if the system was built 'on the edge'. And because
| inverters have to take the grid side into account as well (they
| are not allowed to exceed certain voltages) there is always the
| risk of not being able to load the panels sufficiently to get
| the voltage to drop. So you should side your system so that the
| open loop voltage of your panels under ideal conditions is
| still comfortably lower than the max input voltage of the
| inverter. 800V nominal is pretty close to that limit, 700 is
| better and 600 is playing it safe.
|
| I think one of the main reasons why installers tend to
| overprovision voltage wise is that they count on the inverters
| switching off the whole string every now and then versus being
| able to make more power without a lot of additional wiring
| under normal conditions. The net effect of that is positive.
|
| Low quality inverters (the ones without the ability to
| disconnect the HV side autonomously) should be avoided like the
| plague anyway, those are simply unsafe and as far as I am
| concerned should not be allowed for re-sale at all.
|
| My own system can make 17KW on a very good day in March at 1 pm
| or so, but normally it is closer to 12KW even in the summer. So
| those peaks are actually substantially over the normal output.
| Over a given day the average is about 5 KW or so from sunrise
| to sundown, and those first and last hours hardly contribute.
| metalman wrote:
| Where to start, eh! So most everything to do with off grid
| specifications can be listed as "nominal", ish, depending on,
| etc.Not knowing this means that persistance will provide the
| circumstance to be educated. There are a number of ways to get
| things wrong and melt stuff, or get hurt. Batteries should always
| be treated as unpredictable dangerous beasts, happy as a clam if
| they are treated just right, but capable of producing trouble and
| disaster, or just del8vering a viscious bite to the unsuspecting
| and surviving to do it again. A 48volt (nominal) battery bank
| will happily turn the required 10mm wrench into single
| demonstration of a wide range of metelurgical and other
| phenomina. For fun on a cold morning take the leads from a 3 kw
| solar array, off, and then strike the wires to produce a realy
| big fat arc, h3y hey! The simple fact, that I tell enthused,nice,
| but clearly unprepared people who express interest in "off grid",
| is that I do it, but it's not for everybody, as there is a
| significant technical learning curve, plus the required physical
| skills to mount panels, run wireing, deal with battery banks,set
| up the systems, and if costs are to be kept to a minimum then
| source parts from distributors or import directly.
| bryanlarsen wrote:
| On the other hand, properly designed solar can do surprisingly
| well surprisingly far north.
|
| Here's one in Tromso Norway, well north of the Arctic Circle.
|
| https://cleantechnica.com/2025/09/27/bifacial-rooftop-vertic...
| sowbug wrote:
| I can imagine future solar panels sending spec data to the MPPT
| using Power Line Communication (PLC), allowing the system to shut
| itself down gracefully rather than dying. Rapid-shutdown systems
| already send keepalives using PLC today.
|
| But then it goes all Black Mirror, with manufacturers restricting
| solar-panel operation to approved devices only, and UIDs being
| used to enhance shareholder value through recurring subscription
| revenue.
| namibj wrote:
| The MPPT could just short them out and it'd be fine; solar
| panels are a current source with a huge string of non-light-
| emitting diodes wired in parallel with the output happy to soak
| up any excess current around their forward voltage.
|
| (Technically the current source in question is _within_ the
| diode's junction capacitance.)
| EcommerceFlow wrote:
| Cool article. The real solution to this is have huge arrays in
| the desert and move the energy north, which is 100% possible.
| adrianN wrote:
| There are a lot of possible things. The question is which is
| the easiest to get financing for.
| phyzome wrote:
| I don't think that addresses the thing that the article is
| actually about...
| cornstalks wrote:
| A lot of people here are saying things are mislabeled, but every
| single solar panel comes with a datasheet that shows its Voc and
| temperature coefficient.
|
| Solar panel manufactures can't give you a hard maximum on voltage
| because temperature will make that vary. Anyone who is buying
| solar panels without understanding the temperature coefficient
| shouldn't be buying solar panels. It's not hard to understand and
| there are hundreds of guides out there explaining it if you just
| search for terms on the datasheet.
| 1970-01-01 wrote:
| >Plugging in four 400w solar panels in series is similar to
| filling your gasoline powered car with diesel and wondering why
| the car manufacturer isn't replacing your new car.
|
| Ok, that is a very bad answer. Diesel fuel contains more amounts
| of energy per drop as gasoline, but that doesn't mean engine
| damage will result. Diesel fuel will not damage an engine if you
| were stupid enough to get it wrong at the pump. It will simply
| refuse to cycle until the diesel fuel is pumped out and the
| correct fuel is pumped in.
| stockresearcher wrote:
| Maybe it's different in the rest of the world (I doubt it), but
| the fuel nozzles for gasoline and diesel are different. You
| can't put a diesel nozzle into the opening on a gasoline car,
| so it's rather difficult to fill a gasoline car with diesel
| fuel.
|
| The other way around is possible. You can fill a diesel tank
| with gasoline. Whether it destroys the engine or not depends on
| how much gasoline you put in. A gallon or two that is then
| diluted by filling the rest of the tank with diesel is not
| likely to cause any lasting damage. If you fill a tank 3/4 of
| the way with gasoline and try running it in a diesel you are
| probably going to need a new engine.
|
| So yeah, the analogy is not good. Slightly exceeding the rated
| voltage and breaking the whole thing is usually not the same as
| putting a little gasoline in your diesel tank.
| nerdralph wrote:
| Calculating temperature correction is in both the NEC and CEC.
| Here's the CEC version:
|
| 64-202 Voltage of solar photovoltaic systems (see Appendix B)
|
| 1) The maximum photovoltaic source and output circuit voltage
| shall be the rated open-circuit voltage of the photovoltaic power
| source multiplied by 125%.
|
| 2) Notwithstanding Subrule 1), the maximum photovoltaic source
| and output circuit voltage shall be permitted to be calculated
| using a) the rated open-circuit voltage of the photovoltaic power
| source; b) the difference between 25 degC and the lowest expected
| daily minimum temperature; and c) the voltage temperature
| coefficient as specified by the manufacturer.
| PaulKeeble wrote:
| The cause of this problem is the standards for Solar Panels, that
| has the outputs measured at 25C so they are comparable with each
| other. The specification sheets for panels do list their peak
| voltage in other conditions but all the advertising is based on
| the standard. Solar installers know about this and size
| accordingly but your average consumer doesn't and is very quickly
| going to get into trouble with this.
|
| I think what Delta needs to do here is accept that the standards
| mean all Solar will be sold this way and appropriately oversize
| the inverter so that it can cope with -10C sunny days. Yes its
| annoying for them but the reality is devices sold to people who
| don't know how all this works need to compensate for lack of
| expert knowledge in its user base.
| jacquesm wrote:
| This is not a problem in a properly dimensioned system at all.
|
| It is still well within the 'engineering reserve'. Solar panels
| produce the most power in mid March, when they are cooled very
| well by the ambient air but the sun is already lining up nicely
| with the panels at mid-day. But those conditions are pretty rare,
| and most inverters will handle this gracefully by simply dumping
| some of the excess power as heat - or in the better ones, by
| simply chopping the input voltage at a high frequency. This
| allows for very fine control over the average power and will help
| to keep the voltage under the isolation break down voltage (which
| usually is a very large factor over the voltages that you see in
| practice).
|
| My own system is 50 panels, 1000V maximum on panels that
| nominally produce up to 100V, so I never have more than 8 of them
| in series. That leaves 200V to play with and I've never seen it
| get close to that 1000V. The inverters are easily capable of
| dealing with this and if the strings were to ever exceed 1000V
| then the inverters would simply disconnect those strings with
| their internal disconnect relays.
|
| So, in closing: don't run your system 'on the limit' or rare
| conditions will push it over the limit. But even if you do:
| inverters are fairly bullet proof nowadays and if you over-volt
| the input the vast majority of the ones that you can normally buy
| are going to just switch off and move to an error state that will
| require you to power them down before they will be usable again.
| mulle_nat wrote:
| Can anyone comment on the "You can exceed the amperage specs" ? I
| made myself a little case study using 4x1W panels and using them
| in series and parallel. I got the distinct impression that
| running panels in parallel is better in not so bright conditions
| compared to a single panel. Whereas a serial configuration made
| it worse. Since the sun doesn't shine here that much. Running in
| parallel seems to be preferable, but it would slightly exceed the
| amperage spec of a few converter i sampled.
| jacquesm wrote:
| The problem is usually shading, not so much the capacity of the
| wiring, though, if you try hard enough you can exceed the
| rating of the final stretch of wiring to the inverter (or the
| little pigtail in the inverter if you connect all of the
| strings at max voltage/amperage). Shading can really upset the
| current flow in a set of parallel/series connected panels and
| can cause local hotspots due to overcurrent. Usually inverters
| are pretty smart about this and they'll detect that you are
| pushing it further than is responsible and they will just
| switch off. I've purposefully triggered such conditions to
| ensure my installation is safe and I was pretty impressed with
| how utterly painless fault detection, isolation and recovery
| are in modern inverters. I also had an older one and there it
| definitely wasn't all that friendly, to the point that the
| whole thing had to be hard disconnected from the grid before it
| would work again.
| jama211 wrote:
| Ecoflow fucked up, more news at 11.
| jlundberg wrote:
| Our installation from 2017 of 40 panels work great here in the
| middle of Sweden.
|
| Covered in snow over the winter and generate little power
| November-February but rest of the year we have fine power output,
| with peaks May-July (obviously).
| londons_explore wrote:
| Solar inverters could be designed smarter.
|
| Today's inverters have a volt limit and an amp limit and you may
| stay within both.
|
| But physics doesn't require that - you could instead design a
| solar inverter where you could stay within _either_!
|
| It would work by detecting when one limit (volts or amps) was
| about to be exceeded, and pushing the operational point away from
| there. Remember that for solar there are _two_ zero power - ie
| safe - points. I=0 is the usual one, but V=0 (ie short circuit)
| is equally safe.
|
| So this hypothetical inverter would operate between one of the
| safe points and the max power point.
|
| Obviously whilst installing the system and humans unplugging
| wires, the V=0, huge current safe point is impractical. But
| that's why you have breakers.
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