Subj : Re: pi5 psu?
To   : All
From : Pancho
Date : Tue Oct 14 2025 00:31:29

On 10/13/25 18:35, Chris Townley wrote:
> On 13/10/2025 18:32, Chris Townley wrote:
>> On 13/10/2025 18:20, Pancho wrote:
>>> On 10/12/25 16:03, Daniel James wrote:
>>>> On 09/10/2025 16:42, Mike Scott wrote:
>>>>> I've just installed rasp OS on a new pi5 for the first time. It 
>>>>> moans the psu is insufficient, and can't deliver 5A. But the psu 
>>>>> itself - a kosher raspberry pi one - claims it will deliver 5A/25W.
>>>>
>>>> That doesn't sound right.
>>>>
>>>> Raspberry Pi sell three different USB-C PSUs:
>>>>
>>>> - A 15W PSU for use with the Pi 4/400 only.
>>>> - A 27W PSU for use with the Pi5/500 (and 4/400)
>>>> - A 45W PSU which is like the 27W but more powerful and can power 
>>>> some laptops, etc.
>>>>
>>>> The 27W and 45W PSUs support the USB Power Delivery spec and will 
>>>> provide a range of powers/voltages after negotiation with the 
>>>> device. The 15W PSU provides only 5V/3A, and is stated to be 
>>>> inadequate for the Pi5 and later.
>>>>
>>>> There is no official "kosher" 25W PSU from Raspberry Pi.
>>>>
>>>
>>> I think the 27W PSU was the original official version.
>>>
>>> Also, it is worth making clear the rPi5 USB PD is unusual, it only 
>>> uses 5V and negotiates current up to 5A (which somehow = 27W).
>>>
>>>
>>> Whereas my normal USB PD plugs produce their specified high wattage 
>>> by boosting voltage, so they don't work with the rpi5 at all. Which 
>>> irritated me a lot when I found out.
>>
>> ISTR it can give other voltages, but the Pi5 will only negotiate 5V - 
>> or 5.1V I believe
> 
Yes, that's right, my statement was muddled.


>  From the spec: The available profiles are 9V, 3A; 12V, 2.25A; and 15V, 
> 1.8A, all limited to a maximum of 27W
> See https://www.raspberrypi.com/products/27w-power-supply/
> 

And 3A * 9v =27w, even if the rPi5 can't use it.

Hopefully the next round of Pi type devices will use more standard, 
higher voltage, USB PD. If my cheap USB plugs can do PD it shouldn't be 
too expensive to support?

--- PyGate Linux v1.0
 * Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

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