Subj : Re: pi5 psu?
To   : All
From : Chris Townley
Date : Mon Oct 13 2025 18:32:29

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

-- 
Chris

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