Subj : Re: pi5 psu?
To   : All
From : Chris Townley
Date : Mon Oct 13 2025 18:35:10

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

 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/


-- 
Chris

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