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From: usenet@dolik.dev (Andriy D)
Newsgroups: comp.sys.raspberry-pi
Subject: Re: Backup power supply
Date: Fri, 15 Mar 2024 08:45:46 -0000 (UTC)
Organization: Hugayda Station
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Computer Nerd Kev <not@telling.you.invalid> wrote:
> Andriy D <usenet@dolik.dev> wrote:
>> The Natural Philosopher <tnp@invalid.invalid> wrote:
>>> On 14/03/2024 07:57, Andriy D wrote:
>>>> This is exactly my concern - I want this think up&running 24/7/365 and I don't want
>>>> it to burn my house down :)
>>>> I guess this is where you'd say 'risk' and 'price' are in a inverse relationship ;)
>>>> -- 
>>> It is entirely possible to trickle charge a lithium cell at uber low 
>>> risk, Essentially you want to current limit the supply at at one tenth 
>>> of the hourly capacity so e,g a 2200mAh celll would need to be charged 
>>> at no more than 220mA, and voltage limit the charge at 4.2V.
>> Majority of the schemes I've found so far suggest use of NiMH cells as 
>> they are less 'combustive'.
> 
> Indeed, but if the power requirements are low (a Pi Zero without any
> power-hungry USB/HDMI connections) then supercaps might be an easier
> option. Since then you don't need to worry about over-charging,
> which will still wear out NiMH, even if it doesn't then burn your
> house down.
I had this thought as well, as all I need is to have enough power to 
cover for a few seconds of a power outage or gracefully shutdown RPi if 
it's longer than that. Thanks for that link!

-- 

Cheers,
\aID