[NANOG] Re: Small Capacity UPS

[Gary Sparkes via NANOG <nanog () lists nanog org>]

32-35c is perfectly acceptable, not too high at all.

From: Mark Tinka <mark@tinka.africa>
Sent: Monday, April 14, 2025 5:53 AM
To: Vasilenko Eduard <vasilenko.eduard () huawei com>; Gary Sparkes <gary () kisaracorporation com>; North American 
Network Operators Group <nanog () lists nanog org>
Subject: Re: [NANOG] Re: Small Capacity UPS


On 4/14/25 08:45, Vasilenko Eduard wrote:
Hi Mark,
You are talking a lot about how damaging temperature is to the battery. I do not remember you or Gary saying that 50 
degrees Celsius is already not good.
But how could it happen in the home environment?!?
People like 22+-2 – they would start to do something urgently if the temperature reached 28.
Home has no source for 100kWt to charge really fast, hence, the current is relatively small.

In most homes with a battery backup, it is typically installed in the garage, shed or basement if one exists.

Climate control in these places is not often a priority, e.g., parking your car in your garage after being out on the 
road comes both with heat off the body of the car, as well as heat being dissipated by the engine, brakes, discs, 
exhaust pipes, e.t.c. That can easily send a closed garage's temperature up several degrees if the garage is not 
running any form of active cooling.

Some installations in a shed will have, at least, an extractor to suck warm air out of the structure. But while that 
may lower the temperature, it's often not enough to keep it at 25°C, which is the most optimal for  Li-Ion batteries.

You don't need to charge a Li-Ion battery fast for the temperature to rise appreciably. Just charging an LFP battery at 
0.25C (so 25A) can raise cell temperature by 1 - 3 degrees for every 10% of SoC gained assuming room ambient room 
temperature.

For my installation, my battery is in my garage. In addition to fans and an extractor, I also have active cooling with 
an air conditioner. Going into our winter now, the a/c will no longer be needed since ambient temperatures will peak at 
about 10°C - 15°C, keeping the battery cells between 18°C - 25°C even during a 0.25C charge rate.

But during our summer, without active cooling, the cells will live between 32°C - 35°C, which is too high.

Mark.
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