[NANOG] Re: Small Capacity UPS

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

Interesting thoughts - in most consumer devices, the temperature regulation is true. Heat's one of the worst enemies of 
laptop and cellphone batteries, after all. In house and datacenter environments for larger units, not really an issue. 

For operational spec for a lot of cells I'm used to, I'm used to 0 to 50c for design charge range for cells, and -20 to 
75 for optimal discharge range. Obviously, energy output (and energy to charge) differ across the range, but that's 
well within design specification for the rated lifespans of the cells. 

Long term storage, of course, is different, but that's a much easier solved problem, and design specs are often in the 
-30c to 25c range for optimal capacity retention over long term storage. But operationally, 25-50c is perfectly fine. 
Past ... above 5c, I think, you're looking at a 10% capacity fluctuation in that 5c to 50c range. 

Of course, there's a ton of other factors that go into such things as well, such as actual recovered (discharged) 
capacity such as current draw, and whatnot, other than temperature.

While true, heat is the enemy of lithium batteries of any type, deep discharging is the second worst enemy (BMS 
prevents actual cell damaging deep discharge, but you really should never go below 30% of rated capacity if you can 
ever help it - this is the most stressful zone), then charging too rapidly - too high rate of charge. 

As always though, it's best to look at the datasheets before making any decisions overall, of course. They'll cover all 
these operational specs and more. 

-----Original Message-----
From: Mark Tinka <mark@tinka.africa> 
Sent: Wednesday, April 9, 2025 8:05 AM
To: Gary Sparkes <gary () kisaracorporation com>; Vasilenko Eduard <vasilenko.eduard () huawei com>; North American 
Network Operators Group <nanog () lists nanog org>
Subject: Re: [NANOG] Re: Small Capacity UPS



On 4/9/25 13:49, Gary Sparkes wrote:

> An interesting thing to be concerned about, given average temperature exposures compared to consumer electronics 
> devices with usually inadequate cooling, compared to LiFePo4 in a UPS, which has been my baseline for years now as 
> SLA's age out.

It's often hard to keep Li-Ion batteries at the recommended 25°C. Some environments are worse than others, and while 
Li-Ion batteries can tolerate +/- 15°C, it's often not recommended. Some active cooling may be required for summer, or 
for perennially warmer regions.

Of course, you also have to think about extremely cool environments. 
Li-Ion batteries do not like to be charged below 0°C. In such cases, better to place a heater next to the battery so it 
can warm up before you start charging it. Charging it when it's that cold will lead to plating, which causes short 
circuits and capacity loss.

Mark.
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