[NANOG] Re: Small Capacity UPS

[Mark Tinka via NANOG <nanog () lists nanog org>]

On 4/11/25 17:02, Javier J wrote:

> There is also the discharge curve, I think this is why my UPS upgrades 
> have been lasting way longer on battery:

Yes, Li-Ion's discharge profile is rather flat compared to LA which is 
more linear.

Li-Ion will hold a steady voltage throughout discharge, and sharply drop 
off as cell voltage gets into the region of 2.9V - 3.0V (LFP). The BMS 
will kick in somewhere between 2.5V - 2.8V to protect the battery from 
further discharge.


> And the batteries are way lighter.

Much higher energy density for Li-Ion than LA, which translates into a 
lot less floor space and weight for the same capacity.


> Here is output from my bluetooth solar project. you can see it maxes 
> out and then just maintains at somewhere in the 13.5 volts. 100% SOC area.

These are good values.

For 12V LFP batteries, I'll charge them to about 14.2V, and then let 
them float at 13.7V.

But 13.5V to float is great to increase battery life.

Mark.
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