[NANOG] Re: Small Capacity UPS

[Javier J via NANOG <nanog () lists nanog org>]

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

[image: image.png]
And the batteries are way lighter.

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.

[image: solar-april-11.jpg]

As you can see, the voltage is stable and then jumps to 100% when fully
charged. I find that interesting.

On Fri, Apr 11, 2025 at 9:29 AM Mark Tinka <mark@tinka.africa> wrote:

> On 4/11/25 14:45, Javier J via NANOG wrote:
>
> This is why lifepo4 is a perfect swap in for old UPS devices like im doing.
> usually full charge is 14.6v is what the chargers my talentcell and solar
> charge controller cut off at, the batteries rest at about 13.5 full charge.
>
> Currently one of my UPS is floating at 13.7 each battery, another older UPS
> at 13.8.
>
> I've easily gotten more runtime out of these than what I have experienced
> with SLA or AGM batteries.
> my use case (home & home-office), keeping access points (4) internet,
> router, switches etc, even home theater (with the exception of the sub
> amps) up and running gives me like 2+ hours. Plenty of time to get the
> generator up and running. Last time we had an outage for an hour plus I
> wasn't even home. Didn't even notice it.
>
>
> Even if an LA and Li-Ion battery may have the same capacity, the operating
> assumption for an LA battery is that it will not be discharged below 50%.
> While you can discharge an LA battery below 50%, it will significantly
> reduce its lifespan, which is why they tend to be replaced every so often.
>
> In other words, Li-Ion batteries allow you to access nearly all of the
> battery's capacity without negatively impacting lifespan. This is the
> primary advantage Li-Ion has over LA.
>
> To get the same usable capacity from LA as you would Li-Ion, you'd have to
> double/triple/quadruple your battery size to gain usable capacity at a
> maximum DoD of 50%.
>
> Mark.
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