[NANOG] Re: Small Capacity UPS

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

Wanted to reply to this thread and add the pictures I couldn't send before,
but here is an example of what I am doing with APC UPSs I usually get for
free. People throw them out when the batteries die.

https://photos.app.goo.gl/xUiz28cDtwTygw2m9

With 2x 12 volt LiFePo4 batteries, you should have a balancer like the one
in the black 1500 UPS. I drilled a hole and used 3m double sided tape to
mount it. I like that I can see the voltage of each battery. All these
lithium based batteries have an internal BMS (battery management system)
but if you put 2 or more in series, you want a balancer as well so they
don't fall out of line. I still have an old UPS with 2 external AGM
batteries, I modified it to use the battery disconnect as the battery plug.
I use a balancer there as well. 7 years still working good for my needs.
When the batteries go, ill replace them with LifePo4. Pay attention to the
BMS specs on the batteries to make sure it is powerful enough for your use
case. So far I have not had any trouble with my upgrade to these old / free
UPSs. Anything I can use that doesn't end up in a landfill is good for our
children, and our children's children.







On Tue, Apr 8, 2025 at 2:29 PM Dylan Ambauen via NANOG <
nanog () lists nanog org> wrote:

> On Tue, Apr 8, 2025 at 6:06 AM Dave Phelps via NANOG <
> nanog () lists nanog org>
> wrote:
>
> > If you don't mind building you own UPS from COTS parts, you may want to
> > look at Xantrex (https://xantrex.com/). I have one of their UPS units
> (the
> > FREEDOM XC PRO 2000) in an RV with 2 100AH LiFePo4 batteries in parallel.
>
>
>
> Yes, an integrated (inverter + charger + power supply) connected to
> batteries is the simplest, most compact, plug and play.
> Another example product:
>
> https://www.aimscorp.net/product/2000-watt-pure-sine-inverter-charger-24-volt/
> Options exist to additionally combine solar MPPT inputs.
> Sealed Lead Acid AGM 12v 100Ah batteries still work, I don't rule them out.
>
> If you can avoid converting to AC, then you avoid the inefficiency of an
> inverter running with undersized loads. You need an integrated (charger +
> power supply), Iota is very good.
>
> https://www.iotaengineering.com/products/dls-power-converters-battery-chargers
> Call Iota and speak with an engineer to correctly size the
> charger/batteries and 12/24/48v, I learned a lot in 5 minutes.
> A power supply+charger can charge the battery all the way up, drop to a
> maintenance voltage, and still source all the current to feed your gear
> without overcharging the battery, similar to an alternator in a car. The
> power supply must have capacity to source enough current at maintenance
> voltage.
>
> A device like this can replace AC power supplies for ATX boards:
> https://www.mini-box.com/DC-DC
> Here is an excellent 1 port POE Injector with 12v UPS, connect a battery of
> your choice and enjoy: https://mikrotik.com/product/mups
> Consider using a battery balancer for arrays with many batteries.
> https://www.victronenergy.com/batteries/battery-balancer
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