Can I connect an uninterruptible power supply to a solar AGM battery bank?

[water2wine76]

My apologies if this is posted in the wrong forum. I'm looking to set up uninterruptible power to my amateur radio station for emergency communications. I have a small 12v diy solar system running into a 105 Ah AGM battery bank. With my current setup, in the event of a power outage, I have to manually disconnect my radio equipment from utility power and reconnect it to my battery bank. This could be a problem if I were in the middle of an emergency net. So I bought a used uninterruptible power supply from goodwill and as expected, the internal battery is no good. So I'm wondering, rather than replacing the UPS battery which is only a 2.3 Ah SLA battery, maybe It would be possible to wire the power supply to my AGM battery bank and that way I'd have 105 Ah capacity vs 2.3 Ah. Would this damage my battery bank since the UPS would be trying to charge the batteries without going through the charge controller? Is an SLA battery different from an AGM or are they the same thing? Is there a better solution that I'm not aware of? Any input would be greatly appreciated!

Thanks,
Jim

 

[timselectric]

I think that this should work fine.
But you should check the battery manufacturers recommended charging parameters to be sure.

 

[pollenface]

You can do it. My UPS supplies only 13.8/27.6v to the batteries so that's a very slow charging process.

 

[Hedges]

Many UPS came with Gel, so AGM might want somewhat different voltage or current.

 

[crossy]

Assuming you will continue to charge from your solar it should work.

You may want to disable (or make switchable) the internal charger in the UPS. You WILL want to disable the beeper

One thing to be aware of is cooling. Most low-cost UPSs are intended to run only for the time that the internal batteries will last and may overheat if run for longer periods. Additional heatsinks, ventilation, fans may be a wise addition.

 

[water2wine76]

Thank you to everyone who took the time to respond. I did some research and found out the OEM power supply battery (Vision CP1223) is an AGM battery. so I assume, it would be safe to allow the UPS to charge the battery bank. Initially I planned on continuing to charge from the solar panels but now that I know the UPS is designed to be used with an AGM battery, I'm thinking I might use the UPS as the primary charger and use the panels as backups in case of power failure. Is there any reason that I shouldn't do this? This would allow me to put my panels away in a safe location and maybe even pack my inverter and charge controller into a faraday cage. Thank you crossy for the heads up, i'm pretty sure I have a small cooling fan laying around that I can mount to the case.

 

[timselectric]

Thank you to everyone who took the time to respond. I did some research and found out the OEM power supply battery (Vision CP1223) is an AGM battery. so I assume, it would be safe to allow the UPS to charge the battery bank. Initially I planned on continuing to charge from the solar panels but now that I know the UPS is designed to be used with an AGM battery, I'm thinking I might use the UPS as the primary charger and use the panels as backups in case of power failure. Is there any reason that I shouldn't do this? This would allow me to put my panels away in a safe location and maybe even pack my inverter and charge controller into a faraday cage. Thank you crossy for the heads up, i'm pretty sure I have a small cooling fan laying around that I can mount to the case.

Compatibility was the only concern. Since you have figured that out, you are good to go.

 

[crossy]

I'm thinking I might use the UPS as the primary charger and use the panels as backups in case of power failure. Is there any reason that I shouldn't do this?

The only issue would be the built-in charger taking 1 million years to charge the big pack if it gets well discharged.

If you have a long power outage time to break out the solar panels.

 

[SamDeleted]

I use an APC UPS as my main inverter it works very well, no issues , apart from as @crossy said the beeper (now removed) and the tiny little useless built-in charger

 

[l00semarble]

Is your radio setup DC in the first place? Why not just run off the battery all the time and put a simple battery charger on the battery that will float it at required voltage while also effectively acting as a DC power supply for your system.

 

[water2wine76]

Thanks for the info everyone. I wasn't aware it would take a really long time to charge using the UPS. I don't know much about this sort of thing. That's not necessarily a deal breaker though. Most of the radios themselves are 12 DC and would run fine directly from the batteries, however they're all connected to source switches and powered speakers so that I can quickly switch between radios and monitor either through speakers or headphones, and those run on AC power.

 

[Jr233]

i have license also. i run just on battery hooked to your solar. that way you be off grid 100% and save some cost and not need the power supply. there is a device that. hers what a fellow ham who when APC was in Florida . the charging circuits
of the putty color metal case was very robust but the invers was the weak point. they had a very heavy transformer capable to keep larger batteries charged 100 ah drained still should be charged by a correct charger .they will keep batteries topped off the black flat units were built for 7 to 9 ah IMO a 35 i saw should be largest practical . you could easily rig a
switch or buy one to switch from power supply to battery and if at station you might lose a word or 2
73