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Re-purposed UPS as Inverter

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Dacflyer

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Jun 5, 2020
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Has anyone here ever re-purposed any UPS's for use as an Inverter ?
I acquired long time ago a new, never used APC 1400 rack mount 24v. it's good for 950W
I like that it can be cold started with out any AC input. I'm using it in one of my small solar projects.
I'm using 3 of the 295 watt panels i got earlier ( Canadian Solar ) and 4 100Ah batteries in a 2s2p configuration ( 24v 200Ah )
I got a good deal on a MPPT charge controller , it's good for 50A.
I got lucky and scored 2 free cabinets. one is a small truck box, the other is a NEMA3 DOT cabinet.
I'll share pictures later on.
I had to disable the beeper in the inverter, and the battery gauge it way out of calibration.
It started off full, but after about an hour the battery gauge showed the pack was flat, but the voltage on the controller showed 28.5v
So the inverter battery level meter is not used to a 200Ah battery....lol ( it is supposed to have 4 7AH batteries..) 24v 14Ah.

I wonder if there is a way to re-prorgram the meter on UPS and silence the beeper.
So far things are working ok,, I only have a light load on it right now.. will add more things later on.
Actually have Another UPS plugged into it, and my TV and DVR. 8 Cameras, the UPS seems very happy, it hasn't acted up a bit.
I thought they might not like each other, but it's doing good.
 
Yes, it has been done a few times by others on the forum. Check the maximum run time for the UPS if you plan on going down that path. It may not be rated for full time inverter operation.
 
Only issue with them is the huge standby watts they consume, around 140 often.
I have a ton of them I tinker with.
I've even got a huge 5KW unit... beast for sure.
 
Dacflyer said:
It started off full, but after about an hour the battery gauge showed the pack was flat, but the voltage on the controller showed 28.5v
So the inverter battery level meter is not used to a 200Ah battery....lol ( it is supposed to have 4 7AH batteries..) 24v 14Ah.
Click to expand...
The only thing to be careful about is if you are using Lithium batteries, This is that most UPSs assume Lead Acid and like to trickle charging your Lithium batteries at a voltage per cell that may shorten their life. 3.4 volts per cell would not likely be a problem. I could not tell from your post what your battery chemistry was.
 
Ampster >> there's no way the inverter can charge the batteries.. they only get charged thru the solar charge controller. and i'm using AGM batteries.

Supervstech >> you mean 140W just Idling ? that kinda sux..
I'll find something better later on i guess. but this is good enough for now..
 
I was thinking about putting LiFePO4s in one of mine, but the discharge rate for the given volume space wasn't sufficient.
 
gnubie >> will see how it does...it'll be 24hr use, unless i shut it down..
 
Not ALL have huge idle draw, but several do.
Most are from 55W, to some over 250W...
 
Ampster said:
Are you using them with Lithium batteries. Is trickle or float charge an issue?
Click to expand...
I don’t have them plugged in.
I use them strictly as inverters, charged by a charge controller.
But, yes, I use them with lithium batteries.
I have a LiNiCo, set I use, and a few LFP banks that run the boxes.
 
I been using this inverter for a while now, it seems to be doing a good job, i added in an extra fan to help keep the transformer cool,,
It's doing well.. The only thing i noticed is that in my bedroom, i have halogen lights on my ceiling fan. The lights ever so slightly go bright / dim. It doesn't happen to any other lights in the house..
All others are either led or fluorescent.
I'm curious if anyone else has such an issue with something like this using a UPS as an inverter
The voltage doesn't fluctuate on my DVM
I can't post a video of it..
 
Dacflyer said:
I been using this inverter for a while now, it seems to be doing a good job, i added in an extra fan to help keep the transformer cool,,
It's doing well.. The only thing i noticed is that in my bedroom, i have halogen lights on my ceiling fan. The lights ever so slightly go bright / dim. It doesn't happen to any other lights in the house..
All others are either led or fluorescent.
I'm curious if anyone else has such an issue with something like this using a UPS as an inverter
The voltage doesn't fluctuate on my DVM
I can't post a video of it..
Click to expand...
Odd.
Halogen bulbs are high wattage, so perhaps there is a output voltage fluctuation on your inverter.
what is the total load on it?
 
900W is the max load, but the light itself is only 3x 35W Halogens @ 120v
and it does not matter the load... it'll do it with a light load or heavy load.
it's defiantly a tiny fluctuation, I use an analog meter, and it's about a half of a volt or so.
it's not really a problem, just something i was curious about. It only seems to effect incandescent lamps or halogen.
I do not notice it with led or fluorescent lamps
 
Supervstech said:
I don’t have them plugged in.
I use them strictly as inverters, charged by a charge controller.
But, yes, I use them with lithium batteries.
I have a LiNiCo, set I use, and a few LFP banks that run the boxes.
Click to expand...
@Supervstech @Dacflyer
Any pictures of your setup ?
Curious about cabling, fusing, isolation switches (if any), etc

I also want to re-purpose an APC UPS as inverter only (AC power cord not plugged in, no battery charging from UPS, charging from SSC only)
No issues with having the SCC plugged into the LiFePO4 battery & UPS inverter/battery connection at the same time ?
Or should I use a Blue Sea Battery Switch (1 - SCC, 2 - UPS inverter/battery connection)
I have a PV breaker before the SCC (so it can be disconnected when switch at position 2)

BLUE-SEA-Battery-Switch-M-SERIES-BSS6007.jpg
 
Last edited:
I dont have them in permanent use.
I pull them out when power is out.
I just have the cells charged ready for use.
 
perpetual said:
@Supervstech @Dacflyer
Any pictures of your setup ?
Curious about cabling, fusing, isolation switches (if any), etc

I also want to re-purpose an APC UPS as inverter only (AC power cord not plugged in, no battery charging from UPS, charging from SSC only)
No issues with having the SCC plugged into the LiFePO4 battery & UPS inverter/battery connection at the same time ?
Or should I use a Blue Sea Battery Switch (1 - SCC, 2 - UPS inverter/battery connection)
I have a PV breaker before the SCC (so it can be disconnected when switch at position 2)

View attachment 49679
Click to expand...


Hi, sorry for the long delay.. I didn't get a notification.. I can post pictures soon, I'll have to take some.
I have everything mounted into a weatherproof cabinet. the UPS and charge controller are all in the box.
I have everything fused. I am not using any battery switches, Just a battery buss bar.
I do not know what SSC is...or maybe i'm too tired to think.. Solid state charger ? I'm going to guess that..
If i need a charge, in the winter when there's less sun sometimes.. I have my charger directly connected to the battery bank,
no worries of back feeding into the solar controller, it's no issue. and the UPS doesn't mind either.
The UPS battery meter doesn't like a big battery..it's not accurate at all, because it's looking at run time, not battery voltage.
so the meter shows empty all the time...lol
I have a separate volt meter for this..
If i do not post pictures in a few days, please remind me..
 
I have a UPS fetish with four different systems, three are APC. Show & Tell. This is what I’ve learned so far:
  1. Only the APC “XL” models are rated for continuous operation. You can easily identify by the rear external battery connector.
  2. Most other consumer UPS’s are designed to overheat shortly after the internal batteries are depleted. Running the non-XL UPS at minimal power, or adding fans to get around the heat issue won’t work. As stated above, the UPS will still shutdown based on a timer.
  3. The XL will automatically recalculate expanded battery capacity when using AGM. I have no experience (yet) powering with LiPo.
  4. The APC battery display is expecting a normal AGM voltage range. If you connect to solar, the higher battery voltage will manifest as one blinking bar. It's not indicating low battery. Show & Tell.
  5. Higher battery voltage can affect the APC capacitors (the little ones, not the big H-bridge ones). This affected my 2700W unit that will no longer boot. My to-do list is to replace them and see if it works.
  6. If you want a reliable pure-sine, low-frequency inverter a used UPS is your cheapest method.
 
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