Instructables
Picture of Rework a UPS with Massive Capacity
Those UPS devices you buy for your computer usually have a gel-cell battery that lasts for a few years. Less if your power goes out a lot. When you replace them, you pay a bundle, even if it's a standard cell. This short Instructable will demonstrate how to rework an older UPS for more capacity with cheaper battery power.

The picture shows some sample UPSs and an example of the gel cell from one of them. The UPSs come in various capacities and, although you can boost the capacity, the output power is fixed. When you start out, make sure that the UPS you're going to modify will provide the volt-amps and power that you need. Also note that the volt-amp rating is higher than the power rating. The difference is because AC powered devices have a power factor. Check online for more info about this. Another, similar Instructable, also warns against trying to max out the capacity of your UPS because some use transformers that will run continuously at the rated output. It really depends upon the quality of the UPS, but plan to run at not more than about 75% of rated output capacity.

Another thing to consider is whether or not your scrap UPS has AVR or Automatic Voltage Regulation. You'll want this if you can find it.

 
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ronemshoff6 months ago

I have two near new 1000VA/600Watt UPS, each containing one 12 volt battery. Each will run a computer for about 15 minutes on battery. I have completed the conversion to 12 volt marine 100 amp hour battery on each. They both work as planned when plugged into main electric supply. However when unplugged from mains they will carry only a small load such as small light or fan, but the minute i add a computer the fuse blows. Conclusion, the computer is too much load for the unit when combined with the 100 amp/hr battery. Can someone offer a solution.

Surferdude (author)  ronemshoff6 months ago

Two things I can think of to check. The first is to try unplugging the UPS from the wall outlet while the computer is running on the outlets supplied with battery power. That best simulates what happens when the power goes out. Some UPSs get wonky if you change the load after the power goes out. The second is to check the fuse rating. For reference, the input current rating on the CyberPower 900AVR in the photo is 12A. A 600W UPS should have at least a 5A fuse, and that would very likely blow every time you turn something on, just because of the surge current. You should either have a fuse that is equal to or slightly higher than the input current rating, or a slow-blow fuse that can tolerate surge currents.

Is this fuse that's blowing on the outputs from the UPS or on the input from the A/C line? The input fuse has to be able to handle both the full output of the UPS as well as the charging current required to simultaneously charge the battery and run whatever is plugged into the unit.

One more thing: Recheck your wiring to make sure that something didn't actually get shorted. No wires touching bare metal anywhere, no screws that dropped inside the device, etc.

Thnx Surfer for your help. I added a 15A fuse inbetween the posivite side of the new 100A battery to the UPS as a safety precaution. That is the fuse that keeps blowing. It is not a slow fuse. Soon i will add a 30A here, and if that blows, a 40A. couldnt find a 50A without going to a very large and expensive fuse holder. I will also add a surge arester. And because you are interested i will report back. Maybe it will help some other poor slob. And if all that fails i give up.
thnx so much for quick response.
o.k. here is how I have this wired - pos to pos, neg to neg, just take out the old small battery and insert the large new battery. just like this and several similar web sites - all say much the same. no shorting, plastic housing, no wires touching, and good 10 gauge wire with crimp connecters from unit to battery. I noted the unit also charges nicely, as when i got the new battery it read 12V, but after charging for 24hr, now ready 13.2V and charger light changed from blinking to solid on meaning fully charged. the only thing I am doing different is I inserted an in line automotive type fuse of 20 amps. this is the fuse that keeps blowing. there is also a 5 amp fuse in the unit, but that doesn't blow. So again I tested, with the unit plugged into mains it will carry anything. then I have a small light and small fan running, unplugged from mains, beeps as normal, fan and light stay on, and fuse remains intact. then I unplug light, fan, and plug in computer (no monitor even) unit runs find plugged into mains, but the minute I unplug from main, the 20 amp fuse blows. maybe it is all the 20 amp fuse I inserted. I guess I can take the in line fuse out. comments please??? thnx again Ron

12v * 20a = 240 watts. Doesn't seem surprising your fuse is blowing running a computer. I assume the 5a fuse mentioned before is for the 120v AC power to the unit rather than the 12v from the stock battery. 120v * 5a = 600 watts. You need a 50 amp fuse on your 12v wiring to support your 600 watt rating. 10 gauge wire looks good for that.

CatMan31107 months ago

I have an old Avaya industrial charger I picked up a while back. It's rated at 10000VA, 8.3 amps 50/60 Hz output. What sort of baterry can I use this? Can I use the old battery from my truck?

Surferdude (author)  CatMan31107 months ago

That comment should actually go here:

No idea. Is it's a charger, then it likely converts AC to DC, which is not what a UPS / AVR does. The UPS combines a filter, charger, and inverter in one small box. If there's no inverter in your device, sticking a battery in it is not going to do you much good. Do you have a link to a web page for it?

IT's an UPS, dont know why I called it a charger, must be I was thinking of terms of the battery I want to connect to it. As far as a link for the device's web page, I haven't found one yet. It seems the UPS is too outdated to still be included on the manufacturer's website.
joepe9 months ago
If the batteries are hooked up as shown, they will be in series and will be 24 volts. That would be fine if your UPS had two 12 volt batteries. However, if the ups you are using had only a single 12 volt battery, but you wanted to extend the capacity by using two AGM deep cycles, wouldn't you hook the repalcements up in parrallel?
Surferdude (author)  joepe9 months ago

The number of batteries is addressed in Step 1, but it's good to reiterate the need to match the original battery configuration in terms of voltage. In this Instructable, the goal is to simply increase the AH capacity by using larger batteries. You could use multiple batteries in parallel at the required voltage, but then you run into battery balancing and overcharging issues.

biglovesam1 year ago
Got a question,I have a apc 550va, Will this work? Tapping the stock 12 volt battery terminals and connecting to my vehicles 12 volt system? I would disconnect while starting the vehicle, just want to know if the alternator would have any bad effect on the ups?
I recently built a ups from scratch. I built the switchover circuit and inverter. It converts the ac to 12v dc, which is used to charge the battery and power an inverter. When power goes out, the batter is switched in place of the dc power supply to power the inverter.
Do you have a website on building your own UPS, or how you did it? Might want to post an 'ible yourself...
I don't have a website for it, I didn't document it very well. Maybe someday, right now I'm just trying to learn and spending less time on projects.
advante3 years ago
Just by adding more battery.
Winphreak5 years ago
If the batteries sink below that charge level, wouldn't it be better to pull them out (if set up that way) and charge them with a standard battery charger, instead of trying to use the float charger in the UPS?
Assuming your power outages are far enough apart, the float charger is perfectly safe - besides, trickle charging a car battery is WAY better for it than quick charging with high amperage.
Thanks. I just figured that tricklecharging a battery with that much current wouldn't work. But, then again, it's not about amps, it's about volts. Just debating it practically versus what I learned about electrochemistry. I'll find out when I give this a shot this weekend. Thanks for the info.
It's guaranteed! Only trouble is as mentioned on this and another ible - the INVERTER probably doesn't have sufficient cooling to keep it running longer than the stock battery would allow - its only designed for a duty cycle that the battery could possible put out - usually less than an hour. :D
I have done a similar mod to a UPS that I had. I used the guts of a Forza 700va UPS and purchased 2 additional batteries, that were the same rating as the original, at the local hardware store.

I found the duty cycle and heat buildup of the transformer to be only the first problem. The larger problem was the software/firmware that drives the unit only allowed a duty cycle of 25 minutes. Even under load testing at 60% I was only able to get the unit to about 75% charge before the software would shut the unit down. After cracking the software and pasting several old CPU heat sinks to the transformer, its been running for almost 4 years now.

For cooling I mounted all the batteries, motherboard and transformer in an old micro tower case I had lying around. Even mounted the plug cluster exactly where the power supply would have gone (fit perfect). The unit now looks like a regular PC with the exception of some old school analog input and output voltage gauges and a charge gauge mounted where the CD drives would be. Even the HD and power LED’s work as they did on the original UPS..

The case gives plenty of air for cooling with the addition of a few vent slots cut in the top and bottom to allow the hot air out the top.

I'm planning to build another one for a neighbor who saw mine. I'm new to instructables but I’ll take plenty of photos of the build and post it.
The other ible you mentioned, just for reference to people (it just so happens to be my instructable:
http://www.instructables.com/id/Make_your_computer_UPS_last_for_hours_instead_of_m/
IanR frollard5 years ago
I would definitely agree with frollard about cooling. These newer (cheaper) UPSs have very small heat sinks as well as low duty cycle transformers. The older UPS units tended to be built a little heavier. Most of the new, light duty UPS units have plastic cases too so it could be a fire hazard if you ran them too long and they overheated. Not wanting to sound like a mother hen but, it's just something to keep in mind.
Problem: too much heat, small heatsink Solution: biiiiig heatsink, active cooling system(fan in case, mebbe two) ???? ~adamvan2000
Surferdude (author)  Winphreak5 years ago
Hey, let me know how it works for you! Also would be cool for people to post their experiences with different brands and any heating issues as described in that other In-able. I have not done any extensive testing with the two I made. I run the computer off one large 900VA unit and the displays and other stuff off a 500VA one. When I first made them I ran them down to about 50% just to see how the software monitor would react. At first it didn't seem to track % battery and time to empty, but then it seemed to adjust.
I was hoping to have good news... but it looks like one of the transformers went with the battery in my UPS. I get the feeling 300ohms in a 32V 40A transformer is not right. But, I'll keep this in mind for the next one I buy.
DO NOT do this to those baby UPSes. If you run a high power device (ie computer) off of battery power, it WILL overheat the inverter. Those small UPSes are only meant to run for a few minutes. Take a look at the heatsinks on the VRMs in there, they can't dissipate the heat fast enough. Get a UPS at least in the 800VA area to do this mod.

Here's someone that did it, and it overheated.
http://www.instructables.com/id/SYB2G6JFMZAFYV2/

Here's 2 more builds that mentions overheating
http://www.techspot.com/blog/137/turn-a-small-home-ups-into-a-giant-ups-diy/
http://old.drcheap.com/home/hoh/upsbattery/

There's another build thread that showed a melted UPS after connecting a car battery to it, but I can't find it anymore.

Here's a proper build with a large UPS.
http://www.ocforums.com/showthread.php?t=584475
I wanted to add a little on to my original post. The problem isn't replacing the batteries, its adding too high capacity batteries on a UPS that can't handle the power. Any UPS in a surge protector form is ill-equipped to handle a couple car batteries. Not to mention the fact the larger units have better power filtering, like over and under voltage correction, and true sign wave output. The only thing those small units are good for is running a cable/dsl modem, a consumer router, and maybe an additional network switch. I would never put a computer on one of those. The 1250VA unit I'm using right now has a transformer that probably weights more than the OP's surge protector sized UPS and stock batteries.
First, you're right, but it's "sine wave". Second, I do not approve of using those really low-power pseudo-UPSes for this purpose either. But I think that the addition of a bigger heatsink (in place of the batteries for example) or a fan would mitigate the risk of overheating.
Oops typo on the sine wave... I don't think its worth the effort in upgrading the heatsinks. Most likely you're gonna have to desolder the VRMs and extend them to attach to a larger heatsink. Also, the transformer is half of the overheating problem, and it just comes down to their build quality. They are small, cheap, and just ain't built for long runtimes. I think a fan should work, like you mentioned.

People just gotta start on a good platform, no point upgrading a crap UPS. The 1250VA unit I'm using now was free. Just check out garage sales, craigslist, and localy on ebay. If you work in a large office, talk to someone in IT, they normally pay companys to dispose of this type of equipment.
You're right, those crappy ones are hardly worth the effort. But maybe the entry-level ones (those 3-400VA models) would be able to handle the increased capacity (provided that you won't run an oven or a heater off of it). You must've been really lucky on that 1250VA model as you can hardly get them even in retail stores.
As for the suggestions, yeah, all of them sound good. Except.....well, there are no garage sales over here at all (it seems to be pretty much a US custom). Also I can pretty much forget about craigslist and eBay as well (no category for my locale/no eBay in my country). The only place I can think of for research are the junkyards and battery/IT equipment recycling facilities. I'll check out the former, but have no idea where to find the latter (I've been working in a large office, unfortunately they've managed to kick me out rather quickly so it's out of the question for now). Thanks for the advices anyway :P
Where are you?  I am in Brisbane and have found heaps of old UPSs on ebay etc.  Plus when I bought a big Battery I found out it came from a place that strips old offices and pulls apart all the equipment.  Good  luck!
Yeah, good for you. But as I said there's no eBay for me. As for the second source I don't have the slightest idea where could I find a company like that. My locale is Bratislava, right in the middle of Europe (or rather its eastern part....), that doesn't help things either. :P But as I said, I'll keep looking.
Isn't that where vampires come from?  Or werewolves :-)  Yeah I had never heard of recycling this stuff until I stumbled across them.  While I don't own shares in ebay, I know you can open accounts from OS and get stuff shipped to you , depending on freight and exchanges rates.  It can work out for books etc but batteries obviously suck for weight though.  Cheers
Well, I don't know about werewolves, but no, vampires aren't from Slovakia (which Bratislava is capital of), but from Transylvania, which is prt of Romania. You weren't that much off BTW, because both were in the same country ~100 years ago (before the end of WWI, to be more precise) :P
In the EU we have some laws making recycling of such stuff mandatory. This is why I figured I could find such company. And yes, I could use some foreign e-Bays as well (PayPal doesn't try to make your life miserable anymore when you're trying to use it from Central/Eastern Europe like they used to), but I think the postage would be way more than the price of the thing itself (especially if the seller would include the -possibly defective- battery as well). Basically this is why I prefer a local "supplier". I've ordered quite a few other things from such sites though (books, Arduino etc.), but there's also another problem. You see it's been a custom of sorts for companies in Yankeeland to ship only within the continent (many times they don't ship even to HI, AK or outside territories). They aren't the only ones to do this on eBay though, but the US companies seem to do it with e-shops as well. I could circumvent this limitation per se but it wouldn't be feasible for small amount of goods. So my options are pretty much limited. Still, this issue isn't that pressing for me. Thanks for the tips though.
Hey no problem... Its ironic that you are much closer to the US than me but getting stuff is harder!
Yeah. It has more to do with communist rule in the past (up to 1989) than with distance though.
Good warning! It'd be a good idea to monitor these things after you build and see what the safety margin is, then program your UPS software to shutdown way before then.
You are right there, I cooked mine last year on a utility battery twice the size of a car batter, I only ran it for 3 times longer than it lasted with the original battery and it went up in smoke. The heat builds up in the middle of the transformer and burns the coating off the windings causing a short, and it billows smoke until it trashes the drivers and blows the fuses. I HAD a Belkin.
laptopdude4 years ago
I have that apc ups but mine is 257 watts.I love upses.
hogey744 years ago
Man I love the web.... I had decided to do this recently as I have a big 100 amp hour battery for camping and I am looking around for a decent shagged UPS and then found this site accidentally while looking at Ikea furniture!  I love that other people have come up with the same ideas as me!  Even if they got there before me :-) 

My understanding from my research so far is that even most sealed batteries are valve regulated thus allowing a little gas to vent.  This is only if you over-charge however and I think UPSs should be pretty good at avoiding this.  I will make or modify a box for my rig, ventilate it well and I will place it in a big airy part of the house.  I found heaps of info from battery university - google it.  Also, I think you should avoid calcium infused lead acid batteries because when at 100% they typically sit at a higher voltage than non-calcium which means that the chargers in UPSs may not charge them fully.
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