Rework a UPS with Massive Capacity

Step 4 Use it

That's pretty much it. Simple, right? The hard part is finding the right parts and connecting everything in the right order without welding anything.

You should now be able to plug in the UPS and go.

Some additional thoughts and enhancements:

1. You are using lead-acid batteries. In the photo, I've shown a plastic layer under the batteries. Even though marine batteries are typically sealed, you do not want to take the chance of a leak. Spend $8 - $20 and get a plastic battery box for each battery you use. It will protect the batteries ... and your floor.

2. In the first step I claimed this would improve the capacity, massively. By how much you ask? The largest gel cells I've found in UPSs are 20AH. Others are more like 7 AH. Using an 85 AH marine battery to replace a 20 AH gel cell, you should expect to get at least four times the runtime. HOWEVER, do not plan to run the batteries down by more than 50% or you will severely shorten their life. Figure more than a doubling of capacity, but less than 4 times. If you use a 115 AH battery, figure at least 3 times the run time and a much longer battery life.

3. I have not had any problems with the UPSs recognizing the new batteries or keeping them charged. If you have the UPS monitoring software, use it and try some tests. See how long your new rig will run before hitting the 50% charge level.

Expect the total cost to be about $80 for a single battery setup with 85 AH battery and battery case. Double battery setup with 115 AH batteries should be about $160, max. These are using battery prices in summer 2009. Battery prices spiked briefly last year, but have come back down.

Comments

[hmv4u]

did this with my Smart UPS by drilling two holes in the case and threading cable to two x 38ah batteries- run it as a supply/backup for a heater and pump in my marine fish tank,has run for two years without any problems-id agree with the overloading but in reality would people run full load ?

[Forcelord50]

With a nice new Core i7, SLI graphics cards, and a dual monitor setup for a computer system, yup some people would.

[bben46]

Nice Instructable. However, I would recommend a fuse between the batteries and the UPS. It might prevent a fire.

[Winphreak]

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?

[frollard]

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.

[Winphreak]

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.

[Surferdude]

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.

[Winphreak]

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.

[frollard]

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

[Atown93]

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.

[ben.mcfadden]

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]

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.

[adamvan2000]

Problem: too much heat, small heatsink Solution: biiiiig heatsink, active cooling system(fan in case, mebbe two) ???? ~adamvan2000