Can I fit a bigger battery in my UPS?

February 12, 2008 9:35 AM

Can I fit a bigger battery in this UPS?

I got this ups from work, but the battery is dead.
It's a 12v, 7.2 Ah Lead-acid battery.
Can I use a bigger battery, custom-fit the wires to the big battery and have it work?
For example, this battery .
Thanks.

posted by PowerCat to technology (10 comments total)

maybe.
posted by zengargoyle at 9:57 AM on February 12, 2008

Here's a battery that a guy (in the comments) says he put in his APC UPS systems. That's one data point for you.
posted by Floydd at 9:58 AM on February 12, 2008

Your UPS is 6.5 x 3.6 x 11.2 inches. The battery you suggest has these dimensions: Length: 7.70" Width: 5.19" Height: 6.10". You can't fit that battery. You can't fit the battery Flyodd has linked to either.

The replacement battery for your UPS is 4.8cm x 10.2cm x 14cm (about 1.9" x 4" x 5.5"). Have a look inside your UPS and see if there is any spare space around the battery. If there isn't, then the biggest battery you can fit is one with those dimensions. Otherwise, measure the battery cavity.
posted by ssg at 10:35 AM on February 12, 2008

Wait, by bigger do you mean "more powerful?"
posted by rhizome at 10:45 AM on February 12, 2008

My question isn't about the size of the battery. It's about whether it'll work or not.

I don't have a problem with having the huge battery next to the UPS with wires sticking out.

By bigger, I mean physical size and more powerful.
posted by PowerCat at 10:52 AM on February 12, 2008

I've used a non-APC replacement battery in this very UPS, and it works fine, but the battery I chose was the Yuasa equivalent in dimensions and capacity.
I don't know if a bigger battery would work. Firstly, you want to avoid having long battery leads, and these things draw a fairly honking current, and long DC leads get hot. Secondly, you won't be able to draw more power by using a bigger battery, as the inverter has a definite (and quite small, in this unit) current limit. Thirdly, the charge controller may not be able to fully use the large battery, since the charge time might be hard-wired to prevent overcharging of the small OEM battery.
posted by scruss at 10:55 AM on February 12, 2008

What do mean by "more powerful"? Do you mean a higher power storage capacity, so that you can draw the same current for a longer period of time or do you mean a battery that can deliver more current?

BTW, you might want to read your question over before posting in the future because asking "Can I fit a bigger battery in my UPS?" is not actually the question you wanted to ask.
posted by ssg at 11:09 AM on February 12, 2008

Well, a lead-acid battery is a lead-acid battery is a lead-acid battery. They approximate voltage sources, so as long as the battery you use is of the same voltage as the original, it'll work... for varying values of work. There's absolutely nothing stopping you from using four 12V deep-cycle automotive/marine batteries in parallel.

The big question is whether or not the charging circuit has enough power to recharge the replacement battery/batteries. It takes a fair dinkum bit more power to charge a battery than the battery actually stores, so recharging to 100% after even a small outage could take a significant amount of time. Think of it like filling a bathtub versus filling a swimming pool - if all you have is a hose, it might be better to keep your emergency water in the bathtub... who knows when the next drought might hit?

Don't worry, by the way, about damaging the charging circuit - the replacement battery will have enough internal resistance to prevent that happening and the charging circuit approximates a current source.
posted by TheNewWazoo at 11:27 AM on February 12, 2008

YES. I do this all the time.

As I've stated here before, I like to cruise thrift shops, buy dead UPS's, and put bigger batteries in them than the manufacturer intended. In many cases a Dremel with a cutting wheel will come in extremely handy.

Notes: Don't touch metal contacts, even when the UPS isn't plugged in. It's designed to be live without external power. Be careful about polarity. Be careful about insulation. Be careful about ventilation (not all sealed lead acid batteries are ventless). Be careful that your new, improved design doesn't endanger a curious child. Please, please don't be stupid.

Oh, and have fun. This is a great, simple project that pays great dividends.
posted by SlyBevel at 1:33 PM on February 12, 2008

Yes, mostly. As long as the battery is the same voltage and type (agm or gel-cell).

As far as adding a battery to be able to support more of a load, no. That depends on the circuitry of the unit.

Adding a larger battery to give you a longer run time, yes, mostly. The only issue is that a unit not built for longer run times could overheat on an extended run. But this isn't too much of an issue.
posted by gjc at 2:25 PM on February 12, 2008