UPS battery hookup

Virtually all are wired in series. The concept of more voltage and less current is more efficient. THat said, I use a 3500 KVA unit with ten 12V batteries in series for a 120 volt battery pack.

Generally yes it is OK. I've used some large batteries in UPS units to make a long lasting system. We're talking using huge batteries!

Yes, it probably would take longer to recharge them. Most UPS chargers don't have the balls to put out more than a small charge rate. Bigger, professional units usually run inverter 100% of the time (and so as a result you never miss even a part of a cycle on a power failure) but small, SOHO units such as yours don't. That's life, not worth worrying about.

DO it, and post the results.

Of course, if you can find a manual or some more information, that would be best, as advice such as mine may not be accurate--I don't have one like yours.

Thanks for your reply Peter. I agree with all your comments, and confirm my thinking about the batteries. I'll have to get a few heavy duty connectors and make the connections. I suspect that all will turn out fine. A bit messy because the bigger batteries will have to stay outside the UPS. Maybe a wooden box to hold everything, and a small fan to keep air circulating through it.

I'll report back in a few days when I have evaluated it.

When I did my oversized battery setup, I used a large plastic tray. You need something or the floor (or wherever you sit them) will be damaged most likely. (IIRC, I used the top of a plastic storage bin, it had a 1" lip, and was just the right size for two big (Car) sized batteries.

Use heavy gauge wire! (maybe a #6 AWG or even a #4) I recommend welding cable as it is flexible, and you can get color coded (red and black) if you want. Try eBay.

The correct wire for this UPS is AWG10. The pigtail I need to connect the batteries will only be around 12" max, so no need to get extravagantly oversize on the wire. And yes, I understand about putting the batteries in a plastic container; these are SLA batteries... not wet automotive batteries. I'll not pay the extravagant shipping charges that most Ebay sellers want, especially for a couple feet of wire. I'll go to Home Depot and get what I need, and for a much more reasonable price. The connectors are just 1/4" Faston quick-disconnect terminals.

I second the other responders; I have used 55AH batteries on my SmartUPS 1200 that ISTM, came with 4 or 6 AH ones. They both ran a long time and took even longer to recharge. But I hope yours are deep-cycle batteries.

Do note that many UPS's use the battery jumper for a fuse; it's the ideal place.

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Batteries are rarely wired in parellel, for what should be an obvious reason -- what happens if the voltage of one drops below the voltage of the other?

Where did you find 55AH batteries that would fit in a space that held 6AH units?

At that size, you fit it externally and use it as a pedestal for the UPS!

A piece of #4 gauge cable now exits the rear. It goes into ventilated area where an old cafeteria tray holds the batteries.

Nope; it's just fine. All it needs is patience. I had a 30 hour long power failure once. The batteries held out. I didn't care that it took all week to recharge them.

A lead-acid battery charger is a constant-voltage, current-limited, device. When presented with a undervoltage battery, it tries to charge it, up to its rated current. If it takes an hour, OK; if it takes a week, OK too.

At some point the leakage current would be higher than the max output current of the charger, but that's a LONG way to go... Maybe some of these will do the trick..

those

longer

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Therein lies the problem with that approach (which I also use) - the in-built charger is generally only sized to handle the original batteries, and may never actually be able to charge the upsized bank to a decent final terminal voltage. A separate charger is often required, and integrating that into the UPS system isn't always straightforward.