APC uses 2 basic batteries in the half dozen or so units I have here.
In some units they just glue a couple together to create a "battery
pack" that they charge handsomely for, I suppose people who can't read
specs and do a little shopping appreciate the simplicity so APC does
it. There are plenty of customers who just throw the UPS away when the
battery is dead.
These are industry standard parts and I want to get them at the best
available price. I certainly have not noticed that much difference
between the life of a APC sourced part and one I get from a battery
wholesaler. The wholesaler actually tends to have fresher ones.

My Cyberpower UPS has two batteries assembled into a single unit. Remove
the cover, slide out the old battery unit, slide in the new one, replace
the cover.

I made the mistake of buying inexpensive aftermarket batteries a couple
years ago. The UPS claimed it would run over 70 minutes on the batteries,
but when the power went out I was lucky to get 5 minutes from them (after
three days of charging). They drained way too fast.

I recently bought the "genuine" Cyberpower batteries and now I really do
get more than 70 minutes when the power goes out.

I'm sure the first set were just low quality as I've purchased many
aftermarket batteries over the years. As you said, they're usually better
than the official batteries.

Anthony Watson
www.watsondiy.com
www.mountainsoftware.com