On 5/12/2016 9:01 PM, HerHusband wrote:
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.

That's true of most UPS's in the 600-1500VA capacity. At lower
capacities, the cost of the second battery tends to drive a lower
(DC) voltage design -- higher relative switching losses. Batteries
are mounted side-to-side or top-to-top and held together with
(effectively) "thick tape".

There's usually very little "extra" room in the battery compartment so
a UPS that cooks its batteries can leave you with a mess -- trying
to pull a "swollen" battery out of an already tight spot.

The larger capacity (2000+ VA) units tend to move up to 48V packs
for increased efficiency. And, the packs tend to be genuine entities
(not just batteries taped together but actual "enclosed cartridges")
Part of this is due to the increased weight of a set of four, LARGER
batteries as a replaceable unit.

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.

IME, the UPS is the bigger problem than the batteries. I.e., you can
easily change battery supplier (screw me once, shame on you; screw
me twice, shame on me!). But, a misbehaving UPS will eat good batteries
just as happily as bad batteries!

APC UPS's tend to overcharge their batteries. What's worse is the
charging circuit seems to degrade over time. So, a UPS that is
targeting an "ideal" cell float voltage can slowly creep up to
an unhealthy level... and this isn't noticed until your "battery"
is toast!

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.

A better solution is a better charger. You'll note that the
batteries in electric vehicles aren't naively charged (based solely
on their two endpoints!). But, this adds to the cost of the UPS
and requires changes to the batteries chosen. I.e., you'd want
access to individual cells (or pairs of cells) instead of
"groups of 6 cells". This would also cut maintenance costs as
you could detect and replace bad cells instead of losing a set
of 6 due to one of those 6 failing (and cooking the others).