In rec.crafts.metalworking Ignoramus7945 wrote:
I have a lot of things, most of which have batteries, and therefore I
have a lot of battery chargers.

My experience with them has been generally negative. The worst are the
so called "smart" chargers.

The problem is that they are often the opposite of "smart". They go
crazy and stop charging for no reason, or worse, drain the batteries.
Additionally, they fail due to things such as cold weather or
whatever, things any decently made item should handle.

The chargers, at least for lead acid batteries, would really be better
off, if they simply tried to maintain 13.3 volts or some such.

My question is, is my experience unique and atypical, or have you also
had bad experience with battery chargers.

It's pretty safe to say most chargers are just stupid, but lots of
batteries are also garbage, and neither can compensate for each other in
the end.

Apparently the last batteries installed in the UPS at work were total
pieces of garbage and are dying off before 5 years. They're larger than
car battery sized so should last quite some time.

The testing company comes in and does an ESR test on each battery, which
shows faults the charger (it's a 545 volt system) won't ever detect.

The charts for each battery are pretty cool, (sorry, I can't share them).
I can note that one problem battery is about 250mV lower than the rest and
has an ESR of 65,000 microhms vs an average of 15,000 for the rest. One
year ago the bad battery had voltage of 14.00 which is high, so the
failure wasn't sudden and the weird data shows up on various charts.

They've removed the funky battery from the battery string and then dropped
the charger voltage in the UPS to prevent damage to the rest of the
batteries.

Basically, if this battery which might explode under real use was attached
to a 12V float charger all that would happen is more electroylte would
just boil out, it would never finish charging and it wouldn't work right
anyways. The charger would have no idea anything was even wrong without
past performance data or known good specs for the battery being inputted
anyways.

Batteries are can have complex failure modes that you just won't catch
with a volt meter. It looks like full load on these batteries is about
150Amps, so it's any hot spots would get get really interesting buring a
power failure.