GardenBanter.co.uk - battery voltage

rb wrote:
My battery at rest is showing 12.3vdc. Is it good or bad

Andy replies:
One can't tell from the info available.... I am assuming you are
talking about automotive-type lead acid batteries in the 12V
systems....

1) Has it been sitting for 5-6 hours since the last charge cycle ?
It takes
at least that much time for the "space" charge to dissipate for
an
idle battery.

2) Terminal voltage as an indication of "state of charge" is
temperature
dependent. 12.3 is a bit low, but it doesn't mean the batter
is "bad".
It may mean that the "state of charge" is low and recharging is
needed.

3) Your best test is to go and buy a specific gravity tester which
sells
for two or three bucks at an auto supply section. While SG is
also
temperature dependent, it is a much better indication of the
state
of charge. The instrument will have directions on how to
interpret
the results.....

4) Your best bet is to first measure and record the SG for each
cell, and then charge the battery at a low rate, say 3-4 amps,
for a day. Then disconnect the charger and measure the SG
again.
This will let you know if each cell can accept a charge, and
how
evenly they are charged..... In an automobile environment,
it's
usually the end cell closest to the engine block that goes
first.
I'm not sure why, but I've seen this a lot of times... Probly
heat....

5) Check the water level in the battery. If you have to top it up,
use
distilled water, and don't believe any SG readings for a while
since
the SG tester will pull the "uncharged" water off the top and
not be
an indication of the true state of charge until use/vibration/
gassing
has caused the water to fully mix with the electrolyte.....

Just a few tips.... If you google on "lead-acid battery
characteristics"
you can spend a few minutes learning a lot about how they should
be charged and measured.

Andy in Eureka, Texas