"Harry Krause" wrote in message
. ..
Mr Wizzard wrote:
Optima's are bad news. Really they are...
All AGM's are vibration sensitive, but some
are better than others. Best one on the Market
are made by Hawker, but they are commercial,
and for Telco etc., so I don't know if they are
easily available to the public, but might look
aroun on-line. Why AGM? What need do
you have that warrants AGM?



I've been running boat electrics off Optimas for years, and have not had
any problems, nor have I encountered another boater with Optimas who has
had problems. So, why "bad news"?

I've seen multiple Optimas develop internal shorts inside of a year, some of
which were covered under pro-rated warranty, many which were not. The
way to detect this with an Optima is to check the final float currect at
13.8
volts. On a failing (or failed) unit, you will see that it never achieves
final
"finishing charge" - that is to say that it will float down to about 400ma,
(at 13.8 - 14.0 volts) and sit there at ~300-500ma forever (indicating an
internal short, or bridging, or leakage in the G.M). Remember, in a G.M.
setup, there is no provision for bridging/shorting particles to fall out of
the
way like you have in a flooded cell. If you keep the thing charged all the
time, and only using it for light current draw electronics, you "may" be
ok, but if you need full capacity, or "usable" capacity after sitting for a
while, you may be in trouble one day. Rememner, leakage draws that
few hundred milliamps ALL the time: during charge, discharge, and when
just sitting. A healthy AGM in the size we're talking about should draw
between 40ma - 175ma at final float finishing charge at 13.8 - 14.2 Volts.
Maybe you were lucky to get good Optima's. Good news is thast they
are cheap, right? So anyways, thats the "bad" news I speak of. My
general rule of thumb is, unless you have a specific reason to warrant
a AGM arrangement, don't do it.