On Mar 12, 4:03*pm, Peter wrote:
Denny wrote

AGM is the best thing since sliced bread...
You do need to make sure the charge voltage is set properly for the
AGM (lower than for flooded cell)...

denny

I didn't know that. How much lower? Mine is 28.0V.

Well, my nominal 12V system is set at 13.4 V during flight/charging,
and my battery maintainer (not charger) puts out a regulated 12.6 V
(as measured on a Fluke meter) and my AGM battery is 3 years and still
acts like it is brand new... If you use a so called trickle charger,
check the trickle voltage, if it is more than 12.6 it will hurt the
battery in the long run...

In general, the AGM have thinner plates with closer spacing that do
not tolerate the high charging currents that a flooded cell will
take... Lowering the charging voltage lowers the charging current...
It simply means that it takes bit longer to recharge after starting,
etc... Not a big deal, and in return you get the much faster cranking
and no spilling of the AGM battery...
So, extrapolating for the charging voltage in flight, I would suggest
26.5 volts... And I would consider adding a charge maintainer for
sitting idle (stops the plates from sulfating) that puts out something
near 24.5 volts......

denny