[Sentoa] AGM Batteries

[Mark & Susan Perlick]

There are several advantages to AGM batteries besides the obvious ones of
not needing service and the ability to install them in any position.  In my
experience (I had Lifelines on my Island Packet sailboat) there were two
additional characteristics I really liked.

First, they will charge faster.  As wet cell batteries charge, the charge
acceptance rate diminishes.  So, if you are motoring short distances between
anchorages or running the genset to heat water and charge batteries, you get
more amp-hours back into the batteries in a given period of time.  AGMs
could be an alternative to increasing total battery capacity because you get
more amp-hours in so you can get more out for the same charge/discharge
cycles.

Second, those of us who must haul their boats for winter storage appreciate
the extremely low rate of self-discharge.  I forget the statistics, but wet
cell batteries, like golf cart batteries, loose as much as 10% of their
charge per month in storage while AGMs are closer to 1%.  This means not
needing to charge the batteries during winter storage to prevent freezing
(if you store unheated).  We'd haul our Island Packet in late October and
launch in April/May and start the engine with never having charged all
winter (outside storage in Michigan).

All that said, I'm using all wet cells on my tug since we do enough motoring
and genset operation that charging is not an issue AND we use heated
storage.  However, I sure go through a lot of distilled water and I hate
servicing the batteries--it's almost impossible to avoid some spitting and
spilling.

Mark Perlick
Steadfast NT37-050