IF EVER THERE WAS AN AREA OF BOAT MAINTENANCE shrouded in mystery and old wives’ tales, it’s got to be how to properly care for marine batteries. Just talk to your dock mates about batteries, how to make them last, and what’s good or bad, and you’ll get five different opinions from five different people. Having just purchased a new pair of batteries for my own
boat, I’ve recently felt the financial pain associated with battery replacement.
So, maximizing what we refer to as “cycle life” – the number of times you can
discharge the battery to some specified level – is increasingly important to make
sure you’re getting your hard-earned money’s worth.
Each battery category has its place, and maximizing potential cycle life is in part dependent
upon what you need the battery to be able to do best.
DEEP-CYCLE BATTERIES are designed to provide a nearly continuous amount of current for an extended period of time and to be recharged many times over.
CRANKING BATTERIES are designed to provide a burst of high current (cranking amps)
for a very brief period of time, basically long enough to get your engine started. These batteries
are a poor choice for deep-cycle applications.
COMBINATION BATTERIES are simply a compromise category that provides adequate
cranking amperage to get engines started, yet can deliver moderate amounts of continuous
current for an extended period of time but not as long as a true deep-cycle battery. Each of
these can be made using differing battery technologies, which differ by how the electrolyte
LONG LIVE YOUR BATTERY
Smart tips for understanding your battery and maximizing its
cycle life – and your return on investment BY ED SHERMAN
Most cruiser-style boats will have a combination of cranking and deep-cycle batteries.
Often the deep-cycle battery bank will be
made up of multiple batteries to supply
power for extended periods away from the
dock, but the boat may have only one dedicated cranking battery to get the engine started. Another common configuration today is
to use deep-cycle batteries for everything on
modern cruisers. This approach can work
fine as long as the CCA (cold cranking amps
at 0 degrees) or MCA (marine cranking amps
at 32 degrees) rating for the battery matches
the requirements of the engine. This is easily
accomplished today because modern starter
motors draw far less electrical current than
their historic counterparts. For my own boat,
which is a center console that we use extensively for fishing, we use a pair of combination or dual-purpose batteries that work just
fine for frequent starting and shutting down
as we move from one hot spot to another,
and for the occasional anchored-in-place
application with the stereo, instruments, and
lighting drawing power.
To understand the important maintenance
procedures required to maximize cycle life,
there are a few terms you need to be clear on:
electrolyte, sulfation, and equalization.
Electrolyte is the solution through which
the ions move that give the battery its electrical potential. Depending on the specific
battery technology you use – flooded cell
(either sealed or not sealed), absorbed glass
mat (AGM), or gel cell – the electrolyte
will be in a liquid format or immobilized. For
lead-acid batteries, we’re
talking about a mix of
distilled water and sulfuric acid. AGM batteries have the liquid saturated into matting that
is squeezed between the
plates inside each cell of
the battery, effectively
immobilizing the electrolyte. Gel batteries use
a mix of sulfuric acid,
water, and a thick silica
gel to immobilize the
PRACTICAL BOATER | MAINTENANCE
50 percent can
shorten its life.
Be conservative. Size your
house bank to
at least twice