maximum cycle life. With modern AGM and
thin plate pure lead (TPPL) batteries (TPPL
batteries are versions of AGM batteries), vendors will throw out numbers like 60 percent
to 80 percent of discharge as being totally
acceptable. This increases the amp hours
you can actually get from a given battery by
as much as 30 percent. That’s an important
consideration because of the limited amount
of space on board to store batteries. Weight
is also a factor; the idea here is more amp
hours per pound.
One of the most important things you
can do to maximize battery life is to install
adequate capacity to meet your needs, without exceeding the optimal discharge level of
If you’re using flooded-cell batteries with
removable cell caps, check the electrolyte
level monthly, and top up the batteries with
distilled water as needed. On any battery,
make sure cable connections are tight and
clean and free of corrosion. Once cleaned, a
coating of corrosion inhibitor like Boeshield
T- 9 is a big help. This bit of maintenance
ensures that you’ll get the most amp hours
out of the battery for powering up your boat,
and that the most amp hours will get back
into the battery when connected to a charger.
Once all the above has been accom-
plished, the bottom line for extending battery
life boils down to proper battery-charging
regimens tailored to the battery type and size.
The last 10 years have seen marine battery-
charger technology improve dramatically.
State-of-the-art units can be programmed for
up to three different onboard battery types,
and some provide an intermediate fourth
phase (most have three) of charging called
“pre-float” to better transition the battery
from what’s called the absorption phase to
the float phase, to maintain a 100-percent
charge level while automatically adjusting
voltage to ensure no overcharging. A good
one will come with a temperature sensor
for mounting on the battery for a more pre-
cisely controlled output based on battery
temperature, a highly recommended feature.
Recommended battery chargers are available
from Blue Sea, Charles Industries, ProMariner,
Mastervolt, and Newmar.
Ed Sherman is the Director of Educational
Programming at the American Boat & Yacht
Council as well as the author of several books,
including The 12-Volt Bible for Boats.
WHAT TO LOOK FOR IN
A BATTERY CHARGER
■ Proper amperage rating for the battery bank in amp hours you’re going to
recharge. Output should be 25 percent
to 40 percent of the battery-bank capacity in amp-hours. For example, if you
have two 100-amp hour batteries (200
total amp-hours), select a charger with
an output of 50 to 80 amps.
■ Temperature sensing for automatic
adjustment of charger output in
■ Programmability of the charger to
tenths of a volt for the various phases of
■ Battery-type selection. Flooded, AGM,
gel, and TPPL, etc. Equalization phase
for use with flooded-cell batteries, either
programmable or manually selectable.
■ Rated for ignition protection if going
to be installed in a gasoline engine room.
■ Multiple voltage and frequency input
capability, if using in an international
Bad Fuel can
Ruin a Good Day!
• Helps to prevent problems with all ethanol blends
• Encapsulates water in fuel systems allowing it to
burn harmlessly through the system
• Increases power & performance
800.530.6935 Eliminating water in fuel systems since 1965
We Make Water Burn!TM