This articles looks at starting and house batteries.

House batteries are expected to just about everything except start the engine. They provide the power for things such as lights, electronics, pumps etc.

When selecting batteries for house use you need a deep cycle battery. Inside the battery are fewer, thicker plates. These batteries can be run down and charged 1000’s of times.

It’s important to look at the number of amp hours when picking a house battery. The standard time measurement for amp hours is 20 hours.
If a battery is 100 amp hours, it will produce 5 amp hours for 20 hours or 10 amp hours for 10 hours, etc.

Starting batteries are special purpose batteries. They are made to provide a lot of power quickly. The figures are in the 100’s of
amps for a period like 5 seconds. These batteries are not made to be deeply discharged as are house batteries.

A key # for starting batteries is cold cranking amps. This figure will show how many amps a battery can deliver for 30 seconds
at a temperature of 0 degrees F, until the voltage frops from 12 to 7.2 volts.

Requirements for starting batteries range from 70 amp hours/400 Cold Cranking amps for 1-3 cylinders to 120 amp hours and 660 cold cranking amps
for larger 3 and 4 cylinder engines. Since cranking an engine for 30 seconds is extremely abnormal, you really get more amps for a marine engine in good order.

There are also dual purpose batteries. For boats with minimal power needs, that recharge batteries frequently a pair of these can be a good choice.

For boats that are going to do extensive cruising or decide to become electronic intensive with refrigeration, computers, inverters etc., separate house and starting batteries are necessary.

Next week we’ll look at auditing you boat’s power needs and determining the battery requirements.

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