Marine Battery Care

By Capt Andy LoCascio - 11/29/2016 - Short URL: - Views: 42177

Odyessy BatteryA marine battery takes an incredible amount of abuse.  In the Northeast batteries sit idle in freezing temps during the winter lay-up period.  Most boat owners may go days without using their boats and even then don’t run the boat long enough to do much charging.  Fishing boats are notorious for having various electronics that drain the batteries including bilge pumps, bait pumps, washdowns, lights, sonar, radar, stereos, and others.  When you factor in the marine environment and a few corroded connections you have a recipe for a disappointment.

Testing Your Marine Battery - Step by Step

An inexperienced boat owner will often simply replace a marine battery without ever considering the cause of it’s demise or even knowing if it is truly beyond saving.  Here are a few simple steps that can help you make that determination:

Time requred: About 1 Day 14 Hours

Supplies needed:

  • Distelled Water (unsealed batteries)

Tools required:

  • Battery Load Tester (optional)

1. Disconnect Battery

Disconnect the battery completely. This is important in case you have an issue with something draining the battery.

2. Check Fluid Level

If your battery is not a sealed battery, pop off the caps and check the fluid level. If the level is not up to the base of site port, add distelled water.

3. Charge Battery

Use a trickle-charger to charge the battery for 24 hours. Most trickle chargers produce around 3-6 amps.

4. Rest Battery

Let the battery sit for another 12 hours and use a simple DC volt meter to test for a dead cell. A 12 volt battery should show around 12.6 volts. If it shows much less than that, one or more of the cells is dead or dying.

5. Load Test Battery

Invest in an inexpensive load tester (approx. $35) and perform a load test. If it passes, you are good to go. If not, time for a new battery. If you do not have a load tester, skip to the next step.

6. Reconnect Battery and Retest

Simply hook the battery back up and immediately try to crank your motor. If it cranks fast and hard, your battery is probably good to go. If not, you still may have a good battery, but a bad connection to the motor.If your motor will not crank quickly, connect a booster charger to the terminals and see if cranks. If not, you have a connection issue. If it cranks fast and hard with the booster, the battery is dead.

Charging Your Battery

Automatic Marine Battery ChargerNever use a booster to charge your marine battery.  A booster should only be used to start the motor and then removed.  If you leave a booster on for any significant length of time, you may permanently damage the battery.  Always use a trickle-charger.  Serious boat owners invest in a full time automatic charger that senses the battery charge and charges appropriately.  If you have multiple batteries, you should purchase a charger that will manage all of them individually.

Maintaining Your Battery

If you have a lead-acid marine battery with battery caps, pop the caps off and check the level in the battery.  The level should be just at the bottom of the tube.  Be sure to check all six cells.  ONLY use distilled water (found in most drug stores and super-markets).  Regular water has dissolved minerals and salts that will harm the battery.

Sealed batteries require no maintenance other than keeping the terminals tight and clean.

Marine Battery Terminals

Corroded Marine Battery Terminals

Corrosion on battery terminals

It is critical that battery terminals are absolutely clean and properly tightened.  If a terminal is warm (or hot) to touch, the connection is poor.  Periodically remove all the connections and clean the posts and terminals.  Replace the connections and spray the terminals with some type of corrosion preventative.  Even the slightest bit of corrosion will affect the battery performance.

Is Your Battery Getting Charged?

Most motors (expect for the smallest outboards) have alternators that provide electricity to operate and motor and a charging circuit to charge the batteries.  Use a volt meter and you need to see at least 13.8 volts.  If you see much less than that (but still higher than the 12.6 volts the battery produces), you probably have a bad connection somewhere.  If you still see 12.6 volts (battery voltage), you either have a bad connection or an alternator problem.

Marine Battery Troubleshooting Tip

Often times, marine batteries are being drained when the boat is not in use.  With all the switches off, connect all the ground wires to the grounds terminal.  Then attach the positive wires carefully watch for any sparks.  If you see any, that means that something is drawing current (a stuck automatic bilge switch is a typical culprit).

Freezing Temps for Marine Batteries (Winterization)

Marine battery damage caused by freezing

Marine battery damage caused by freezing

Nearly all batteries lose about one-third of their power when the temperature falls below freezing (32 degrees Fahrenheit or 0 Celcius).  Batteries can actually freeze and if they do, they are ruined forever.  The plates will bend and the casing will crack.  However, a fully charged battery will not freeze until temps reach well below -50 Fahrenheit.  A fully discharged battery can start freezing at the same temps as water.  It is important to note that a fully discharged battery is only 12 volts or less.  It is critical that a battery is fully charged as part of the winterizing process.  If the boat has been hauled, it should be disconnected from the electrical system to avoid discharge.

By Capt Andy LoCascio - Host of Northeast Angling TV
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