Marine Engine Battery Care
Bulletproof Your Boat's Batteries
NO MATTER HOW DILIGENTLY YOU CARE for marine batteries they have a lifespan that's limited to a few seasons at best (with the longest-lasting batteries being the AGM variety). Neglecting a starting or deep-cycle battery during spring commissioning is guaranteed to diminish its effectiveness and shorten its service time.
If you must replace a battery, make sure it's the same type (flooded, gel or AGM) as its companions. Also, don't couple a new battery with an old one, because the weakest link will rule. A "smart" charging system is your best insurance against too much or too little amperage being delivered during a charging cycle. Maintenance also ensures that batteries will perform up to spec. Here's how to do things right.
Every couple of months during winter storage, you should have trickle-charged the battery. If you haven't done this, your battery is probably deeply discharged, which has a negative effect on its longevity. During spring commissioning, top off low electrolyte (flooded cells only) then charge the battery. Let it sit overnight. Next morning, measure voltage with a voltmeter. It should read 12.7 volts. If the charge registers 11 volts or lower, the battery is dead. If you don't have a voltmeter, simply try to start the engine. Assuming the starter motor or solenoid didn't die during lay-up, the engine should at least crank over. If not, you're in the market for a new battery. If you're unsure of your results, seek out a pro whose more sophisticated battery tests will precisely measure the health of your battery.
Long Term Smart Charge
Install a "smart" onboard battery charger. The best ones trickle charge, which extends battery life and ensures that the engine will start at 4:00 a.m. on Saturday. More sophisticated models go one step further, and de-sulphate the plates. De-sulphating electronically sloughs off dead plate material, extending a battery's life expectancy by 25 to 100 percent. Plate treatment must begin when a battery is new for best results.
Clean the Terminals and Posts
Battery posts, terminals and cables must be clean and shiny. Green, gritty corrosion blocks outbound current flow to the starter motor and electronics and resists inbound charging from the engine alternator. A battery terminal cleaner with male and female wire brushes gets the job done quickly. Clean the battery top with a solution of baking soda and water, being careful not to let any get into the cells.
Prevent Corrosion on the Terminals and Posts
To prevent the return of corrosion lightly grease the posts and connections. Or simply spray them with a coating of terminal protecting solution. I go one more step and coat cable terminal ends after installation with liquid electrical tape, a rubbery liquid that hardens and insulates. It forms a barrier coat against corrosion. It can also prevent corrosion from creeping like a vine down the inside of a battery cable. Before installing the cables I slip an anti-corrosion ring on each post. These felt washers, saturated with a neutralizing agent, absorb acid leaks around the terminals, discouraging corrosion formation.