Procedures to Trickle Charge a Marine Battery

Trickle charging a marine battery is a method of keeping your battery ready for immediate use during the summer months. Trickle charging helps ensue that your battery doesn’t die in the middle of the lake, leaving you stranded. A trickle charger is also a maintenance plan for the winter when you are storing your boat. The continual influx of electricity into the battery helps prolong its life and allows it to work more efficiently.


A battery charger will have an electrical cord and two cables, usually with clips on the end of them. Connect the black wire/clip to the negative (-) post of the battery, then connect the red wire/clip to the positive (+) battery post. After the clips have been correctly connected, plug the battery charger into an electrical outlet. There should be a red light on the charger; the light turns green when the battery is fully charged. Disconnect by unplugging the electrical cord from the wall, then removing the clips from the battery posts.

Charger 101

A marine battery charger needs to be rated at 1.5 to 2 amps, which means that your battery charges at 1.5 to 2 amps per hour. By providing a slow charge, your battery’s life will be maintained for a longer period of time. The low amperage charge also keeps the battery from overheating. With a fast charge, a high amount of heat is generated, which can destroy your battery by welding its internal plates together. To prevent the charger or battery from overheating, don’t leave the charger connected to the battery for more than 24 hours.

Over- and Undercharging

Either over- or undercharging a battery can have severe consequences, usually resulting in a destroyed battery. By continually using an undercharged battery, a buildup of sulfur occurs on the internal plates. This buildup hardens and eventually does not allow recharging of your battery. Overcharging a battery can cause it to overheat, which reduces the life expectancy of the battery. Should your battery, or charger, feel hot to the touch, disconnect the charger immediately before irreversible damage occurs.

Charger Types

In the marine field, there are on-board charges, which allow a continuous slow (trickle) charge to enter the battery during use, thus keeping it working for a long period of time. Other trickle systems can be carried on the boat, again allowing a trickle charge during use. You should consider a waterproof battery charger to provide protection to the charger itself. Solar powered trickle chargers are available and used during maintenance of the board and during regular use.