A boat-marine-ship will use two different types of batteries:
1. A marine starting battery is used to turn over the boats engine. These batteries come in various sizes depending on how many CCA (cold cranking amps) or Marine Cranking Amps MCA the engine needs to crank. (Click to See Battery Terminology & Definitions)
2. A deep cycle battery sometimes called a “house battery” is used to power the lights, pumps, instruments & navigation.
- Starting batteries for marine range from relatively small 12 volt group size 24 to large 12 volt 8d batteries weighing 120lbs each.
- AGM and Gel batteries are popular with boat owners because they are sealed and don’t require regular water level maintenance.
Because starting batteries have thinner plates than 6 volt deep cycle batteries, deep discharging the 12 volt battery damages the plates and reduces the batteries life cycles.
Starting batteries should never be used for deep cycle applications.
- 12 volt Dual Purpose / Marine Batteries are a mix of starting and deep cycle battery properties. Use for light deep cycle applications only.
- Deep cycle 6 volt batteries have thicker plates and are able to deliver long term energy. If you’re cruising long range, you will get more available power with two or four 6 volt batteries. (See wiring diagram for 6 volt batteries)
- If you are looking for a comprehensive guide to marine batteries, David Pascoe as everything you need to know in one article.
- To avoid annual battery replacement, deep cycle batteries will perform best when charging is completely reliant on engine alternators since cranking batteries do not tolerate deep discharges well. Further, if you’re going offshore where there may be high demand on bilge pumps, BEWARE that cheap automotive batteries aren’t going to run your pumps for very long, particularly after engine failure. Offshore operators should use higher capacity deep-cycle batteries.
Marine Battery Buyers Guide