A car battery is a starting battery: it delivers a big burst of current for a few seconds to crank the engine, then the alternator recharges it right away. A marine battery is built for life on a boat, with sturdier plates, better vibration resistance and, depending on type, the ability to be drained and recharged repeatedly. Marine batteries come as starting, dual-purpose and deep cycle types. A car battery can crank a small outboard in a pinch, but it will fail quickly if used to run a trolling motor or electronics.
Marine battery vs car battery
| Car battery | Marine battery | |
|---|---|---|
| Main job | Short, high-current engine starts | Starting, house loads or trolling, depending on type |
| Deep discharge | Damaged by repeated deep discharge | Deep cycle and dual-purpose types handle it |
| Construction | Many thin plates | Thicker plates, more vibration resistance |
| Rating | Cold cranking amps (CCA) at 0°F | Often marine cranking amps (MCA) at 32°F, plus reserve capacity or amp-hours |
| Terminals | Posts | Often posts plus threaded studs for ring terminals |
Can you use a car battery in a boat?
For starting only, a car battery can work short term, but boats sit for long periods, see vibration and pounding, and often draw power with the engine off, which shortens a car battery’s life. For a trolling motor, no: a trolling motor drains the battery deeply every trip, which a starting battery is not built for. See deep cycle vs starting battery.
Which marine battery do you need?
- Starting: cranks the outboard; recharged by the motor’s charging output.
- Dual-purpose: a compromise for small boats with one battery.
- Deep cycle: runs trolling motors and electronics; see trolling motor battery life.
Lithium marine batteries
Lithium iron phosphate (LiFePO4) deep cycle batteries are lighter, deliver most of their rated capacity and last thousands of cycles; see lithium vs lead-acid. We carry the Ionic 12V 300Ah LiFePO4 deep cycle battery with Bluetooth and heater at $1,599.00 and LBP lithium battery bundles at $970.00.
Flooded, AGM and lithium
Marine lead-acid batteries come as flooded (wet) cells, which need their water level checked, and sealed AGM batteries, which are maintenance-free and handle vibration well. Lithium is the third option for deep cycle use. Whatever the type, match the charger profile to the chemistry, because charging AGM or lithium on a flooded-battery profile shortens its life.
Keeping marine batteries healthy
- Charge after every trip with a marine charger; see how to charge trolling motor batteries.
- Turn the battery switch off when the boat is stored.
- Secure the battery in a box or tray and protect the terminals.
If a boat battery keeps going flat, see boat battery keeps dying.
More guides: boat battery switches · LiFePO4 vs lithium-ion.
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