Battery Equivalents and Replacements

Can You Use A Marine Battery In A Car

Both marine and car batteries share many similarities in terms of voltage, capacity, size, weight, CCA (Cold Cranking Amps), MCA (Marine Cranking Amps), chemistry, battery terminals, and similar.

When having issues with a car battery, replacing a car battery with a fully charged marine battery can be tempting, but can and should this be done?

Published: December 22, 2022.

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Marine Batteries vs. Car Batteries

Marine batteries and car batteries are very similar in terms of the following:

  • Voltage: most car and marine batteries feature 12V nominal voltage and are being recharged with a combination of alternators and charge controllers.
  • Capacity, Size, and Weight: depending on the power required to crank the boat's and car's engine, batteries differ in size, capacity, and hence weight. Most marine and car batteries belong to a certain size group, allowing the user to easier find a suitable battery.
  • CCA (Cold Cranking Amps) and MCA (Marine Cranking Amps): CCA and MCA describe the battery's ability to provide large currents under certain conditions. The larger the CCA and MCA, the better the battery's ability to crank the engine.
  • Battery Chemistry: most marine and car starting batteries are lead-acid AGM, Gel-Cell, or Wet/Flooded batteries, although some manufacturers offer drop-in lithium replacements.
  • Battery terminals are used to connect the battery with the boat's and car's electrical system. Marine and car battery terminals differ, but some manufacturers offer models with both types of terminals. If battery terminals don't fit the boat's or car's cables for whatever reason, one may use special battery terminal adapters and connect almost any battery to any cable.
  • Hold-down systems fix the battery and don't allow it to move around. If a hold-down system doesn't fit the battery, this can be remedied using various adapters and hold-down kits.

Note: although these days there are adapters and kits for everything, it is better to use none of them...

So, can or should we use the marine battery in the car?

Yes, if and only if the marine battery is of the same or very similar size, it has the exact chemistry as a car battery, has the same or better capacity/CCA/MCA and other discharge features, can be properly secured in its position, and can be properly connected to the car's electric system.

Note: modern cars are computers on wheels, and most of them are not "very happy" when the main battery is disconnected or fully discharged - this can trigger the alarm and block the engine completely, requiring the car to be towed to the certified dealership to unlock the car's engine.