What's the difference between a car battery and a deep cycle battery

If you’re researching batteries for your car or boat, you’re bound to come across two different types of batteries in your Googling – deep cycle batteries (sometimes called marine batteries) and plain old car batteries.

These are two very different types of batteries with very different uses, so it’s essential to understand how to best use each type of battery and what kind of vehicle they suit.

Car Batteries

Car batteries have been specifically designed to provide your vehicle with a short and sharp burst of power in order to start your vehicle. Power to things like the radio, headlights, display buttons, windows, etc is fed through the alternator. The battery is purely there to provide enough charge to start the vehicle. Once the car has started, the alternator also puts the charge back into the battery.

Car batteries aren’t good at providing long term current over extended periods.

Deep Cycle Batteries

Deep cycle batteries are usually made from denser, thicker material when compared to car batteries. This helps them to resist repeated charge and discharge cycles over long periods. Essentially they’re almost the opposite of car batteries in that they are designed to deliver sustained power at a lower current over extended periods.

What happens if you use a car battery for a deep cycle application?

Some people will think they’re saving money by purchasing a cheaper car battery for applications usually relegated to a marine or deep cycle battery (we’ve seen this done by many weekend campers).

It’s true that if you hook up a car battery to your camping rig, caravan system, etc it will power your electrical items for a time, but using a car battery in this way will not only damage it (which means you will need to replace it sooner rather than later) it will also place it outside of any warranty claims as it wasn’t used for its intended purpose.

By hooking up a car battery to a camping rig, caravan rig or boat, you will be drawing low charge from the battery over extended periods of time, which isn’t what the battery is designed to do, thus depleting the charge capacity of the battery quicker than expected.

Can you use a deep cycle battery in a car?

Technically yes, but it’s a little like using a circular saw to cut up a roast chicken. It might do the job, but you’re not using it for its intended purpose. The surge required from a battery to start a vehicle is quite high, and deep cycle batteries are not designed to have that much draw taken from them. This often causes damage and shortens your battery’s lifespan considerably.

So as you can see, whilst there could be some crossover usage for car and deep cycle batteries, they’re both built in very different ways, for very different purposes. Using one type of battery for another's application is just asking for trouble, and that’s the last place you want to be when you’re in the middle of nowhere or hours away from civilisation.