Are deep cycle batteries different than regular automotive batteries? I get asked this question a lot.
"I'm converting an electric car. I see that the "traction" or deep cycle batteries for EVs are pretty expensive, while the DieHards at my local auto parts store are relatively cheap...and they're both lead-acid auto batteries, I see. So, can I save myself a pile of cash by putting those auto batteries in my electric car?"
Answer: No, because not all "lead acid" batteries are the same.
It's true that one battery looks a lot like any other battery, and they take up just about the same amount of space in your battery compartment (depending!), and they both make use of lead-acid chemistry to store electrical power. But that's where the similarity ends! Let's talk a little about the differences.
Gas-gobblers have cranking automotive batteries, called SLI for Starting, Lighting, and Ignition, and is designed to deliver a lot of juice at once. It is intended to give up about 5% of its charge before charging back up again off the alternator. The electrolyte plates inside the SLI battery look like something like a large wad of foil which delivers a lot of surface area for the weight, but it's delicate.
The ones you need for an electric car are deep cycle batteries, meaning they don't have any objection to being drained down to 20% of their full charge, and then recharged...over and over and over again. The electrolyte plates inside deep-cycle batteries are often solid metal, heavy but sturdy.
If you put a bank of SLIs in your Xebra thinking you'll save yourself some money, you'll put them under extraordinary strain; that happy wad of electrolyte foil will soon be powder sediment resting on the bottom of Lake DieHard...
...and you'll be WALKING.
There are now over 3500 entries in the EV Photo Album, and of all these electric cars, tractors, bikes, and motorcycles that people have bought or converted, the most common EV battery type is the 6 volt flooded lead-acid deep-cycle golf cart battery made by Trojan.
These golf cart batteries are also a hybrid-type traction battery, but have a longer cycle life (number of times you can drain it and charge it before it dies) than marine batteries.
Chances are, this is the type you'll be using, too.
How batteries work - a primer.