Thinking about converting a car to run on electricity? If you are, then before you shell out your hard earned dollars you’re probably wondering just how long your shiny new batteries are actually going to last.

The answer to the question of how long electric car batteries last depends on the battery chemistry. All are different, and each battery lifespan depends on how they are treated. If you cycle your batteries (drain them and then “refill” them) often, then they’ll generally have a much shorter life.

I’ve even read stories of lead acid batteries – normally lasting just 3 years in electric car applications – living well beyond 25 years as backup batteries in telephone exchanges. These massive battery packs often sit fully charged all day & night, waiting for a power cut. Most telephone exchanges also have diesel generators which start immediately too, so the batteries are only briefly used except their yearly testing.

But electric cars are why we’re here, so let’s look at the average battery lifespans of common battery chemistries if they’re used in electric vehicle applications.

Normal Car Starting Batteries: 3-12 months
Marine Batteries: 1-6 years
Golf Cart Batteries: 2-7 years
AGM Deep Cycle: 4-7 years
Gelled Deep Cycle: 2-5 years
Ni-Cad Batteries: 1-20 years
Ni-MH Batteries: 2-10 years
LiFePO4 Batteries: 6-10 years

Batteries are very different things. I know, it almost seems a stupid thing to write, but it’s true. Each chemistry has a different weight per “kilowatt-hour” (a common unit of electricity). The different types also have different recharging & monitoring methods to ensure long & useful lives. Each chemistry also has a different environmental impact depending on it’s recyclablity, and perhaps most importantly, each chemistry has a very different cost.

Lead batteries (the first 5 batteries in the above list) are still king when it comes to electric car applications. This doesn’t mean they’re good, it just means they’re cheaper when initially purchased, compared to, say, Ni-Cad batteries. Though as you can see, Ni-Cad batteries can outlast lead batteries incredibly. You’ll have to work out your replacement cost versus lifespan individually.

The newest kid on the electric block would have to be Lithium Iron Phosphate (LiFePO4) batteries. They’re still a new technology compared to lead acid batteries, which means we’ve not yet seen examples of long term usage in electric vehicles and won’t fully know their lifespan characteristics for another decade to come.

That being said, if the estimations are correct and they last beyond 8 years per pack, LiFePO4 batteries appear much cheaper than traditional lead batteries in overall ownership costs. This means while a higher initial cost, LiFePO4 batteries will cost less in the long run, with many fellow converters making the move to lithium.