A rant on pro-rating.

I get a battery every 2-3 years whether or not I want it. I think the way my car is wired with all the factory wiring and the aftermarket radio plus the 60amp alternator results in dead batteries. I want to put the larger battery and alternator on for harsh climates just in case I get all the electrics working.

My bike is weird, I think the battery is dying so every 2-3months I charge it 24hours and it still works.

In reply to confuZion3:

my old roommate ran one of the lawn & garden batteries in his 626. if it'll crank over the ole f2, it'll work in a miata. you'll need the terminal adapters to hook it up to the L&G battery posts

I don't consider a battery a 'wear item' like tires. Yes, they have a finite lifespan, but unless abused - it should be reasonable to expect a battery to survive the warrantee period. That said, I think you have to know going in that the warrantee isn't worth much if you have a failure.

For what it is worth, just this summer my VW got it's third battery since new. It is a '92, so the first two batteries lasted a combined 17 years.

I have a lawnmower battery in the Miata. Same CCA rating as the stock battery, the only difference I could see was the posts. I paid $20 plus $6 for post adapters, instead of the $100 I was quoted for the standard Miata battery. No problems since April or so.

Different areas have different battery life. My B-I-L in Texas can get an easy 5-6 years. But they don't have sub zero temps and harsh winters. Here, 3-4 years is about the norm. Considering winter can be -20 and summer can be 100... and a little everything in between. How much a car is driven, the type od driving... deternining a life for a battery is less likley than figuring a real lifespan for new tires.

Bobzilla wrote: Different areas have different battery life. My B-I-L in Texas can get an easy 5-6 years. But they don't have sub zero temps and harsh winters. Here, 3-4 years is about the norm.

Northern MN has been brutal on my batteries (no real shock there). While I can get 3+ years out of them, they usually get replaced @2 so I don't actually have to deal with them failing when I need them.

I seem to get 5+ years out of batteries in the Mid-Atlantic. 97 Miata with 130,000 miles is on it's second. The 2002 Volvo was on it's first when we traded it a few weeks ago at 99,000 miles. The 2006 Lexus is on it's second or third (bought the car used, not sure, just know it's not original).

My Tundra is officially on its 9th year with the same battery. I am amazed - considering I've accidentally deep-cycled it many times. I will replace it this fall before it gets cold but... part of me wants to see just how long it will go.