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Comment by sokoloff | Hacker News Reader

> Oh, and its lifespan (7 years) is about twice that of a lead-acid battery (3-4 years).

I live in Cambridge, MA (so we get winters) and I can't remember the last time I've had a regularly driven car's battery fail in under 7 years.

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In Arizona, you're lucky if it lasts for 2 years. Batteries don't like being in 120 degree heat all day or something.

I've lived in both Cambridge, MA and Scottsdale, AZ, and my batteries routinely die in under 2 years. I think it's mostly a function of my (infrequent) driving habits.

> I think it's mostly a function of my (infrequent) driving habits.

Yup. I bought a Battery Tender[1] for my infrequently-used vehicles and now the batteries last indefinitely[2]

[1] http://amzn.com/B000CITK8S

[2] :) Based on the fact that I haven't had to replace them yet after 5 years.

I grew up in AZ, and I don't remember this being the case, so it's probably your driving habits.

Don't crank the terminals onto the posts that hard, you could be cracking the case very slightly.

I've never figured out why some batteries last and others don't. My '05 6MT V6 sedan still had its OEM battery when the starter finally refused to turn over in 2013. My wife's '07 5AT I4 sedan just got its fourth battery this month. My car grew up in central Kentucky, hers spent its first 3 years in New England before also moving to ol' Kintuck.

Not that this was necessarily the case with your vehicles, but battery placement in a vehicle will directly affect its lifespan. If it's closer to a heat source (e.g. the engine), it will die much faster. This is why some manufacturers put them in the wheel well or the trunk.

Depth of discharge can be very important. When lead-acids discharge, the metal in the electrodes moves into the electrolyte, making the electrodes smaller and weaker. Couple that with electrodes made very "spongey" to increase surface area to maximize the cranking current, and they can start to flake off and fall apart if discharged enough.

I'm glad you've been so fortunate. There definitely is some variation. There are a lot of outliers on the other side too. The 3-4 year number is what most manufacturers themselves claim.

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