Hey IT Nerd! What’s An AGM Battery?

I must really be popular with those who like cars as I keep getting questions relating to cars. Such as this one that hit my inbox last night:

Hi IT Nerd. I need to get a new battery for my car and one of the battery options at my local shop are something called an AGM battery. The kid at the shop says they’re better but couldn’t explain why. Can you explain why this battery is better?

Thanks for the question and I can explain why.

An AGM (absorption glass mat or AGM for short) battery is a type of battery made up of mats in which thin glass fibres are woven to increase the surface area and instead of having lead acid surrounding these mats, the mats are soaked in the acid just below the point where they would become saturated. That way there is no potential for leakage and it makes the battery lighter than a traditional lead acid battery. There are other advantages as well:

  • If you drive in extremely cold temperatures, AGM batteries will deliver more cold cranking amps. That also helps with vehicles that have large electrical loads such as minivans with DVD players.
  • If your alternator dies, you can likely limp home as AGM batteries will have longer reserve capacity.
  • AGM batteries are a better choice for those who drive short trips as they recharge faster.
  • If you leave your lights on and you need a boost, an AGM battery will recharge faster.

Thus if you have an option to go for an AGM battery, you should. You’ll pay a bit more money, but you’ll get better battery performance and likely a much longer replacement warranty out of the deal. Another thing to note, many luxury cars come with AGM batteries as standard equipment because of the fact that as I noted above, they save weight which means slightly better fuel economy. After all, batteries are typically heavy.

Oh, some free advice based on learning this the hard way a couple of summers ago. You should replace your battery every 4 to 5 years so you don’t have an unexpected surprise at the worst possible moment.

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