Reader Question: AGM Batteries?

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Here’s the latest reader question, along with my reply! 

Chad asks: What do you think about absorbed glass mat batteries vs. standard lead acide batteries?

My reply: Both types are lead-acid batteries; the difference is the AGM battery hasn’t got its acid sloshing around inside it. Instead, the liquid acid is absorbed on fiberglass matting. The great upside is spill-proofing. Conventional lead-acid batteries often leak acid, which will corrode whatever it comes into contact with.

AGM batteries are especially popular with motorcycle owners for their spill-proofness (bikes lean when they corner and the old liquid-filled batteries would invariably drip/leak acid onto the bike’s frame) and if you dropped the bike or laid it down, it was a sure bet the acid would dump all over everything… but AMG batteries also increasingly with car owners, for that reason and also because they are lighter and hold charge better/longer. They are also less prone to losing their acid through sulfation (see here for more details).

They are more expensive – generally, about 25 percent more than an otherwise equivalent high-quality liquid lead-acid battery. But the cost is going down and even if it stayed the same, I consider it worth the extra expense for all of the reasons detailed above and because you will probably get more life out of the AGM battery. I have AGM batteries in all of my motorcycles and my classic car, which only gets driven once or twice a month. I’ve been using them for years and have found they last years longer than a liquid lead-acid battery, with the caveat that you exercise correct charging procedures for these batteries (see here for info about that).

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  1. AGM batteries hold up to hard knocks and vibration much better. I’ve had them last much longer than conventional batteries. One of the best things about them is the lack of corrosion on the terminals. I had two sets last 8 years each. They “seem” since there’s no way I have to measure it, to have more power than other battery types of the same CCA rating. And their non-splashing feature leaves them clean their whole life. I’d continue to buy them just for the corrosion they don’t have. Your battery cables stay just like they were when you installed them. I detest finding corrosion well into the cable itself and having it build up continually even though you clean them occasionally.

    • I’m going to have to check into the price differential. The pickup and the jeep are probably going to need batteries soon 🙁

  2. AGM batteries are better. I have ’em in my scooters. They hold a charge for weeks at a time! I let my Burgman scooter sit for the better part of two months earlier this year. The original battery might have had enough charge left to light up the instruments, while the scooter started right away with the AGM battery. After having had AGM batteries, I’ll never look back!


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