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AGM battery and heat.

9K views 7 replies 5 participants last post by  PDXsailor 
#1 ·
Hello,I was reading about AGM batteries. Mostly over my head. However,one thing stood out. They do not like heat and should not be used in the engine compartment. So I looked and sure enough,in the engine compartment of my hybrid is the AGM battery. Is that info wrong? Or is that going to mean shorter life?
Thanks.
 
#2 ·
Where are you reading that AGM batteries don't like heat? I've used AGM batteries in my motorcycles for years and they're great. In my experience, the AGM batteries last longer than lead-acid. Safer, too.

Both my MDX and my wife's Infiniti came with AGM batteries from the factory -- both are in the engine bay.
 
#3 ·
I think it's generally true that all batteries would prefer to be protected from heat (and cold) which is why most new cars have insulation on them. I think I read too that the MDX has a vent tube that goes from the front fascia and into the battery compartment to aid in cooling?

My Chevy SS also has an AGM battery but its mounted in the trunk. It's not always practical to mount them away from the engine compartments but it does isolate them from heat and in the case of a sports car helps a little with weight distribution.
 
#5 ·
I would not worry about heat in an automotive application - most of the time air is blowing past at a pretty good clip. I have used gel batteries in my boat for a couple of decades, and they are located next to a very small and poorly ventilated engine compartment, while in the tropics (hot air and water). Under heavy liveaboard and cruising use they last about 7-8 years. Of course I use proper charge regulation but I suppose that Acura does something similar.

AGM and gel batteries deliver power with less voltage sag under heavy load than a flooded battery, and can be charged faster as well. They are also able to survive a deep discharge better and can withstand shock loads better (particularly the AGM). Clearly the AGM is a better choice than flooded for our purposes. Gels are slightly better than AGMs in most things, but not worth the higher price in this application.

A technical point: these (flooded or liquid electrolyte, AGM and gel) are all lead-acid batteries; using "lead-acid" to refer to a flooded battery does not distinguish it from the others. FWIW a new technology is slowly appearing, called carbon foam; it sells for a bit more than the gel batteries and can operate over a wider range of discharge without harm (and weigh less IIRC). They are not justifiable for a car but they are being adopted by cruising sailors and RVers.
 
#8 ·
It depends what you mean by more powerful. It doesn't have any more stored amp-hours than a flooded battery. But as I posted earlier it can deliver more current with less voltage sag, so more wattage, with high loads such as starting motors. And conversely will accept more current without raising the voltage during charging, for faster charging. Voltage sag can cause all sorts of problems with electronic equipment, which is a big part of the MDX, so avoiding it is important. Replacing the AGM battery with a flooded one might result in issues with voltage drop during starting, at least as the battery ages.
 
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