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I know it's rare but I've had it happen twice. One was 11 years old exactly and the battery still worked good, but it was a side post ac Delco battery and the post rotted off. The other was a Toyota battery that was 13 years old when I sold the car with it. Both vehicles spent the majority of their lives outside in MN during the winter. All the other lead acid batteries I've had all seem to last 5-6 years max.
Cant say enough good things about Optima's, and sometimes when you think they are dead, they are not. If one starts to swell, or get bumps on top, then its damaged. But numerous times i have had people say their optima died, and they bring it over, and i resurrect it and it works again for years. This commonly occurs if you completely drain them to the bottom power wise, like ZERO. And most chargers will say its Kaput and refuse to charge them. But there is a trick.
Connect a regular lead acid battery to the trickle charger on its lowest setting, 2 amps or so, then take jumper cables, light duty ones are fine, and connect the "dead" optima to the lead acid that is being charged, positive to positive, negative to negative, and let it charge for 4-6 hours, maybe longer depending on the optimas capacity and how deeply it was drained.
After 4-6, maybe 8 hours, the Optima, assuming its internals are actually good, will suddenly be alive again, and now you can charge JUST the optima until its fully charged by itself.
First off, that is pretty cool you got 2 batteries in the stock location.
Secondly, I personally (just my own opinion) would stick to lead acid. I've had hit or miss issues with AGM. I've read that older alternators charging profile may not be 100% in alignment with charging profiles of AGM batteries. I am not an expert in batteries in any means, but I've had my best luck with lead acid.
Just my 2 cents, probably unneeded. I heard good things about AGM batterries so I got one when it was time for a new one.
I had 3 AGM batteries in a row puke between 3 months and 1 year, all covered under warranty, the fourth one has been great for the last 7 years. I forget the brand without going and looking. (I could.... I'm just lazy and heading to bed though)
My go to battery, for everything usually, is an Interstate Megatron. Lead acid and they usually last 10 years. One puked after 8 years but the other ones have all lasted 10-13 years. I have bought about 7-8 of them over the last 30 years.
The oldest one I currently have is 6 years old in the little 1600 Ford tractor, she was my first diesel.
Another leaded vote. The AGM does need a different charge profile then what these rigs are not set up for. Not saying wont run but you wont get optimal lifespan. Just not worth the extra cost when lifespan is factored out (since you wont get full lifespan due to charging profile).
Another leaded vote. The AGM does need a different charge profile then what these rigs are set up for. Not saying wont run but you wont get optimal lifespan. Just not worth the extra cost when lifespan is factored out (since you wont get full lifespan due to charging profile).
My AGM battery experience is with a 1985 Corvette, my Interstate battery experience is with my trucks, Ex's, SUV's, and farm tractors.
So my experience may not be apples to apples per say.
The thing that kills AGM's early, more then charging profiles and such, is deeply discharging them to the point they seem dead, letting them stay that way for a day, several days, or worse, longer, repeatedly. If you keep them charged at least 75% they last ridiculously long. I have the same yellow top in my 07 GT thats been in there for 5 years now, its been parked for months at a time, and always fires right up, i have a solar panel on it so it doesnt allow it to deep discharge. Proper maintenance.
"Many regulators have too low output voltage to properly charge an AGM battery. Typical regulator setpoints are 13.5V to 14.4V. These voltage levels are enough for most of the bulk charge stage, but a bit too low for a proper absorption charge, which would take a voltage between 14.2V and 14.9V depending on the temperature and the battery model. For more info, see my articles on AGM charge staging and voltages.
On a typical car charging system, an AGM battery will therefore charge slow, and never quite to 100%. This will cause fast capacity fade and lead to a short battery life."
