Never heard of anyone having probs switching to AGM. I did just have a weird experience though.
I had an old yellow top Optima that history was unknown.
It was weak when I put load tester on it and it dropped to 9.5-10.5 v.
I figured it was shot but I put in on charger.
I have an electronic one with AGM and gel settings.
It charged up fine to my surprise. Then I ran the reconditioner/desulfate 2-3 cycles.
And charged it again.
Load test was AWESOME! I will say these AGM are impressive under load. NOT over $200 impressive BUT they sit with full batter load tester on them for 20 secs and never drop below 11.2 usually staying at 11.5.
A regular battery will be 10.7 on a good day.
So I let it trickle. Then let it sit for 10+ days. Load test still awesome!
Had a batt get weak in a car I was using but only driving every 10-15 days.
Put it in and drove it 2 times. 1st was driving and idling for over 6 hrs. I did turn it off once or twice and it restarted just fine.
A few days later It started right up and I drove it 6 miles, idled for 15 mins, then 5 miles.
Shut if off and sat there for 45 mins and it was TOO low to start!!
Had to use the battery backup.
Now this is where it gets different. This is on a limo with two separate charging systems.
They are completely isolated For all intents and purposed UNLESS you push the batty backup button and that just energizes a solenoid that connect the rear batt to the front batt.
The front factory ford is stock with its alternator and the rear has its own battery and own alternator. This alternator is not engergized or producing current until the back main power button is turned on.
So I drove it the 10 miles back to base and it was fine. Turned it off and let it sit for 15 mins, turned head lights on for a few secs and could tell it was weak. Would barely crank.
So this optima seemed great until I put in in a car and used charged it with alternator. I wonder how easy they are to damage?
Limos often crank up voltage to compensate for extra loads but this has two factory alts with internal regulators.
It has a digital aftermarket volt meter an I see 14.7 often when it is first started.
Wonder if it killed the batt or it was just shot to begin with and that is why it was replaced....It was old used batt.
It was so great out of car under load test and sitting for days with no loss of voltage or capacity.
This is my 1st experience with an optima so it's a little confusing.
Aren't they supposed to be safe for up to 15 or 15.2 volts?
I don't think the car had any fast drains in it. It sat with another battery in it for weeks and still started right up.
I haven't tried to charge the optima yet. I wouldn't trust it anyway but if it doesn't charge and won't take a load then at least I'd know its shot.....just not know if the car damaged it.