I've been playing around with an Optima Yellow Top for about 3 months, draining and recharging the battery. I think I've done this about 6 times now, from 13volts down to about 8 volts. It seems to be still holding a full charge after a recharge. I'm somewhat impressed so far........
OK.....so are you saying that you think the results would be any different with other high quality AGM type batteries under the same conditions ? If so, what leads you to believe that ??
I was reading that Toyota batteries are not good at constant deep discharges. Optima calls their batteries "deep cycle" to not be affected by deep discharges and is able to still operate normally after discharging fully. To my understanding, Toyota batteries aren't as good at that. So I put the optima battery to test to see if this "deep cycle" holds true, and so far, it holds true.
I would say that 8 volts is too low for any type of lead acid battery. At that point irreversible changes are taking place. 10.5V is about the limit if you want longevity.
But if you want to REALLY stress it as a test you probably would want to go beyond the "normal" limits. I do agree with you though........and wonder what he intends to DO with this test battery after he is done testing. I certainly would NOT trust it in my car.
It's an extra battery, not sure what I'll do with it. Right now it's used to power my equipment in my garage, attached an inverter to it. It's not used all the time, so basically simulating being in a car that sits for a while. The voltage doesn't seem to drop over a 2 week period, so it does hold its charge.....but saying that, it is a new battery from Dec 2013.