Quote Originally Posted by fogging_katrider View Post
Why would you need to rotate them at all ?
Please correct me if I'm wrong, but wouldn't the batteries equalize themselves anyway while they're running paired as a stack ?
So why would alternating which one is on top have be beneficial to the paired stack ?
Quote Originally Posted by Rickajho View Post
The theory is that battery closest to the positive post drains faster. From personal experience I have found no truth to that theory.

But regarding what you said about "wouldn't the batteries equalize themselves" - no, that doesn't happen on any level and it's important, especially if people try to stack batteries in a mechanical. One battery will almost always hit low voltage before the other one does. An APV that is going to shut down when it sees 6.4 volts in stacked mode has no way of knowing if one of those batteries is still providing 3.8 volts - while the other one is all the way down to 2.6 volts. All it's seeing is the total series voltage output coming off the stack. In a mechanical there is no electronic monitoring at all, so the risk of that spread between two different batteries as they discharge can be even worse the further you push discharging them.

That's why you need to keep them in matched pairs and monitor battery voltages to make sure they are still remaining as reasonably close as possible to a matched pair over time. If one battery keeps depleting a lot lower and faster than the other one that's when bad things start happening to battery chemistry.
I have seen the bottom battery dropping lower and then losing more while sitting when I wasn't rotating. I can't say for sure whether it was the lack of rotating or if it was just that battery, although it's not happening in another set that I am rotating and I've taken to not rotating the bad set the other way and it seems to be equalizing.

I've noticed that not only monitoring charge voltage but discharge voltage is important.