💬 Fork of BigClive AA Battery Trickle Charger
openhardware.io last edited by openhardware.io
I have an assortment (pictured) of older AA NiMH batteries. Rather than trusting BigClive's trickle charging idea to fate, 1. I think I'll capacity test each of them plus a few others as controls, 2. record the measured capacity on each of the cells, 3. let the charger trickle charge the treatment group of batteries (i.e. those which are not serving as experimental controls) to maintain their charge, and 4. re-test the capacity of all the batteries from time-to-time to see if the capacity of the trickle charged batteries is degrading any faster than the control group batteries.
It's easy to imagine ways in which adding an MCU to the equation might improve the charging/maintaining of the batteries, but if it turns out that BigClive's approach works just fine without any negative consequences, then keeping the design simple, such as it already is, may be the greater virtue. On the other hand, if big improvements are possible, then that would be good to know as well.
In order to properly test it, I should probably start with all new batteries. I did capacity testing on some of the older batteries and then retested their capacity again to see if the numbers matched. They didn't. So, given the small sample size, I'd be weary that there might be too much noise in the sample to draw conclusions if I start with batteries that are already impaired.
What became clear though is that batteries which just sit in a drawer can degrade quite a lot, and that it's not from overuse or re-charging. That's just what happens to NiMH batteries as they age. I guess it shouldn't be surprising, because that's what we expect from alkaline batteries also. But maybe some of the impairment was due to allowing their charge to fall while being stored? That seems to hold true for SLA batteries. Not sure about NiMH batteries.
So, unfortunately, I just don't have the data to say what the effects of trickle charging might be. If it turned out to actually extend the useful life of rechargeable batteries, then that would be an interesting outcome. Maybe someone reading this will feel inspired to conduct such a test and post the results.