During all my years of driving electric touring cars there has been constant trouble about having the latest batteries. They had to be pushed, matched, specially treated for even more voltage and I don't know what else. (Using LiPos nowadays, there's less trouble with the batteries but the drive train and the speed controllers but that's another story …) Thus, when starting Mini-Z racing I thought I had to solve the problem of treating the batteries well, too. But: How to charge and discharge was not a question of achieving best results in terms of power or run time. It turned out that this was not a real problem because you have enough of it anyway. And if not: Throw away your batteries and buy new ones. Nevertheless you have to charge your batteries and discharge them after running.
Charger
Primarily the equipment rather had to be cheap in my case. Scanning my RC military boxes in the basement I found an outdated Futaba CDR-5000 charger from my old days of racing 1/10 touring cars which could be recycled well. It can handle almost all of the “old” (non-LiXX) battery types in any kind of charging modes.
After searching the internet for some hours, I found the perfect charging parameters for AAA batteries: 1 Ampere charge current, Delta Peak around 5-10mV/Cell and 45°C cell temperature as a second cut-off parameter. To take the temperature of the batteries I attached the temperature sensor to an Atomic charging tray.
Discharger
To discharge after the run I also wanted to use my “old stuff”. Unfortunately my Much More CTX D2 that I found in the military box as well is only able to discharge at 5A linear (or 30A pulse) which might be a little bit too high for AAA cells. So I had to look for another tool which could balance (at least) four cells. Balancing in this case means to achieve the same level of discharge among all cells. Because we are talking about NiMH batteries we have to control the discharge cut-off voltage in order to avoid damage due to a total discharge. I could find two opportunities: A very simple discharging tray from Atomic. Small, simple lightweight, not too beautiful and quite expensive. Or a pretty cool Novak Smart Tray SE discharger. Okay, it's designed for Sub-C cells, quite heavy and relatively large but you can adjust the cut-off voltage. I bought two of these beauties on eBay: The first one for 1 Euro (no joke!) and the other one for 7 Euros. As I declared above, these dischargers aren't use anymore in 1/10 touring car scene which makes them quite affordable. To make the AAA fit into the battery clips of the Smart Tray, they had to lifted a little bit. This problem can be solved by an DIY aluminum bar as you can see on the pictures. Altogether I'm quite happy with my solution although it's not the most common way to treat AAA batteries.
Flo
