I have a battery pack, made from 6 aaa nimh batteries. I installed it in my 1/16 kubelwagen. everytime I charge it, it will take about 300mah, then I was pormpt it is full charged( I have a triton charger). I measure the voltage is about 9v. but the car does not run as long as before. about 2 minute running. I measure it again, about 8V. redo the charging, take another 200mah. then stoped.
anybody know what is going on here?

Hello Tom

Although I can not answer your situation directly, I have experienced this with the 7.2V racing batteries of NiMH type. The issue that may be causing this is a false peak charge that the charger is stopping before it is fully charged. For NiMH batteries there are two such peaks to overcome. One is detected by the negative delta method and the second by another means that I can not recall at the moment. Once I replaced my charger with a new one the problem of partial capacity charging went away.

Also as a note, some of the chargers are not designed for smaller mah batteries as these are generally charged at a lower current rate. Quick charging a small mah battery may cause damage. Also the charging characteristics for the smaller mah battery may trip the charger into believing the peak has been obtained.

If you can 'hard charge' the battery with a dumb charger (without automatic electronic control) this may alleviate the problem, or at least verify if the charger settings need adjustment for this type battery.

Cheers
Eric Scott

thank you for the help.
The story is like this:
Originally, I can charge the battery pack about 1000mah. it will run very good in 10 minutes because the Kubelwagen is not heavy and ESC is strong enough to push it.
Just recently, I charge the battery either at 1A or 0.1A, it will only take about 200mah charge, then stoped. It took 1100mah charge last night.
but the battery look just does not have enough juice to push the car. I measured the Voltage, it is 8.9V. what I do not understand is, why the voltage is high, but not strong enough to push a little car. the esc is Futaba 230 with reverse.

Here you go. You "killed" your little batterys. But to test try a diffrent pack or try that pack on another ESC.I have had that model ESC and it will run a large truck/tank

how did I kill them?

Remember Tom

Measure the voltage under load. Measuring the battery without the motors running is deceiving, even residual charge can show full voltage. Try measuring the voltage when the motors are running.

Also note that the current delivery of the battery has a function as to the output current available per time (mah) i.e. a low mah battery is not ideal for continous motor loads, the occasional servo would be OK.

Cheers
Eric Scott

thank you Eric,
I will try to measure it under load. will let you know. thanks,tom

it is very strange, the battery seems playing with me.
when it is under load, the voltage drop to 5.0 V very quickly. when it has no load, the voltage increase back to 8.3V. so the charger always think it is fuly charged. the battery are NIMH 1400mah flat pack.
any idea to restore them?

The 3 A's where not ment to be ran with ESC/car you have.AKA you had to littler batterys for you RC and it sucked the life out of them LOL.I tryed the AA's in large trucks thay would run ok for a time or two then do more or less what yours have done.

Hello Tom

Just as I thought, the battery pack you are using does not have the current demand capability to drive motor loads (or other high current loads) continuously. Try a larger cell battery pack. Hint: The cell size A, B, C, D etc will give a rough idea of the current demand capability the pack can deliver. Generally speaking, the larger the cell, the more current demand it can deliver.

All may not be lost for your AA battery pack though, it may take a charge and used for low power electronics like a transistor radio, receiver or transmitter for instance.

Cheers
Eric Scott