Help with charging/discharging NiMH batteries with imax b6ac

Hello - I recently purchased 2 nimh battery packs (6.0 V, 900 mAh, 5x1 AAA) and they have been really weird and I am wondering if I am setting up the charge/discharge correctly. Basically I hook the batteries up to my pololu 12 channel, and they die within minutes. What would be proper settings to charge and discharge each pack? So far I have tried charging at .9A, and discharging at 1C to 1V. Thanks.

Make sure your discharge only goes to 1v/cell, so in your case 5v. Beyond that I’m not sure what the problem might be, your charge/discharge setting sound fine. What is the voltage on the pack once it comes off of the charger?

Does the charger support cycling? If so, I’d suggest putting it on for 5-6 cycles to break the pack in.

I’m using the imax b6ac charger. The pack will read over 7 volts after charge, yet die so quick. I don’t understand.

What are recommended settings for discharge? Is there a formaul for what C to use depending on the battery?


I am sorry you are having problems with your battery packs. It sounds like you are using the battery pack with a Maestro; if that is correct, what do you have connected to the Maestro and do you know how much power it is drawing?

I agree with mapman, you will want to discharge to 1V per cell (i.e. 5V for your 5-cell battery packs). Additionally, 1C seems like a pretty high discharge rate. In general, you might try to avoid discharging at a rate over 0.5C (the lower the better).

- Zeeshan

The Wikipedia entry on AA NiMH batteries seems pretty complete and reliable … de_battery.

As others have noted, the entry warns not to discharge AA batteries to less than 1.0 V per cell. What can happen in a battery pack is voltage reversal for one or more cells, which destroys them. To test for that possibility you have to take the pack apart and separately charge up and discharge each battery. I’ve done this with a single-cell battery holder, using a 100 ohm resistor as the load. It will quickly become obvious if individual cells are bad.