How do I revive a NiMh pack?

Hi, guys

Summer is almost here and I am preparing my Traxxas Revo Nitro Truck for summer fun, while looking in the garage I found an old 3300 ma 7.2V battery pack that read 1.9V, totally dead! I have a MRC superbrain 969 charger and am currently giving it a few cycles to see if I can revive it, so far I've gotten 1000ma out of it, I am charging it at 1500ma and discharging it at 3000ma, but would like to know what is the best charge/discharge rate to revive it?

Thanks!
AlexGT

Hi Alex !

The currents sound reasonable.

But I would suggest treating the cells individually, to prevent the cells to diverge even more. (I know, might not really be feasonable with RC-Packs...) At least, try to check the voltage of each cell (charged as well as discharged) to determine if you have some really decreased cells.

There is some guy in Germany who really advocates the benefits of cycling NiHM cells with 0.5 to 1.5 C in terms of capacity and internal resistance.

(Link, sorry, only german: http://www.accu-select.de/http://www.accu-select.de/startseite.htm )

You will probably need up to 5 cycles to get the best results.

I usually trickle charge the battery for 12 hours or so, then discharge (around 1-2C), then charge around 0.5C, then move up to 1-2C rates for charging.

I'm not sure if this is a better method than yours, but it works for me.

Hello Alex,

I would start with a charge of 300 mA for 16 hours. Then you can go back to your cycling. The initial 16 hour charge is designed to balance the cells within the pack.

Tom

Thanks, so far so good! I got 2500ma on the last cycle, I am now giving it a slow charge at 200ma, I think its gonna live!

Thanks for your help
AlexGT