NimH batteries are much better than the obsolete NiCads. You don't have to deplete the batteries before recharging, so no memory effect. Lion or Li-Po would be even better, but you would have to rig some system to hold it in place in the battery compartment since it would likely be smaller. And you need a pack with standard Tamiya plugs. If you have R/C gear you probably already have the compatible batteries and the charger.
Picked up a gently used Command Controller recently from a forum member and put in two new NimH battery packs. Used it at a launch 10 days ago. Worked great!
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I also sliced off a piece of the safety key so it would fit in the ignitor storage compartment. I always seem to lose those things:
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