We just got some new Sennheiser wireless mics and they use AA batteries, unlike the old ones that use 9 volts. We're thinking about using rechargeable batteries. Are there any "gotchas"? If not, can anyone reccommend a good multi-format charger. I'm looking at NiMH batteries as we've had a great experience with NiMH NPs on our camcorder.
Most rechargeable batteries won't provide an adequate voltage for use in transmitters and other devices. Some will provide a satisfactory initial voltage and then rapidly lose it, requiring frequent changes.
Also, and most important to pro audio, is the "curve" of the voltage falloff. Alkaline and Lithium batts provide a fairly constant voltage over a period of time and then slowly lose voltage until the device indicates the low-voltage or shuts down.
Rechargeable batts have a different curve, they will provide a high initial voltage and almost immediately, but gradually, begin to lose it. The "gotcha" is that they will lose the ability to operate a device almost as soon as the device indicates a low voltage. That's why most soundmen don't use them for critical applications. I think they would be fine for walkie-talkies or flashlights.
Rechargeable battery technology may have improved in the last few years, however. If anyone knows of any news on this -please post.