The problem with NiMH is that lots of cheap devices are designed to run at 1.5 volts, and have dim lights or sluggish movement when used with 1.2 volt cells. I

The problem with NiMH is that lots of cheap devices are designed to run at 1.5 volts, and have dim lights or sluggish movement when used with 1.2 volt cells. It'd be nice if there were a voltage regulator product that could fit into a standard battery compartment. One option I've considered is to replace 2AA/2AAA with Li-Ion plus a dummy cell. But Li-Ion is around 4.2 volts fully charged, which might be too much.