Look, it's taking voltage from 4 AA cells, at 1.2 to 1.4 volts each. The NiMH pack is fully capable of delivering enough amperage to utterly catch fire to the lighthead; at least 5 amps at the 5 volts or so. If I regulate a LiIon to 5 volts, there is simply no conceivable way that the lighthead could even know the difference, even if they designed it to try to tell.

I've done plenty of circuit design, including buck/boost regulators, and there is simply no accounting for what the guy at Dinotte said. He really got grouchy about it, and I just decided to heck with it, it's not worth arguing with this guy.