Charging a flashlight while using it?

On my bike, i use a one 4.2 lithium battery LED flashlight. Very useful, because
-i can charge it on the hub-dynamo,
-i can have it ON continously when in the city, so been visible even when the bike stops,
-i can use it off the bike as an ordinary light source.

The question:
Is it any bad (for the battery apparently) if i have it connected to charge while riding and having it ON?

If it is OK, then it is exellent news, because you can use it non-stop on long night rides. :duh2:

Oh, by the way, and what about NiMH batteries?

In general, I would say that it's not a problem to charge it while it is being used, but... it really depends on the circuit that is controlling the charge regulation for the battery. Lithium batteries are rather particular about not tolerating overcharge, as well as not tolerating regular charging at cold temperatures or when the battery has been discharged below a certain level.

NiMH batteries are much less demanding in regards to charge regulation. They won't catch on fire if overcharged, which is a nice feature.

Thanks for the good news, Steve.

Overcharging is no problem because the battery has it already by itself, overdischarging is relatively manageable (keeping an eye on the light, and learning by experience), hence the good news.

Or if you want to play hard, charge a second battery.

I assume you are just sending power into the USB charging port of the light? If it will let you turn it on while charging from a USB power source, it's probably not a problem.... but what do I know? I always recommend asking the manufacturer if it is okay or not.

Well, phew, it is a really cheap thing anyway, so my demands are not high. I just tinkered with it heavily, changing the LED, omitting the control board, those kind of things that make a tinkerer crazy, you know. It accepts 4.2V power to charge through a jack, and charges well with a *regulated* 5V from the hub-dynamo. Having been used for experimenting so heavily i do not think it would be wise to ask the manufacturer anyway. :nana: