replacing built-in batteries?

[ixfd64]

I've noticed that many "rechargeable" flashlights use built-in batteries. However, there are two major disadvantages with built-in cells:

1. When the electricity runs out, you have no choice but wait for the battery to recharge.
2. The battery will eventually wear out, and the flashlight would be essentially dead.

I know that replacing built-in batteries usually isn't worth the hassle, but has anyone here ever done it?

 

[alpg88]

yes i did it, and i'm sure others here did so as well.
there are few things you have to watch out for, like charging current, charging time(in case of timed charging,). when installing larger pack.
but other that that all pretty much straight forward,

if you really worried of batteries being dead when you need it, you can install, a jack with a diode, after battery, before the bulb, and have "emergency" access you can hook up external power source, i did it once, worked fine, i tested it, but never had to use it, i don't bother doing it again.