That drill is the exception rather than the rule.
I have had it nearly 6 years and its the first one I have actually managed to wear out.
Bigger drill I replace roughly every year as the batteries are either unobtanium or cost more than a new drill.
This is a particularly good one and as I have found a source of solder tagged AA lipos im rebuilding the packs.
Taking a few apart has shown some plain whacky charging circuits.
What I cannot understand is why someone has not come up with a one chip solution for balanced charging.