March 6, 2015, 11:21 a.m.

The Impossible Li-ion Battery

About three years ago I purchased a Makita LXT BHP452 hammer drill/driver. This is a cordless unit. I usually prefer cabled power tools simply because of my usage patterns. I use power tools very infrequently, and battery driven units are horrible for this type of usage. One would need to spend half an hour to an hour every couple of months when you want to use the drill, to charge it first. That would be a huge pain. So I never purchased cordless power tools, until now.

I am not using the drill much, in total I have drilled maybe 100 holes and screwed in about 200 screws. The craziness is that I have never charged the battery since I purchased this tool 3 years ago, when I performed an initial charge lasting about 20 minutes. The battery still has enough power to properly drill holes, and it is strong enough that I cannot hold down the chuck - there is still too much torque.

Knowing something about Li-ion batteries, you would realise that this defies physics. Li-ion batteries drain at a rate of approximately 8% per month at room temperature. Coupled with my infrequent usage, at best I'd expect to get 1 year of usage without charging up. It has been 36 months, i.e. this Li-ion battery cannot be draining faster than 2.6% per month. It is the BL1830 18V 3.0Ah Li-ion battery... Incredible.