Upgrading an old cordless drill from NiCd to Lithium battery using 18650 cells
Channel: Reid Allaway
Date: 2020-08-18

A quick, as in hastily-produced, video showing some of the rudiments and maybe a few details of one approach to getting good cordless drills back in service by gutting their old NiCd or NiMH battery packs and shoehorning some 18650 lithium ion cells in their place.

There are a bunch of other videos on rebuilding NiCd packs for old favourite Makitas and the like but just putting new NiCd cells back in seems crazy to me now that lithium ion cells are ubiquitous and cheap.

A couple of the things I did not address, really at all, in this video include:
1. charging.  You need a charger or power supply that will charge at constant current (CC) until a target terminal voltage is attained and then switch to constant voltage (CV) with current gradually dropping to zero.  This is how lithium likes to be charged and you have to figure out how to do it.  A cheap little adjustable DC-DC converter that provides CC-CV behaviour is the most accessible solutions.  A balance charger for the RC market (such as the ubiquitous imax B6) might be another good tool as it allows you to test your cells and balance them.

2. choosing your cells A:  Be sure to test and select cells that maintain balance and have similar capacity.  Run several test cycles to be sure or use a BMS.  Look elsewhere for info on how to do all of this.

3. choosing your cells B:  you want high drain or "power cells" vs "standard" low current 18650s.  You need cells salvaged from power tool batteries rather than from laptops.  They must be capable of delivering many amps (say 30) for short periods to get the motor spinning from a start and to handle high loads.