I like to pick up early vintage cordless drills at thrift stores, they go for cheap especially if it has no charger and a dead battery, this vintage Sears 7.2 volt nicad tool went for $2 because it was the latter. I had on hand a T-Plug 11.1V 1500mAh 25C 3S VOK Discharge LiPO Battery that runs for about $8 U.S., including shipping, and decided to use it for the hack. I’ve found from past conversions that the voltage disparity isn’t much of an issue, the D.C. motors used in these products are pretty robust and can stand a wide margin of abuse and still live a long life.
The contents of the following Instructable represent the experiences and outcome of the author, no guarantee is made as to suitability of the repetition of the information presented, therefore careful study should be undertaken by those wishing to duplicate these results, including a self- assessment of prerequisite skills, knowledge, and understanding of the subject matter.
Step 1: Tear Down to Build Up
The first step is to remove the defunct NiCad cells and clean up the contacts and the housing that transfer battery power to the drill. I soaked and scrubbed them in vinegar to dissolve acid and corrosion, then rinsed well to neutralize them. A test fit confirmed that little more need be done to incorporate the new battery into the build.
Step 2: Route Power
I soldered a couple of 18 gauge wires to the contacts as down-leads to connect with the Lipo cells via a pair of insulated screw terminals instead of soldering them together, this would allow for easy replacement if it became necessary.
Step 3: Final Thoughts
The only case modification I made was to provide the balance charger connector a feed-through hole to allow hookup to my charger, and by using a salvaged set of contacts, I can easily recharge and balance the battery without any issues whatsoever. The weight decrease is remarkable and the output power is fantastic, so for $10 U.S. it’s a deal for me.