Introduction: Cheap Battery Replacement for Cordless Tools

I have a couple of neighbors who support themselves by salvage on bulk trash days. They frequently find cordless tools missing chargers or without working batteries. In the throwaway society we live in it's usually cheaper to buy a new tool set than replace a battery and charger. I can get some of those tools for free, since they have no scrap metal value.

There is a Harbor Freight store in the town I live in and I realized they were still selling NiCad packs separately for their Drill Master brand of tools. An 18v, 1.3 amp-hour nicad pack costs $13 by itself, and the charger is $7. HF is running a special now selling a drill kit with the battery and charger for $17. So if I can find a use for the battery and charger, HF will "pay" me $3 to take a drill off their hands.

I bought a set to experiment with.

Step 1: Getting the Battery Adapter

I made slide adapters for a 14.4v Craftsman drill and Milwaukee Sawzall by hand from scraps of plywood and metal I had laying around, but it was time consuming. I found an ebay seller who makes various adapters with a plastic duplicator and bought 4 of his adapters for about $12 each. There are many battery adapters out there. Most go from one brand to another, but I only want to use one brand of cheap battery on all my cordless tools for the sake of convenience and cost, so I got the HF adapter.

If you search for "cordless tool battery adapter" on ebay or Amazon, you will see the selection offered. Change the search to "drill master battery adapter" on eBay and you will get the one I bought.

Step 2: Testing the Battery With Tools

Since the tools were salvage and not necessarily intended for 18v operation, I used wire jumpers and the HF battery to make sure they would work. The 12v Craftsman drill was happy to run from 18v, but the 14.4v Craftsman drill had some water damage that required cleaning and oiling.

The Milwaukee Sawzall is an old-school beast, but it happily runs from a battery.

One thing you MUST be careful of is wiring polarity. Modern cordless tools with variable speed controls simply will not run or will short the battery if hooked up backwards. Making the wire connections to the adapter usually meant opening up the tool shell. That makes polarity checking easier. In every tool I opened, the red wire going to the battery was the + plus lead.

I used solder or crimp connectors to make the wire connections and common drywall screws or #6 threaded machine screws to attach the adapters to the base of the tool.

I also had a nice drill that shorted out the battery no matter how I hooked it up. That turned out to be a shorted diode, inserted as a safety quick stop in case you drop the trigger/tool. Replacing the diode allowed that drill to be used again.

In the end I now have a set of nice cordless tools that all run from a cheap easily replaceable battery.