Build an Endless Battery Adapter for Your Cordless Tools

If you have owned your tools for awhile you probably have at least one battery that will not hold a charge. If not you can check ebay, craigslist and the flee market for a used one. I have 18volt DeWalt tools. Your battery maybe slightly different, but the basics should be the same.

Remove the screws holding the battery housing together. Separate the housing and remove the battery pack. The connector that pugs into the tools was attached right to the battery pack. One end of the connector was soldered to the pack and the other has a short wire. Carefully remove the connector.

Decide what type of plug you want to use for your cord. You can use the type from an RC car, CB, cigarette lighter, etc. I used a standard 110v plug because I had it on hand and I will remember not plug it into the wall.
Drill a hole on the bottom of the battery housing and feed the wires for your plug through the hole. Tie a knot in the wires to prevent them from pulling out. Solder one wire to the tab on the connector. Be careful not to overheat it and melt the plastic. It will stick easily if you tin the wire first. You can solder or crimp the other wires together. Make sure you check the polarity with a meter.

The connector was held into the housing by the battery pack. Since the battery pack is not going back into the housing I needed a way to secure the connector in place. I drilled a pilot hole and inserted a screw. I cut off the head of the screw and filed it flush. I thought about about glue or epoxy, but the screws were right on the table, so I used one. Reassemble the battery housing.

I used about 15' of power cord and crimped a pair of battery clips to the other end of the cord. I considered using a cigarette plug instead of battery clips, but decided against it because some vehicles have under sized wires and fuses. Now I can go right to the battery of any vehicle or portable power supply (jumper pack). Install a 30 amp fuse for safety.

An alternator puts out about 14.5 volts. A 12 volt tool should be fine on 14 volts. I would becareful using 9.6 volt tools. They will work, but make sure they do not over heat. DC motors can run at a higher voltage. My 18 volt tools are a little underpowered on 14 volts, but they still run. I do not have to stop working while I wait for a battery to recharge. The adapter will fit all of my tools. There are no modifications to the tools.

I use this cord and adapter to run my drill when I pump waste vegetable oil (see my other articles). A battery would last about 20 gallons. Now I can just keep running the drill and there's no inverter to fool with.