WARNING: PERFORMING THIS MOD WILL PROBABLY COMPLETELY VOID ANY WARRANTY YOU MAY HAVE.

You may notice the charger included with Harbor Freight rechargeable drills (at least the Drill Master 66965) is not a "float" charger, meaning you CAN NOT leave the battery on the charger for too long otherwise you will destroy the battery.

This Instructable fixes this issue.

This limits the charging current to approximately 100 milliamps which is less than 10 % of the 1200 milliamp rating of the battery thus OK for a constant “FLOAT” charger. Note - Allow no less than 14 hours for full recharge of a fully discharged battery but you may leave ON after that time.

Step 1: Open the Charger

Turn the charger base over. There are 4 screws. Take them out. Remove bottom of charger.

Step 2: Make Your Resistor

Take 3 Radio Shack 10 ohm/ 1 watt resistors (Radio Shack # 271-151, BUY 2 PACKS) clip them short, and solder them in series.
(yes, I know my soldering STINKS.) Cut a piece of shrink tubing to cover the resistor and heat to shrink around it.

Step 3: Insert Resistor Into Charger Base and Close

Clip red wire in the charger. Strip the covering to expose appx 1/4" of the wire on each.
My pictures aren't great but I forgot to add shrink tubing to one end to cover the solder connection.
Shove it in and replace the cover.

This limits the charging current to approximately 100 milliamps which is less than 10 % of the 1200 milliamp rating of the battery thus OK for a constant “FLOAT” charger. Note - Allow no less than 14 hours for full recharge of a fully discharged battery but you may leave ON after that time.