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.