Within the last year Harbor Freight has stopped selling nicad packs for their house brand of tools. I was buying their 18v battery and swapping the guts with the inside of failed Black and Decker HPB18 nicad packs. It was a perfect fit except for the wiring and less expensive. Plus there are Harbor Freight retail locations near me so I don't have to order and wait from eBay or Amazon.
Since they stopped selling nicad packs I wondered if I could do a lithium conversion to an HPB18.
The short answer is yes. For $20 plus tax HF sells an 18v lipo pack with charger under the Warrior name (their current house brand) That pack opens with a 0 phillips bit and the cells and board lift out as a unit without any further effort. If you remove the 4 middle risers in the bottom of the HPB18 shell the Warrior pack will fit upside down inside the HPB18 shell. Solder wires from the + and - terminals on the top of the HPB18 to the Warrior terminals and use the 2 remaining screws on the HPB18 shell plus some super glue to seal the pack. Drill a hole in the side end of the HPB18 shell for the charge plug you get with the Warrior pack and you now have a proper lithium conversion with battery balancing board and safeties.
The "warning" is about the safeties. On the second conversion I did I momentarily touched the + and - terminals on the Warrior pack. Very minor spark and no apparent damage. The charger still appeared to work. After sealing the converted pack I plugged it in to charge fully and it never did. I checked the voltage with the charger plugged in and saw the apparent pack voltage was way too high. Unplugged the charger and the pack voltage went to zero. Forced the case open and dissassembled the pack. Removed two 00 phillips screws holding the board and unsoldered the red and black balancing wires on one side and then I could plainly see one of the battery terminals was made as a fusible link. The pack is straight through to the terminals with no triacs on the negative side as is how most 18/20v lipo packs are made. There has to be a fuse for safety and it is a one-time fusible link. I blew mine with a momentary short that in my opinion should not have done that. No proper way to fix that, either. Not wanting to toss the pack I tinned both uprights of the H bridge and laid a small tinned stranded wire across to replace the blown bridge. Now the battery works again, took a full charge, but has no verifyable internal fuse.
The charger alone is worth the purchase. I have been fixing orphanned tools and a low current voltage regulated charger is required for the set of tool/battery/charger. Battery packs are easy enough to do.
