While this tutorial isn't groundbreaking, it may give you the motivation you need to get your broken cordless tools back up and running.
Harbor Freight and I have a Loove hate relationship. Half of the stuff they sell is inexpensive and worthwhile, the other half is inexpensive and junky. If you shop there, you know what I'm talking about.
Some of the junkiest items they sell are the cordless power tools. 9 times out of 10, the batteries die quickly or were never good to begin with. Sometimes its the fault of the charger or AC adapter, sometimes it's the "rechargeable" batteries. In any case, they aren't worth picking up unless you're in the mood to gamble.
If you have by chance made the mistake of buying one (like i did) and can no longer use the battery for whatever reason- read Step one.
-Cordless 18-24v Power tool (I used a circular saw)
-2 short strands of wire (I forget what gauge I used but most should be fine)
-1/4th inch male and female audio jacks
-18-24v 2A Power Supply (I used a salvaged epson printer power supply rated 24v, 2A)
-drill / bits
-screwdrivers (one philips, one flathead)
-solder / soldering iron
Pry it open GENTLY with a flathead screwdriver. Take the batteries and contacts out (they will be attatched)
now bend or cut the leads off the top batteries, but leave some metal to the battery contacts, you need enough to solder wire onto them.
remove the regargeable cells. (then recycle them if you have the means)
Now, Hot glue the contacts into place so they'll stay put. Be sure not to get much hot glue on the bottom parts of them, you need to solder wire there.
Drill a hole in the bottom of the battery to fit the 1/4th inch jack.
Insert the 1/4th inch jack then solder the two wires to each lead. Make note of the polarity (+ / - ).
I used hot glue to fasten it in.
Put the contacts back into the tip of the battery and re-assemble your battery.
Be sure to make sure the polarity is correct, just put + to + and - to -
If you get it wrong, it should be ok, the tool will probably just spin backwards.
(Just swap the wires on this tip so you dont have to open your battery again.)
I used a male jack with a screw on plastic shield and held it in place with some hot glue.
(there's a different picture in the intro)
Note- it may take (literally) a second or two for things to start spinning because the AC adapter needs to charge up. no biggie 4 me.