How to Fix a Broken Cordless Drill Charger

Step 1 Verify what the problem is

This Instructable assumes that you identify that the problem is the charger itself.  In my case, a 15v power supply to charge 12v batteries was pumping out 3v.  Get a simple multimeter and measure the voltage at the terminals of the charger.   If the voltage is less than the rated voltage, then this Instructable might be for you!

Comments

[ironsmiter]

Since this is a VERY dumb charger...

You'll want to drop that current to around 1/10C(putting in 1/10th of the total charge per hour)
Probably the simplist way to do it, without changing out your powersupply, is to solder in a current limiting resistor.

Not SURE, since the picture is a bit small, but there APPEARS to be one already on that tiny board. you SHOULD just need to upgrade it, to handle the 800mA powerbrick, vs the old 200mA brick

Or am I completely off base, and that's the resistor for the LED light?
If so, slap the current limiting resistor right on the power line coming frim the wallwart.

12 volt NiCd... should be around 2000mAh pack when new. especially judging by the original power supply.
Someone double check my math, but i think a 15Ohm, 1 watt resistor should do nicely. even a 1/2 watt SHOULD work. but calculated "need" is for a 0.6 watt resistor.