Behind this long title, I will simply tell you how to fix charging problem with Black & Decker cordless drills.
In my home toolbox, there was a broken cordless drill that had some battery issues. The engine-tool had not been used for a while, so the two 14.4V batteries were totally discharged, in a state called “deep-discharge”.
The problem was I can’t charge these batteries anymore: when I plugged the batteries onto the charger, the red led that indicates the battery isn’t charged yet light up for 1 second, and then, the green one light up…
So my first thought was something is going wrong inside the charger. I noticed several time (when all was working) that the battery charger was really hot.
The first defy was to open the shell of it. It was really painful, because Black&Decker uses some of these hex screws called “security torx”, with a cylinder in the middle:
The second problem with these screws are that two of them are in a tiny hole, and most of screwdrivers haven’t the right diameter to enter in.
The solution is a bit “Mac-Gyver approved”: I took another drill with a metal bit, and tried to break the head of the screw. Finally, I was able to open the box: the heat was so high that the plastic around the screw melted.
A first look on the circuit-board, and I found the issue: the charging resistor has been un-solded because it was to warm during previous charging. It is the big grey one, annoted “R2” on the board.
After fixing it, I simply closed back the charger and tried to charge my two batteries. Unfortunately, I had the same problem: red led for 1 sec, then green led.
After some research, I understood that the two batteries was to low to be able to charge (checked with the multimeter). For this drill-charger, the voltage of the battery must be higher than 7V. Mine was under 1V, so it needed to be boosted before charging…
On Catmacey’s blog, I found a similar charger story about a Black&Decker drill, followed by a little guide that explains how to revive NiCd batteries with a throwable camera with flash, and a Youtube video from dial2fast.
Moreover, this is another complete how-to using a throw-able camera trick.
It allowed me to go over the 7V needed by the charger. “In fine”, the red led charging lighted up until the complete charge of the battery. My drill was working back then!