cordless drill charger

I was thinking about the battery being shorted...but not tried another battery yet....this is about the 3 rd charger I seen with this problem....they get so hot it melts the plastic....maybe they are only made to last so long......thanks for your response

After a few law suites over cordless drill charging units causing fires some manufacturers have intentionally made the chargers lightweight so that they will fail before any possibility of creating a fire.

Replacement chargers that will not burn out, or get hot so easily are available on e-bay.

The B&D cordless I have can't get hot as it has a thermal fuse bound into the transformer primary - or at least it did until the pack developed a couple of shorted cells (normal for B&D!) although they do run warmer than you might expect in normal operation.

You can easily tell if it has shorted cells as the transformer primary goes O/C and stays stone cold when plugged in.

Does the charger overheat when plugged into the AC power but no battery plugged into the charger?

H. R. (Bob) Hofmann

It does not over heat without the battery plugged in....which makes it look like no load no overheat

What is the nominal voltage of the battery pack? Have you measured the open citrcuit voltage of the battery pack, ie just sitting on the bench?

H. R. Hofmann

Does anyone know what the value is of the Thermal Fuse in the Black and Decker charger? I'm looking to replace mine. It's for an 18V charger model PS1518bu.

All the one's I've seen (though not so far an 18V) have the thermal fuse bound tightly onto the surface of the primary winding and is almost impossible to cut away without damaging said winding.

Usually the voltage and VA rating is marked on the wall-wart part of the charger, so raid the junk box for a replacement with the same ratings - I used a Hayes modem transformer to repair the 12V charger and an ex printer wall-wart for the 14.4V drill.

Once you've replaced the O/C transformer, open the cradle section of the charger and check for a limiting resistor along with the 4 diodes, if you still have shorted cells the resistor will overheat, discolour and possibly change value - making it difficult to find the correct replacement, as it is you may have to make a "best guess" if the resistor is already discoloured and the value drifted.

If you plan to attempt unsticking the shorted cells, temporarily replace the limiting resistor with a 10W WW and connect the partly dismantled pack to the charger with fly-leads. Unsticking current is supplied by parallel connected H4 bulb filaments from a 12V SLA battery - some cells might be a bit stubborn, if so short the H4 filaments for unlimited current but only flick the wire on!

Take very great care to only apply the unsticking current with the correct polarity for each cell in turn or the short will become permanent!

As for buying new batteries, last time I checked B&D were charging so much for replacements that I could have bought 2 new better spec drills for what B&D were charging for 1 battery! The 14.4V drill was new - I already knew better than buy anything else from B&D when I found the 12V drill left out by the bins (usual fault - S/C cells & O/C transformer). Next time they pack up, I buy a different brand that isn't expensive crap like B&D!