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Black & Decker 18 volt charger not working

I have three Black and Decker, 18volt battery chargers, for the FireStorm series tools.

One is an orange dual charger.
One is the single black charger that came with the drill.
And one is the Radio charger.

The radio charger AC adapter case melted and no longer works.
The single and double chargers both seem to kill batteries, and do not charge.
I have voltage coming from the chargers, but I don't remember how much.

Does anyone know what the voltage should be on the charger?
More importantly, how do I repair the charger to output the correct voltage/current?