Black & Decker charger

[Dasypus]

Hi.  I left my BDC2 36v battery charger charging the battery and noticed after a while the Green LED was no longer lit.  The battery was fully charged.  On opening the charger I found that the 3.15A input fuse had blown, so got another and replaced it.  Now the fuse does not blow, but the LED does not light when the battery is inserted, as expected.  I am not an expert in electronics, and being very careful, noticing some 340V DC and AC being stepped down to around 42V which (I think) is the charging voltage for the BL20362 battery, and this appears at the battery charging terminals.  There is a PIC16F microcontroller on what appears to be LV side, but no DC voltages anywhere.  There are no visible signs of damage that I can see, including inside the battery itself (apart from a burning smell on my fingers after battery disassembly, but this may be due to overheating?).  I still can't tell if the charger is at fault, or the battery.  Does the LV side of the circuit get its power from the battery, I know that may sound silly, but it would explain why the LED does nothing until one is plugged in, or did when it was working).  I want to avoid messing too much inside due to the nasty voltages present (everything is also 115V above ground, double insulated device, etc...).  There is also a TOP264-271 power supply chip, and the HV circuit roughly follows the example given in its data sheet to the point where the 42V exists after a twin diode rectifier, and that's as far as my limited knowledge goes...  Regards.