I am attempting to use a N-Channel Logic Level MOSFET as a switch for a phone charger that runs on a 42V battery.
I have a resistor circuit with an LDR that currently outputs 3.3v when LIT with a torch and 0v when completely dark. Daylight outputs around 0.7V. The circuit works as expected for a few uses and then the MOSFET fails short and is now always on permanently (even when removed).
My Guess: Could the load (5V Step Down Regulator/Phone Charger) be inductive, similar to a relay and need a flyback diode somewhere? Placing one on +/- of the charger has no effect on longevity, as well as one on the main +/- of the battery.
The current of the charger should be less than 200ma at 42V for a 5W charger. Could it be higher at startup (it's rated for 30A).
They seem to fail when it is switched on/off more frequently.
MOSFETs can be placed in parallel to split the load, would this help?
I have killed more than 10 MOSFETs so far trying different combinations