The gate voltage sounds correct. It will jump up to the gate threshold and stay there until the controller caps charge, then jump up to 12v. Version with the switch should be fine as long as the switch is off when the battery is connected.
When FETs blow, it's quite typical that all the leads short together. That's normal.
Dang, about the only other thing I can think of is you got some bad FETs. That's very rare, but not impossible.
When FETs blow, it's quite typical that all the leads short together. That's normal.
Dang, about the only other thing I can think of is you got some bad FETs. That's very rare, but not impossible.