I have a board that drives three bistable relays for turning on/off three 12V loads.
To switch the relays, the board provides 6 outputs that connects a battery-negative pulse of 150ms at a maximum power rating of 10W at 12V. Each of these outputs drives one of the two coils (either on/off) of one of the 3 relays.
However the relays require a 150ms pulse of 36W at 12V, which is too much for the board to handle.
I plan to get 6 MOSFETs to increase the power rating of these outputs. I will connect each MOSFET gate pin to a board output, the source to the battery positive. This way, when the board attempts to switch a relay, it will apply a voltage between the gate and the source and turn the MOSFET on. The drain pin of the MOSFET goes to the relay coil (the other side being connected to the battery negative).
I think I need N-channel MOSFETs with a minimum voltage gate-source threshold (VGSTH) of ~10V and a maximum drain-source voltage of at least 15V. Considering how brief and infrequent the pulse will be I don't think the other specs really matter, but ideally the drain/source resistance when on (RDS-on) of as low as possible.
Will this work? Am I speccing the MOSFETs needed correctly?