> However, be very carefull not to exceed Vgs(max) which is often in
> the 10-12v range.  Carefull selection of the two resistors shown in
> your schematic connected to the gate will limit the maximum gate voltage.
> 
> HTH

Yes, it do

So, with a good battery and no signal from the PIC, source will have
13.5V on it, and 13.5 on the gate, Vgs = 0V. Then the gate should not
go below 1.5V to keep Vgs >= 12V (assuming 12V limit) ?

The pdf for the IRF5800TR says Vgs of +/- 20V. It also has a diagram
(Fig 12) showing Ron vs Vgs. Lowest Ron is at Vgs of 15V, and that's
only a little lower than Vgs = 12V

>From those figures then, would it be correct that the gate on this FET
can safely be pulled up with a gate resistor to B+ and pulled to ground
with the PIC ?

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