Note that the IRF2804PBF is an N-MOSFET so it needs to be wired upside down from the circuit you show in post #7 [gate to (+) line, drain to (-) power, and source to (-) inverter connection].

 

Note that the IRF2804PBF is an N-MOSFET so it needs to be wired upside down from the circuit you show in post #7 [gate to (+) line, drain to (-) power, and source to (-) inverter connection].

Bummer. I just now finished this Visio drawing. You are saying that it is incorrect here.
If I reverse the source and drain, essentially a vertical mirror, then it will be correct?

 

Note that the IRF2804PBF is an N-MOSFET so it needs to be wired upside down from the circuit you show in post #7 [gate to (+) line, drain to (-) power, and source to (-) inverter connection].

Okay. Would the following be correct?

 

No. You are showing P-MOSFETs.
Here is the correct schematic.

 

Why dont you use a simple Contactor with a Diode that energises only on the correct polarity?

 

No. You are showing P-MOSFETs.
Here is the correct schematic.

View attachment 105544

THANK YOU! FANTASTIC!
Thanks for doing this. I think I can take it from here.
Photos of final product when complete. Don't hold your breath, I have some other work to get done first around here.

Ed

 

Why dont you use a simple Contactor with a Diode that energises only on the correct polarity?

Have you priced an 80 amp, continuous duty "simple Contactor"?

 

Have you priced an 80 amp, continuous duty "simple Contactor"?

Have you seen how simple the setup is ?

http://www.ebay.com/itm/DC-Car-Vehi...ash=item3ab3bb7466:g:JGUAAOSwYHxWHOZu&vxp=mtr

 

Not much simpler than one or two MOSFETs.
And you buy at your own risk on fleabay.

 

No. You are showing P-MOSFETs.
Here is the correct schematic.

View attachment 105544

Hi crutschow, Can I expect any significant current through the gate? My guess is that I won't, but I thought I'd check before I start wiring things up.

I ordered the MOSFET's but they are on backorder -- with no expected delevery date, so I guess I won't get to this very soon.

Ed

 

Hi crutschow, Can I expect any significant current through the gate? My guess is that I won't, but I thought I'd check before I start wiring things up.
.................

A MOSFET gate looks like a capacitor, so the current is essentially zero, only a very small leakage current as given in the data sheet (200nA for the IRF2804PBF.)

 

A MOSFET gate looks like a capacitor, so the current is essentially zero, only a very small leakage current as given in the data sheet (200nA for the IRF2804PBF.)

That makes sense to me. Thanks.

MOSFETs have been shipped! I already have the heatsinks, wire, fuse/fuse holder, so I'll be able to make my "idiot-proof" cable (with battery clamps) shortly.

crutschow...before I make this... can you please take a look at the following schematic and "strategy" for making this cable? I'm no good at 3-d drawings or any kind of artistic rendering, so I can only explain here: if I put the MOSFETs in line but up-side-down from each other, I can easily make something that will have balanced wire lengths in case that is important for this. Here is the schematic and the "strategy" for connecting the MOSFETs:

 

That layout with the back-to-back connections looks fine to me.
Equal cable lengths is of no particular consequence for this DC circuit.