simple inverter reverse polarity protection cable project

crutschow

Joined Mar 14, 2008
24,424
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].
 

Thread Starter

edro

Joined May 5, 2016
16
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?
 
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Thread Starter

edro

Joined May 5, 2016
16
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
 

crutschow

Joined Mar 14, 2008
24,424
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.)
 

Thread Starter

edro

Joined May 5, 2016
16
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:

reverse polarity protection MOSFET circuit v6.jpg

reverse polarity protection MOSFET strategy v6.jpg
 

crutschow

Joined Mar 14, 2008
24,424
That layout with the back-to-back connections looks fine to me.
Equal cable lengths is of no particular consequence for this DC circuit.
 
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