I am going to move the battery to
the trunk and upgrade my alternator
to a 100amp tuff stuff alternator.
What gauge wire do I need to use
going to and from the disconnect
switch?

Run #6 in copper.

Thank you for the reply.

Wait a minute---let's look this over---

what kind of disconnect are you dreaming up?

I'm gonna guess you bought a "one wire" alternator, and if so, here's what you have-----

The alternator voltage sense is AT THE ALTERNATOR, so now? do I assume?? you are running a no6 all the way from the alternator TO THE BACK to the batt. side of the disconnect, then from the cold side of the disconect, you run a HEAVIER cable ALL THE WAY back up front where all the loads are connected?

If so, you have one hell of a lot of wire, there

You may find---if so---that you don't have decent voltage "up front" with the car running.

Doesn't sound good. Better read up on this topic at Mad Electric. It can point you in the right direction.

http://www.madelectrical.com/electrical-tech.shtml

Mopar alternators are terrible at producing power at low/ idle rpm, and not wiring them correctly to a rear mounted battery can make things worse.

I just finished upgrading my charging system with a CS144 alternator. It pretty much bolts right on and puts out up to 120 amps at idle, and maintains 14 volts at 850 rpm with both electric fans, my electric fuel pump and MSD running. Over 1000 rpm it holds 14.55 volts and is capable of supplying over 170 amps. I'll post a picture later.

Wire it up like this with the relay mounted up front. That way you don't need to run the 6 guage wire all the way to the back of the car and it will kill the power and engine when the emergancy shut off is pulled.

That is certainly one way. Make sure you actually get a "continuous duty" solenoid and not a starter solenoid. The latter won't last long---about 10 minutes!!

http://www.summitracing.com/parts/TFF-7509RFDP/
This is the alternator I have with a seperate
voltage regulator. I like the solenoid up front
idea and can run the electric fuel pump to the solenoid.
What gauge wire do I need for the trigger?
I will have a Ford type starter solenoid in the trunk,
so the battery cable will be dead other then when starting.

Thanks for all the info from everyone.

With the alternator you chose, all you need to do is break the ignition feed to the alternator, and you can do that with a smaller relay, and by using a 4 post disconnect

A 4 post disconnect has two large posts for the main battery feed, and two smaller ones.

You could, for example, put a general purpose relay up front near the regulator. Break the ign feed lead to the regulator, and put the relay Normally Open (NO) contacts in series.

Run two no 18's or 16's back with your cable to the trunk, hooked to the small posts on the solenoid.

Wire like this:

Starting at the point where you broke the ign feed to the regulator, hook one wire to the IGN side coming out of the bulkhead (ign run)

the wire goes back to the disconnect and back up front. Hook the other wire coming up front to your relay coil, and ground the coil.

In other words, with key on and disconnect on, the relay closes and feeds the regulator. If you either turn off the key OR the disconnect, the alternator stops charging.

Another way to do this would be to run two no 10's back to the disconnect (they may not need to be quite this big, but hey) and eliminate the relay.

In this case, hook the no 10s coming back to the small posts, and up front, once again, break the IGN RUN feed to the regulator. Hook the two no10s, one to each end of this break, and you're done.

(The reason you need either a relay or large wire for this to the rear, is this IS your battery voltage sensing lead, and now it's a "lot longer" than it used to be)

Thats exactly how I wired up mine. As stated before make sure you get a constant duty ford syle relay. I got mine at napa for about 30$. I don't see a problem with the diagram. When the disconnect is on woulnt you want the relay to come on and let the alt do it's job? When the disconnect is turned off it shuts off the relay and the power to the alt. Right?

My Cuda chassis car was wired that way for years and when you turned off the kill switch everything shut down. Maybe this won’t work with production wiring. I have only used it on race cars.

wire size ? 8 is MORE than enough... a 100 amps alt doesn't mean will out out full 100 amps, just it has the capacity. Will offer what car demands. Hard to believe your car will demand 100 amps.

How to wire it ?... use the same battery cable to the charge system

Originally, the charging wiring runs: alt-amm-starter relay-batt.

ond this system the starter motor gets the soruce on a dif parallel main batt wire where the battery terminal end gets spliced the main wire and the car system wire ( runing to the starter relay as a splice too )

you can run it: alt-amm-starter relay-starter motor

the main wire to starter motor will finish the circuit to the batt. The Main wire is used JUST on crankin moment. The rest of time will work as a bridge between batt and alt.

Of course splice the batt wire ( starter motor ) and the starter relay wire ( coming from the rest of system ) together on same terminal


In other words:

No need to run a diff wire between alt and batt, or amm and alt... simply use the same main batt wire to complete the circuit. The only diff will be the wire original set between starter relay and batt, will be now between starter relay and starter motor

still will be enough, since the max output will be just for some minutes

BTDT

That is gonna be a lot of heat for a few minutes depending on how undersized the wire is.

another detail: at idle the alt NEVER puts out the max capacity even with batt dead. The condition is not rev it up.

so 8 is still safe.

more than the wire itself is more important to keep an eye on the terminals health and tightness. Note: I'm not saying wire gauge is not important.

If you see stock diagrams, your find 6 gauge to feed starter motors, and they draw up to 200 amps... true is just for the cranking moment, but on a dead battery, at iddle will never get 100 amps and whatever it pus, will be not more than 5 minutes as much... then the output power will began to decrease.

also depends on the regulator conditions.

You can use 6 gauge if you want though, won't damage anything, just harder to handle and route it!