Battery Relocation

[dusterman440]

It's currently an all stock wiring 67' Valiant. I'm working on a battery relocation to the trunk and I'm looking to run this idea by someone else to make sure I'm not missing something. I need it to be able to pass NHRA tech (disconnect shuts down the engine), but I also would like the starter (B+) circuit to only be hot when starting, and I'd like the hot wire from the alternator to be killed if the disconnect is flipped so that the only hot wires are in the trunk when disconnect is flipped.

Diagram is a bit crude and simplistic, but this is what I'm thinking.

 

[67Dart273]

I'm pretty opinionated about all this. First, why is it so important to have the starter dead? When was the last time one of those cables shorted? (And if it does you have a disconnect!!) You STILL need a HEAVY cable for the alternator and to feed power to the car. Just reconsider

But if you don't, I believe that "one wire" alternators are as much trouble as they avoid. If you use a "3 wire" or such, you can kill the field wiring and kill the output, and it is no longer a problem

another issue with "one" wire units is that because the v sensing is also on the one wire, they must have a MUCH larger charge wire than the same amp "3 wire" units.

Use a good quality FOUR terminal disconnect. Use the auxiliary terminals to kill something (even with a relay) that will kill the ignition/ compulter (if EFI) etc. You MUST wire this up in such a way that the alternator does not keep the engine running

 

[Syleng1]

David Frieburger did a whole episode on Road Kill about this on his old ford t.
Somewhere he must have a t shirt for sale with the diagram on it.

 

[Bewy]

Not sure why you would even bother relocating the bat. You are adding more weight because you now have to run a thick [ to minimise voltage drop over the long distance ] copper cable from bat to starter. Copper is heavy. You can use alum, but it has to be thicker because it has more resistance....

As for the extra weight over the rear wheels. Calculate the rear end weight proportion & you will find the extra bat weight is insignificant.

 

[Heywodja]

@crackedback He hooked me up with my setup, he knows his stuf!

 

[Mattax]

I'd like the hot wire from the alternator to be killed if the disconnect is flipped

Read the explanation of how alternators work in the Identifying Chrysler Alternators thread.
The alternator will not be capable of supplying power if the rotor can't get electricity, or if the ignition is cut and the engine stops.

One method is diagramed here.

Del, Is this what you are saying? Use the original 'run' feed to control a relay, and power the ignition etc through the relay?

The alternator output could also go direct to the relay.

questions about battery disconnect wiring
The methods discussed there avoid the need for a high current continuous duty relay.
If you like that, but also want the starter cable killed, that's discussed too.

There is also discussion and photos on how to disconnect the heavy cable to the starter in that thread and others.

Rob posted his schematic in post #24 of questions about battery disconnect wiring

...

It keeps the big cable to the starter off. Only when the key switch goes to start does the solenoid get the power to connect it to the battery cable.
This is basically @crackedback's schematic - I just moved things around so it was easier for me to read.

 

[mopowers]

Not sure why you would even bother relocating the bat. You are adding more weight because you now have to run a thick [ to minimise voltage drop over the long distance ] copper cable from bat to starter. Copper is heavy. You can use alum, but it has to be thicker because it has more resistance....

As for the extra weight over the rear wheels. Calculate the rear end weight proportion & you will find the extra bat weight is insignificant.

Do you even read what you type? Moving the weight of the battery to the rear is insignificant, but the extra 5 or so lbs of battery cable is???

 

[crackedback]

Do you even read what you type? Moving the weight of the battery to the rear is insignificant, but the extra 5 or so lbs of battery cable is???

Reminds me of the car we had that ran faster with 2 batteries in the trunk than one. That battery weight sure slowed it down.

 

[Bewy]

Mopowers.

Yes I DO read what I type. Maybe you should learn to read better....

Did you see the bit about: rear end weight proportion....which will be several hundred pounds. A battery weighing a few pounds added to THAT weight will be insignificant to the overall weight of the rear end.
.

 

[Mattax]

In the real world a shift of 50 lbs from the front to the rear can be significant.
It's significant in weight transfer for all sorts of applications (circle track, road race, drag racing) even though it only amounts to 1% change in front to rear weight proportion.

 

[crackedback]

@Mattax

Nice clean schematic update. Saved it, thanks

Big improvement from my stick man art skills.

 

[mopowers]

Reminds me of the car we had that ran faster with 2 batteries in the trunk than one. That battery weight sure slowed it down.

You mean it was faster even with all the weight from those extra battery cables??

 

[MadScientistMat]

I took the Ford solenoid approach myself, and didn't even run it through the switch. You kill the starter relay and there's no way the starter wire could be energized when the kill switch is on.

I also used an alternator with a separate voltage regulator so I could use an alternator kill.

 

[DionR]

It's currently an all stock wiring 67' Valiant. I'm working on a battery relocation to the trunk and I'm looking to run this idea by someone else to make sure I'm not missing something. I need it to be able to pass NHRA tech (disconnect shuts down the engine), but I also would like the starter (B+) circuit to only be hot when starting, and I'd like the hot wire from the alternator to be killed if the disconnect is flipped so that the only hot wires are in the trunk when disconnect is flipped.

Diagram is a bit crude and simplistic, but this is what I'm thinking.



View attachment 1716093928

I'm no electrician, so I could be wrong, but isn't the continuous duty relay in this diagram going to drain the battery when the disconnect is on? Looks like the disconnect is what powers the relay to close, which means it is a draw, right?

 

[DionR]

I would add that it seems like one issue is when the ignition circuit is powered by the alternator output because they are both on one side of a disconnect. As I understand it, the alternator will self power and also keep the motor running in that case, right? So the ignition and field circuit should be isolated from the alternator when the disconnect is thrown. Maybe that is covered above and I missed it.

I moved my battery to the trunk but didn't care about NHRA rules or having a a manual disconnect that would kill the car so I'm not much help in the actual application. I did add a disconnect but I just wanted to be able to isolate any live wires to the trunk when I throw my disconnect.

 

[33IMP]

I'm pretty opinionated about all this. First, why is it so important to have the starter dead? When was the last time one of those cables shorted? (And if it does you have a disconnect!!) You STILL need a HEAVY cable for the alternator and to feed power to the car. Just reconsider

But if you don't, I believe that "one wire" alternators are as much trouble as they avoid. If you use a "3 wire" or such, you can kill the field wiring and kill the output, and it is no longer a problem

another issue with "one" wire units is that because the v sensing is also on the one wire, they must have a MUCH larger charge wire than the same amp "3 wire" units.

Use a good quality FOUR terminal disconnect. Use the auxiliary terminals to kill something (even with a relay) that will kill the ignition/ compulter (if EFI) etc. You MUST wire this up in such a way that the alternator does not keep the engine running

Agree. I have a one wire alternator, and a two post disconnect I was unwilling to change. I had to use a moroso alternator disconnect solenoid to kill to motor when the disconnect is thrown. The moroso relay costs more that a good four post disconnect.