130amp alt wire gauge to trunk

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340Duster247

340Duster247

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hey guys I finally got around to getting a new 130 amp alt. 3 wire from tuff stuff. I'm going to bypass the amp meter and I'm curious what gauge wire I should run. My battery is relocated to trunk with a cutoff switch.
 
so your battery is in the trunk and you want to run a wire from the alt to the battery?

just run a 8 ga wire to your starter
 
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If you are gonna do it that way I'd run 8 or 6. A one wire setup needs to have MUCH larger wire than a 3 wire. This is because of voltage drop.

But even with a 3 wire it's going to depend on "how your car" is wired. Think in your mind..........alternator..........some feet of ?? gauge to battery, battery cable "back up front."

Situation A:

You pull your "running" accessories off a major junction up front tied to the starter cable. You tie your switch, VR sensing to that post. That means this post will be at VR voltage, AKA 14V nominal.

BUT THE BATTERY (until it equalizes) will see the total voltage drop from the terminal "up front" back to the battery, and back up front to the alternator. This might mean, if there's much drop in the starter cable, that the battery will run "high" when charging. This might not be "much."

Situation B:

You pull your "running" accessories up front from a post tied to the alternator. This means the VR will keep that terminal at 14V nominal. BUT THE BATTERY is sitting way back there at the long run of that no8 or 6 or whatever it is, and now it will tend to charge "low" until it finally gets equalized.

Further, WHY are you running a separate wire? A 4 post disconnect solves all these problems.
 
The problem I'm having.
The new alt is still a 3 wire. I've already installed it and have yet to bypass the amp meter. I started it just to check my gauges and see what's going on. I have one volt meter from my racepak that gets power from a fuze block and reads 14.5-8 volts. My problem is I have another volt meter gauge on my fitech that gets power direct from battery. Only shows 11.8-12.2 volts. So I did some testing with an external volt meter. Coming into my factory amp meter I'm getting 14.8 volts. Coming out of my amp meter getting 14.8 volts. Out of the amp meter is a 10 gauge wire (for now) to the battery cutoff switch in the trunk. There I check voltage and only showing the 11.8 volts. So by the time it leaves the amp metre and ends up in the trunk it's losing the voltage

My thoughts are that the 10 gauge wire is too little and that's why the voltage is being lost?

I WILL be bypassing the amp meter.

The cut off switch has been installed for more than three years now and works correctly. I recently added fuel injection and never noticed the loss of voltage at battery till now
 
I didn't wire the battery relocation or the disconnect switch that was done by my father and I'll have to doublecheck exactly how he did it
 
You already have a large cable running to the back, that's all you need just tap into that wire, disconnect it from the battery and run it to the switch then get another cable and go from the switch to the battery. Run your alt to the starter and another wire from the alt to the interior amp meter, out of the ammeter to fuse block.
does this make sense.
 
There is a two gauge ground off the battery to the frame that I forgot to show.
 
If I wanted to eliminate the amp meter does this look right.
If so what amp fuse should be used.

IMG_2200.JPG
 
The maxi fuse? the alt is capable of putting out 130 amp, so if something happens like you leave a light on or your sitting some where listening to the tunes with your 600 amp stereo and then it cranks slow because your battery is low but it starts, your alt will go to max output for a short time then it will start dropping the amps output. No maxi fuse will take that plus once it's blown you are dead in the water. So you need a circuit breaker but only with the amp rating for the wire size. A 100 amp breaker will never break the circuit if the wire cant handle the current it will just melt the wire. From the factory they don't have the alt to the battery fused. I know painless and the others want you to use a fuse, personally I don't use them.
 
brian6pac said:
The maxi fuse? the alt is capable of putting out 130 amp, so if something happens like you leave a light on or your sitting some where listening to the tunes with your 600 amp stereo and then it cranks slow because your battery is low but it starts, your alt will go to max output for a short time then it will start dropping the amps output. No maxi fuse will take that plus once it's blown you are dead in the water. So you need a circuit breaker but only with the amp rating for the wire size. A 100 amp breaker will never break the circuit if the wire cant handle the current it will just melt the wire. From the factory they don't have the alt to the battery fused. I know painless and the others want you to use a fuse, personally I don't use them.
Click to expand...
Thnks
 
If I run 8guage wire from the alternator to the starter and install a circuit breaker how do I know what amp circuit breaker to use ?
 
you need to look up how much current a 8 ga wire will carry at 12v dc per length of the wire. just google it
 
The problem is, there are different strategies on wiring rear batteries, and the disconnect if used. "Where does" your main power feed come off? You don't really see it..........that I understand......in your diagram

Also be aware that depending on what you have for wiring changes, there are some voltage drop problems built into these cars, you are already addressing part of them with the ammeter bypass.

So far as the VR, the major issues are (referencing original wiring......) The bulkhead connector, ammeter, rare, but sometimes the welded splice connection in the dash black ammeter wiring, the ammeter, the ignition switch connector, and the switch itself.

The VR wherever it is MUST be within a tenth of a volt or so "at ground" with the battery

The VR power (sensing / ignition) wire must ALSO be within a tenth or two or three of "same as battery.

In the original wiring of these girls, THAT is almost always a problem. There was 1.5 or a little more drop in my original wiring, meaning the battery charged at........... 14V (the regulator) PLUS the 1.5V drop,.......... so the battery charged at 15.5!!!
 
67Dart273 said:
The problem is, there are different strategies on wiring rear batteries, and the disconnect if used. "Where does" your main power feed come off? You don't really see it..........that I understand......in your diagram

Also be aware that depending on what you have for wiring changes, there are some voltage drop problems built into these cars, you are already addressing part of them with the ammeter bypass.

So far as the VR, the major issues are (referencing original wiring......) The bulkhead connector, ammeter, rare, but sometimes the welded splice connection in the dash black ammeter wiring, the ammeter, the ignition switch connector, and the switch itself.

The VR wherever it is MUST be within a tenth of a volt or so "at ground" with the battery

The VR power (sensing / ignition) wire must ALSO be within a tenth or two or three of "same as battery.

In the original wiring of these girls, THAT is almost always a problem. There was 1.5 or a little more drop in my original wiring, meaning the battery charged at........... 14V (the regulator) PLUS the 1.5V drop,.......... so the battery charged at 15.5!!!
Click to expand...
+++++++++++++++
I have a 130 amp one wire on my fish. I ran an 8 gauge wire to the hot battery post on the starter relay, which is on the firewall next to where the heater motor would be. My trunk mounted battery cable ties in to it there, then a cable down to the starter, working great.
 
I'm now going to run 4 gauge from alt. To starter.
From starter to trunk is 2guage.
Is it neccacery to have a circuit breaker with wire that thick?
 
340Duster247 said:
I'm now going to run 4 gauge from alt. To starter.
From starter to trunk is 2guage.
Is it neccacery to have a circuit breaker with wire that thick?
Click to expand...


I would consider one. Especially now, with the internet, there are lots of this sort of stuff available such as race, marine, etc.
 
Sorry I forgot to mention, I have 2 wires coming off the pos. on my alt.

1 wire is 10 gauge going inside the car. (Bypassing bulk head connector) to a 40 amp Circuit breaker. Then to fuse box ect. (No ampmeter).

The other wire is 4 gauge from alt to starter. Then from starter 2 guage wire to batt cutoff -too batt in trunk. This is the wire I was curious about.
 
After looking through some wiring diags the fuse link is between the battery and amp meter
 
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