Upgrading Alternator, Can I Run A Second Wire From Alternator To Battery?

mrburitto

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Hello,

So I just installed a new 150amp alternator in my K20 because I am installing a stereo system and power inverter. I had planned on upgrading the wire from alternator to the starter but am finding I physically cannot get to it. I can't even really access the starter because my headers are in the way.

I was wondering, can I just add another wire (2AWG) going from the alternator directly to the battery and leave the existing factory stuff in place?

It seems a little janky, and it seems like it wouldnt be a good idea for some reason. But after looking at wiring schematics and thinking about it I can't think of any reason why NOT to do it. Everything else would still get power, and the current should prefer the path of least resistance which would be the large wire going straight to the battery, so the smaller wire shouldnt be getting too much current. I would like to just replace everything but like I said, I physically cannot get to the bus or to the starter without taking a bunch of stuff off and I dont want to do that.

Thanks, any help is appreciated!
 

Blue Ox

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Hello,

So I just installed a new 150amp alternator in my K20 because I am installing a stereo system and power inverter. I had planned on upgrading the wire from alternator to the starter but am finding I physically cannot get to it. I can't even really access the starter because my headers are in the way.

I was wondering, can I just add another wire (2AWG) going from the alternator directly to the battery and leave the existing factory stuff in place?

It seems a little janky, and it seems like it wouldnt be a good idea for some reason. But after looking at wiring schematics and thinking about it I can't think of any reason why NOT to do it. Everything else would still get power, and the current should prefer the path of least resistance which would be the large wire going straight to the battery, so the smaller wire shouldnt be getting too much current. I would like to just replace everything but like I said, I physically cannot get to the bus or to the starter without taking a bunch of stuff off and I dont want to do that.

Thanks, any help is appreciated!
My '85 has only one wire going to the alternator, and it goes straight to the battery. In fact, it's integral to the battery cable.

Shorter run, less connections,... what's not to like?
 

Blue Ox

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straight to the battery is the bestest way to wire a 'one wire' alternator.

:)

It's not a "one-wire" but the output terminal of the alternator is attached to the battery terminal and it's part of the factory battery cable.
 

mrburitto

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Ok so sounds like creating a loop and running another wire going direct to the battery wont be a problem? Thanks!
 

75gmck25

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I used some junkyard parts to replace my charge wire. I got one of the firewall junction blocks (same as the one next to the brake booster) and mounted it on the passenger side fender well. Then I pulled the larger gauge charge wires from a 90’s GM truck, including the fusible links.

The first wire runs from the battery positive over to the junction block. The 2nd wire runs from the junction block to the BAT terminal on the alternator. This charges the alternator, and also provides an easy to access power point. At that power point I connected power for my headlight relays (kit from LMC) and also installed a connector for my battery tender. I paid about $10 for the parts from the junkyard, and a few dollars for the extended battery terminal post from Autozone.

Bruce
 

AuroraGirl

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Hello,

So I just installed a new 150amp alternator in my K20 because I am installing a stereo system and power inverter. I had planned on upgrading the wire from alternator to the starter but am finding I physically cannot get to it. I can't even really access the starter because my headers are in the way.

I was wondering, can I just add another wire (2AWG) going from the alternator directly to the battery and leave the existing factory stuff in place?

It seems a little janky, and it seems like it wouldnt be a good idea for some reason. But after looking at wiring schematics and thinking about it I can't think of any reason why NOT to do it. Everything else would still get power, and the current should prefer the path of least resistance which would be the large wire going straight to the battery, so the smaller wire shouldnt be getting too much current. I would like to just replace everything but like I said, I physically cannot get to the bus or to the starter without taking a bunch of stuff off and I dont want to do that.

Thanks, any help is appreciated!
as you said, you are allowing the thing that puts the most load on the system, the battery(I would think?), to have a suitable wire. Any current draw that would have your alt put a lot out should be okay for that regard. However, I would want to run battery positive directly for accessories that are carrying this load. If your truck is basically stock, nothing extrodinary, but you want that extra amp for lets say needing less time turned on to charge battery, boosting, etc then i dont see any issues with your idea. but im also not an electrician or electrical engineer or anything but learn-as-i-go-diyer, so my logic may be flawed
 

mrburitto

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Thanks for the input everyone, gonna go ahead and run the second wire.
 

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Ricko1966

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I would not use 2 gauge and would only use a single wire battery to alternator no thicker than 6 gauge.
 

mrburitto

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I would not use 2 gauge and would only use a single wire battery to alternator no thicker than 6 gauge.

6 gauge is only rated to handle about 130 amps max... Why would you put in a wire that cant handle the full possible output of your alternator?

Also, it doesnt hurt to have extra capacity lol. Just means less heat and easier for the power to flow. Oreilly sells it by the foot. I just bought a couple feet and slapped it in. No big deal.
 

mrburitto

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2 gauge seems to be a bit of overkill. American Autowire uses 6 gauge wire and 175 amp mega-fuses in their Alternator and Main Power Connection kit.

https://www.americanautowire.com/media/productattachments/files/downloads/92972153 510476 IN 0.1.pdf

It is a little lol. But I figured if Im doing this, I want to make sure that the extra amperage prefers this connection over the small stock wire that I am leaving in there. I want it to have very little resistance even under full load. Doesnt hurt me any to have a thicker wire there.
 

Ricko1966

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The wire gauge acts as a current limiter so you don't cook the alternator. Been there, done that.
 

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