I got my new denso 130 amp alternator today. I'm going to put it on my 68 cuda and run new wiring (skipping the amp guage) and also a ground wire all the way back to the battery in the trunk. Is there a formula for how big the wires should be for x amount of feet and x amount of amps ? Or just what's everybody else using ? Any advice would be appreciated.
wire size for high amp alternator
- Thread starter cudaboy
- Start date
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green67cuda
Well-Known Member
ground to the trunk???
there is a chart....i'd have to dig it up, but it indicates recommended charge wire size for alternator amperage.
if you have a pretty stock electrical setup, i'd go with 8-gauge minimum....i have an aftemarket ignition setup, and use 8.....if you have a high-power stereo, i'd use 1-2 gauges higher.
if you don't have a lot of current-drawing modifications, your alternator's 130-amp capacity will never be reached anyway.
you can only charge the battery so much.
the BEST thing to do would be to figure up your car's maximum current requirement (driving at night in the rain with the stereo cranked)
and use that for your car's used current.....gauge the charge wire from there.
there is a chart....i'd have to dig it up, but it indicates recommended charge wire size for alternator amperage.
if you have a pretty stock electrical setup, i'd go with 8-gauge minimum....i have an aftemarket ignition setup, and use 8.....if you have a high-power stereo, i'd use 1-2 gauges higher.
if you don't have a lot of current-drawing modifications, your alternator's 130-amp capacity will never be reached anyway.
you can only charge the battery so much.
the BEST thing to do would be to figure up your car's maximum current requirement (driving at night in the rain with the stereo cranked)
and use that for your car's used current.....gauge the charge wire from there.
GotDart
Well-Known Member
green67cuda
Well-Known Member
that's the chart, in a different format....but i don't agree with it.
yes, using too small of a wire will result in a drop, but that has nothing to do with their chart.
the fine-stranded wire is great if you have sharp bends.....it's more flexible, but, like in my case, there were no bsharp turns, so fewer, larger strands work better, as there are fewer I2R losses.....
some co-workers and I have been debating this, and feel that there really is no significant gain in using fine OR coarse wire of the same gauge if there are no sharp bends.
if i remember correctly, mine is THHN 19-conductor 8 AWG wire.....and with the battery disconnected (after starting), at full electrical load, i still have 13.5-14 volts at the front of the car, after the alt runs to the cutoff switch and BACk to the front via the 2 GA battery cable.
yes, using too small of a wire will result in a drop, but that has nothing to do with their chart.
the fine-stranded wire is great if you have sharp bends.....it's more flexible, but, like in my case, there were no bsharp turns, so fewer, larger strands work better, as there are fewer I2R losses.....
some co-workers and I have been debating this, and feel that there really is no significant gain in using fine OR coarse wire of the same gauge if there are no sharp bends.
if i remember correctly, mine is THHN 19-conductor 8 AWG wire.....and with the battery disconnected (after starting), at full electrical load, i still have 13.5-14 volts at the front of the car, after the alt runs to the cutoff switch and BACk to the front via the 2 GA battery cable.
dgc333
Well-Known Member
green67cuda said:
You are asking for trouble if you do not size the wiring for the capacity of the alternator. You are correct in that under normal conditions it's highly unlikely you will ever reach the capacity of the alternator.
It's the abnormal conditions you need to consider, for example, you run the battery down by leaving the lights on or give a jump to someone with a dead battery. Under those conditions the alternator will for a period of time will operate a max output. If the wire is under size you will over heat the insulation and it will fail causing a short potential or worest case start a fire.
dgc333
Well-Known Member
green67cuda said:
THHN insulated wire is not the best choice for automotive use it is not oil resistant. MTW would be a better choice since it's oil resitant and has a higher moisture resitance rating than THHN.
I put in an 80A alterator, and upgraded the wiring to 4 gauge. I picked up 25 feet of 4 gauge fine stranded wire on eBay for cheap, along with 2 gold plated ends. It was very easy to work with since it was so flexible.
Thanks for replying guys. I forgot to mention all of the info on my car. I'm running two electric fans, two fuel pumps ( one full time, another only for N2O) This car has NEVER had a good charging system. The deal with running a ground to the trunk was mentioned ...somewhere.haha...stating that the body is a poor ground when running the amps we run and the distance to the trunk mounted battery.
I was thinking about rewiring the whole car. Have any of yall had any experiences with the EZwiring universal kits? They're about $125.
I was thinking about rewiring the whole car. Have any of yall had any experiences with the EZwiring universal kits? They're about $125.
GotDart
Well-Known Member
A heavy gauge copper wire will always be a better conductor than a bunch of 30 year old sheets of steel spotwelded together.cudaboy said:
GoodysGotaCuda
Mr. Goody
I run a 90amp alternator with 6gauge. I'd go 4gauge for about 120amp. And 2gauge for anything more. You can pickup a snazzy circuit breaker like i did, i think they make them that high but im not sure.
This is my 80amp breaker, nice, clean, safe install. Ran about $35. It's made by 'blue sea systems'...it's for marine use, so check like West Marine and such, or on-line
http://goodysgotacuda.com/GGACPics/100_0817.jpg
This is my 80amp breaker, nice, clean, safe install. Ran about $35. It's made by 'blue sea systems'...it's for marine use, so check like West Marine and such, or on-line
http://goodysgotacuda.com/GGACPics/100_0817.jpg
superdart
Shade Tree Tinker Gnome.....
I'm using a 4awg charging wire to my buss bar, and 1/0 from the buss bar to the battery (in trunk).
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