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matt.u 03-06-2016 07:50 PM

what is the point of more runs of 1/0
ok first of all i understand you want the resistance to be down to keep voltage up to the back. but then i know if you have a 200 amp alt your battery bank is in the back you will really only be getting the alternator amperage going through the wire. 1/0 i was reading somewhere is good for 100 amp. so 200 amp alt you have 4 runs of 1/0 what would be the point?

the only reason i ask is because i am looking at replacing the runs of wire i have with 4/0 only one run 250 amp alt. would it really help if i were to run 2 runs of 4/0 or not?

Beckerson1 03-07-2016 09:51 AM

Re: what is the point of more runs of 1/0
Depends on length of wire. A 20 foot run of 1/0 wire is good for 120A to 200A give or take which chart you look at.

You decrease that run the amperage goes up.

IMHO it would be a waste of resources if you did two runs of 4/0. The amount of gain you may see (depending on location of batteries) would be minimal as you can't increase the current capacity of the alt by running 4/0 vs 1/0.

Even 4/0 IMHO would be WAY overkill.

IMHO size the power run appropriately to the size of your alt. One run of 2/0 should be plenty for 250A.

Now if you're running wire in between batteries size the wire based upon your estimated MAX current draw (be it either max output of alt or max system current draw. So say your connecting a front battery to a rear bank. The alt to front battery should be sized according to the length of the run and current required. Usually less then 3 feet which means 1/0 should be more then plenty @ 250A max output. 2/0-4/0 here would be a waste.

Over on DIYMA we had a thoughtful discussion about the Big 3 and Why its so accepted as gospel and automatically suggested if one has dimming issues. The topic was about stock setups (stock alternator) and why one would replace the power run from the alt to battery. Even though from the factory (on newer vehicles) this wire run is sized correctly to the power output of the alt. Basically the premise is people seem to think this somehow increases the power output of the alt when in all honesty your not gaining much of anything from this wire run. The whole issue of dimming or even VD comes down to grounds.

matt.u 03-07-2016 06:40 PM

Re: what is the point of more runs of 1/0
ok that is what i wanted to see i kind of figured as much. i know a decent amount about electrical but i guess you could say not as confident as i should be.

profundus-sanus 03-08-2016 08:24 AM

Re: what is the point of more runs of 1/0
So if you have a 200a alternator 1 + & 1 - 1/0 run to the back that are 15 feet long you're looking at a .7v drop from just the wire alone. Assuming your drawing more than 200a. Jumping to 2+ & 2- would cut that voltage drop in half.

It all just depends on how much your willing to give up but many go by the rule of thumb of 1 run of +&- 1/0 ofc per 100a of alternator current to the back. That will keep you around a .3v drop from wire.

Voltage Drop Calculator i use this calculator for simplicity on determining wire runs.

matt.u 03-08-2016 12:41 PM

Re: what is the point of more runs of 1/0
Kool thanks a bunch man.

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