Holy Voltage Drop Batman

[smfonic1]

OK so I'm the dumbarse around here!

I have been checking my voltage at the front battery, just to get an idea of how my alternator was keeping up. Well tonight I decided it was time to check the voltage at the amp. Last time I had done this was when I was running one 2400.

Voltage at the front battery was holding at 13 for the first 5-10 seconds than slow dropping into the 12s. Voltage at the amp instantly drop to 11 and than quickly into the 10s.

So, now it's time to buy a spool of 0ga. Hope three total runs will keep the voltage up.

[cxa0897]

yikes. how are the grounds from the amps? that could be a huge factor

[smfonic1]

Originally Posted by cxa0897

yikes. how are the grounds from the amps? that could be a huge factor

Frame ground, front and back.

Also think I'll ditch the distro/fuse block, picture in the middle below.
All the batts are fused so no need really for the extra fuses, just adding resistance at this point.

[spxtreme]

are you running 0 from front battery to back Pos and neg and 0 off alt? what amprage is your current alt?

[smfonic1]

Originally Posted by spxtreme

are you running 0 from front battery to back Pos and neg and 0 off alt? what amprage is your current alt?

Yeah it's all 0ga. Only 4ga I have are short runs from the distro into the amps and from the rear batts to the buss bars. I'll probably ditch the 4ga into the amps too and run 0 from the buss bars into the amps.

The alt is 250 amps.

[spxtreme]

either you have a cable issue or that alt is not doing that amperage its suppose to can ya show me what the alt looks like case wise

[smfonic1]

Originally Posted by spxtreme

either you have a cable issue or that alt is not doing that amperage its suppose to can ya show me what the alt looks like case wise

Wouldn't a 2 volt drop from front to back indicate a resistance issue?

Here is what the alt looks like:

[Burkem_10]

ditch those frame grounds and get some dedicated coppah. steel sucks for conductivity

[smfonic1]

Originally Posted by Burkem_10

ditch those frame grounds and get some dedicated coppah. steel sucks for conductivity

hmmmmm, this is real frame. If it were a uni-body I may agree.

[blackdragonx1186]

Originally Posted by smfonic1

hmmmmm, this is real frame. If it were a uni-body I may agree.

Indeed. A normal steel frame is around the same as 1/0 wire, in resistance. So I've read.

[spxtreme]

i would suggest welding cable i found it to be the best buy all i ever run front to back with large no voltage drop

[smfonic1]

To be more specific, I have a 0ga from the alt to the frame, a 4ga from the alt to the front batt and a 4ga from the front batt to the body. in the back I have 0ga from the frame to the buss bar and a 4ga from the body to the buss bar.

Do you think I could be losing some voltage from the front batt because it only has 4ga from it to the alt and body?

[spxtreme]

running that high of amperage stick with 0 do this ground from alt to neg on battery
0 from alt pos to battery
from front battery run pos and neg to back batterys it will eliminate any issue you might have with frame grounds
less head ache

[smfonic1]

You guys think two runs of 0ga Power and one 0ga ground front to back plus frame grounds? I always thouhgt frame grounds were solid....

[SINTORMAN]

Originally Posted by smfonic1

You guys think two runs of 0ga Power and one 0ga ground front to back plus frame grounds? I always thouhgt frame grounds were solid....

do two positives fused and 1 ground and upgrade your frame grounds too.

[666WMD]

Just to confirm, you have 1 (one) run of 1/0 from front battery to back battery? And you know you can only draw 300-350amp thru one run? And your amps are trying to pull 4-500?

[Lac.wit.bass]

Originally Posted by spxtreme

running that high of amperage stick with 0 do this ground from alt to neg on battery
0 from alt pos to battery
from front battery run pos and neg to back batterys it will eliminate any issue you might have with frame grounds
less head ache

SCRAP all the 4 gauge Wire and like spxtreme said run all 0 gauge.


Edit: oh and if you can double up on the runs it would sure help you out.

[Burkem_10]

I like the idea of 2 1/0 pos runs and 1 1/0 ned run along with the frame ground. and of course get rid of that 4 awg

[onefast68]

what batteries in the rear?

[profundus-sanus]

what brand is the wire you have now?

your voltage drop doesn't sound that crazy for 1 run of cca 1/0 on a 250a alt with a chassis ground.

witha 250a alt i would have at least 4 runs of ofc or 6 runs of cca

[SINTORMAN]

Originally Posted by profundus-sanus

what brand is the wire you have now?

your voltage drop doesn't sound that crazy for 1 run of cca 1/0 on a 250a alt with a chassis ground.

witha 250a alt i would have at least 4 runs of ofc or 6 runs of cca

you mean 2 + 2 - right lol? not 4+ and 4-

[onefast68]

i didnt realize cca wire was that much weaker...looks like i need to do some wiring upgrades as well.


is there and amp chart that compares both styles of wire?

[666WMD]

Originally Posted by onefast68

i didnt realize cca wire was that much weaker...looks like i need to do some wiring upgrades as well.


is there and amp chart that compares both styles of wire?

I can't remember where I saw it, but I read one that had a list of 1/0 through to 8awg and basically all the CCA was 20-30% weaker than the OFC.

Ie: 1/0 was 300amp for the OFC, 220 for CCA (20%). The smaller the wire, the worse it seem to get.

[KickinBlazer]

a buddy of mine had the same 2v drop from front to back battery as this guy..... useing a run of CCA so i said switch to OFC and he did, and now it differs bye 0.8v

[onefast68]

this is a great thread...i have 2 runs of 4ga cca to my rear batteries and was fixin to order up some wire this week and do 2 runs of 1/0 that cca...now thinking maybe 2 runs of ofc instead..fixing to get a 250amp alt that does 200amps at idle...