Battery problem!!

[scottyhops]

hey everyone, i just moved my battery to the truck of my 420a eclipse 2g. it was running fine for the first 3 days. after that the voltage dropped. i have a 150a breaker right next to the battery, and I'm using 4gauge wire for the power and ground. the ground is fine and the power cable is fine but there is a voltage drop at the front of the car. any one know what it could be??

 

[dsm'r sk1mp]

When you say voltage drop, are you meaning you lose engine bay power and interior power is good or what?

 

[scottyhops]

the interior lights are a little dim, but i used a voltmeter and on the battery with it is at 10.8, when i did it in the bay it pulls up like 9.40. would that be because of the wire being to thin?

 

[reyg]

+1 what is happening exactly that makes you think that? Do you have a volts gauge or something you are measuring with?

 

[scottyhops]

yes. my turbo timer and voltmeter in my car are reading the same volts. and I've watched them drop. I've checked the ground connections there fine. the power connection drops between my battery to my bay. and the battery is not charging. do you think my alternator went and the power wire is to thin?

 

[Incoltnito]

Do you know what voltage is coming off your alternator? How about taking a voltage reading off the battery when the car is running. If the car is running, most all accessories are turned off, your battery should have a reading around 13.8 or so.

 

[reyg]

If you alternator "went" your car would completely die in a matter of minutes. Then you would need a new alt and maybe a new battery. The longer the wire the more resistance you have which in turn causes a voltage drop. However I'm talking big scale not sure how much it applies to small systems.

 

[NHerron]

If your battery reads 10.8 idling and 9.8 in the bay you have a very high voltage drop and I'm surprised you can even start that thing. Did you follow any guides for what gauge wires to use? Ohms law still applies and all wires/cables have a voltage drop per foot measured in OHMS per foot. If you didn't upgrade your alternator wire which senses battery voltage it will cause the alternator to see less voltage possibly causing an overcharge situation. BUT the undersized battery cables may be getting rid of the excessive voltage by losing it to resistance. Ideally, you should have the same voltage readings everywhere and if not you have resistance.

This is why I haven't done the relocation yet, too much of a hassle. Just for a cleaner look? Yeah right.

 

[bryanwheat]

4 gauge is too small to run from the front of the car to the rear. You need a 2 at least. Also did you run the ground to the rear of the car or did you run it to to the engine bay?

 

[scottyhops]

i needed to move the battery for my intercooler pipe. but i ran one wire for power and grounded to the rear. i read that some people was saying the 0 gauge was way over board. do you think if i swapped to 0 gauge that it would be to big?

 

[dsm'r sk1mp]

If its dim interior, and your getting a clicking sound when you try to start it(assumingg) I'm going to say because of the gauge of the wire, I think you fried your alternator, jump your car and see what your alternator is putting out. Do not just jump the car and pull the positive wire like some people say. The proper way is using your volt meter

 

[NHerron]

No. Bigger is better for the most part here.

 

[dsm'r sk1mp]

If you alternator "went" your car would completely die in a matter of minutes. Then you would need a new alt and maybe a new battery. The longer the wire the more resistance you have which in turn causes a voltage drop. However I'm talking big scale not sure how much it applies to small systems.

Actually a full battery will run a car for about two or three days depending on the amount of driving you do.

 

[scottyhops]

i think i might just buy a small battery kit so i don't have to deal with this hassle anymore and my ic piping will still work with the small battery

 

[bryanwheat]

Actually a full battery will run a car for about two or three days depending on the amount of driving you do.

IF you use any lights or accessories than it will kill it fast. You can go from new full battery to not enough power to run the interior lights in under an hour of driving.

i think i might just buy a small battery kit so i don't have to deal with this hassle anymore and my ic piping will still work with the small battery

Just go to the parts store and buy 10 feet of 2 gauge wire. You won't have any problems with the bigger gauge wiring.

 

[wrencher]

I have done many battery relocations to the trunk/rear of different types of cars.
Some that draw over 250 amps cranking.
I always use 00 gauge cable.
DC over the length of cable, too small you will have a voltage drop. Specially under a load (starting etc).
Voltage drop caculator;

Voltage Drop Calculator

 

[reyg]

I know its not the main topic but what I/C are you using that requires you to move the battery?

 

[zcoh2gdsm]

4 gauge wire is too small for that. 0/2 gauge at least.

 

[scottyhops]

on my 420a its turbo with garrett 60 trim, I'm using 2.5in piping and it comes off my tb and goes out and then down and would be where my battery was. that why my only options were moving my battery or getting a small battery, my car turns over fine

car off
at battery-12.36
in front by engine-12.35

car on
at battery-12.20
in front by engine-12.02

while cars running and i rev it the volts go from 12.02 on my voltmeter and drop to as low as 11.93.. i can't get to my alternator with out it being jacked up so thats all the info i have for right now....possible alternator is shot?

 

[reyg]

If you take it to AutoZone or advanced auto not sure which one they can test to see what your alt is putting out and it show signs that it is bad or going bad.