Odd voltage.. why...?

[Ali1 10+ year member]

i have a redtop under the hood, directly connected to a yellowtop in the back. While the car is on, the yellowtop is reading 12.4v , while the red top (under the hood) is reading 13.9v.... anyone know why this is happening.

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[Calikid 5,000+ posts]

im not sure but its probably because the batt under the hood get better charge from the alt because is directly connected to it. it charges the 1st batt and then tries the 2nd one, if ur worried i will say to get a bigger alt. But i dont see a problem.

 

[killahbean 10+ year member]

you're getting resistence from somewhere.....check your connections......

 

[PESteele 10+ year member]

your using 2 different kinds of batteries might be a problem but im not sure. Also could be that your losing current in the wire. Are you using 1/0 awg

 

[killahbean 10+ year member]

your using 2 different kinds of batteries might be a problem but im not sure. Also could be that your losing current in the wire. Are you using 1/0 awg

doesnt matter about different batts.....Im running a stock and a yellowtop and gets same voltage on both batts......

 

[2loud4u 10+ year member]

im not sure but its probably because the batt under the hood get better charge from the alt because is directly connected to it. it charges the 1st batt and then tries the 2nd one, if ur worried i will say to get a bigger alt. But i dont see a problem.

not always you can have both them charging at the same time.

Stock bat under the hood and yellow top in the trunk and they read the same with car off or car on. just on how you wire it.

I would check the fuse on the wire between batterys or the ground on the rear batery

 

[Ali1 10+ year member]

your using 2 different kinds of batteries might be a problem but im not sure. Also could be that your losing current in the wire. Are you using 1/0 awg

Yes, I have 1/0 throughout the vehicle.... any more possible solutions?

 

[killahbean 10+ year member]

not always you can have both them charging at the same time.
Stock bat under the hood and yellow top in the trunk and they read the same with car off or car on. just on how you wire it.

I would check the fuse on the wire between batterys or the ground on the rear batery

with car on and off.....same voltage (I check almost everyday lol)

 

[Ali1 10+ year member]

not always you can have both them charging at the same time.
Stock bat under the hood and yellow top in the trunk and they read the same with car off or car on. just on how you wire it.

I would check the fuse on the wire between batterys or the ground on the rear batery

It's a 250amp fuse. I have one between the alt and the redtop. I also have another 250anl fuse running between the redtop to the yellowtop..... is that the problem? It was orignally between my redtop to the amp, but i got a yellowtop so i hooked that same wire to the yellowtop and used a short length wire from the yellowtop to the amp......

 

[2loud4u 10+ year member]

That is what i am saying it dont matter if you dont have the same type batteries.

Check your fuse or your ground.

Edit

Your fuse size is fine.

You have a problem somewhere eather a ground or blown fuse.

 

[Johnny Drama 5,000+ posts]

i have a redtop under the hood, directly connected to a yellowtop in the back. While the car is on, the yellowtop is reading 12.4v , while the red top (under the hood) is reading 13.9v.... anyone know why this is happening.

What is the yellowtop reading with the car off?

 

[Ali1 10+ year member]

they are tight connectiones, paint scratched to bare metal.....

 

[Ali1 10+ year member]

What is the yellowtop reading with the car off?

brb, i will check...

 

[Ali1 10+ year member]

i checked the voltage while car is off. Yellowtop shows 12.6, while redtop shows 12.5

 

[Flipx99 5,000+ posts]

it is odd that voltage is higher when car off than car on