Alt charging low?

[hatedonmostly 5,000+ posts]

My front battery has always charged at 14.3-14.5 at idle with the front battery and big three done.

Today I installed two 12v 20ah batteries in the rear. I didn't have any 0 gauge, so I used the run of 4 gauge KLMX that I already had installed, which is rated for 100 amps of current.

I understand that the 4 gauge wire can't handle enough current to recharge those batteries quickly enough, so because of that, I am getting worse voltage drop that when I did not have any rear batteries. I plan to remove one battery, which should be fine on the one run of 4 gauge; then get 1/0 gauge in the future and put in both batteries.

But with all four batteries in, car running and no accessories on, I was resting at 13.85 on all batteries (front and two rear). I don't understand why my issues with the rear batteries would cause my front battery to charge lower as well.

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[audiolife 5,000+ posts]

bigger wire and run a neg run back to the front alt bracket.

 

[ahole-ic]

My front battery has always charged at 14.3-14.5 at idle with the front battery and big three done.
Today I installed two 12v 20ah batteries in the rear. I didn't have any 0 gauge, so I used the run of 4 gauge KLMX that I already had installed, which is rated for 100 amps of current.

I understand that the 4 gauge wire can't handle enough current to recharge those batteries quickly enough, so because of that, I am getting worse voltage drop that when I did not have any rear batteries. I plan to remove one battery, which should be fine on the one run of 4 gauge; then get 1/0 gauge in the future and put in both batteries.

But with all four batteries in, car running and no accessories on, I was resting at 13.85 on all batteries (front and two rear). I don't understand why my issues with the rear batteries would cause my front battery to charge lower as well.

The reason is because in a parallel circuit, the voltage stays constant throughout it. Since those batteries aren't charged, they are trying to draw LOTS of current. The morale to the story? More batteries don't help anything.