Rear batteries don't seem to be charging

[Airman21 10+ year member]

I have a 300amp alt and Duracell agm in the front with 2/0 going to the rear batteries (2 XS Power 3100). Noticed the volts on my Taramp 8000d was reading 11.7. Normally it reads low 14 until I am really pushing it then it drops down to low 13's. I started checking the amp before I would drive to work or home (1 hour each way). 11.7 at idle and when using the subs it would drop to 10.9. Next trip it started at 11.6. Seemed to drop .1 after each 1 hour drive with low volume. Front battery is totally charged so I know the alt is doing it's job and my electrical system is staying at 14.1 while cruising and 12.4 when idle so everything is good there. I checked my fuses everything is good. Is the 1 run of 2/0 not good enough? I would think it would be enough. Even with the subs turned off and a 1 hour drive the batteries didn't go up in voltage at all which makes me think maybe something with the wiring is the issue. Any ideas? I have the charger hooked up to the back batteries right now. Been pumping 40amps for 3 hours and still not fully charged yet.

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[dragon.breath 10+ year member]

Just start checking connections, like the rear battery ground to the car.

 

[Airman21 10+ year member]

Just start checking connections, like the rear battery ground to the car.

Yep I went out and checked connections. The positive on from the front battery to the rear was disconnected. Dang mechanics... lol.... everything is working as normal thanks...

Shocked that I was able to go 2 weeks on battery only for both amps. Those xs power are no joke.

 

[nyoc 10+ year member]

What Duracell are you running up front? I have 3 DURDC12-100P and I was wondering about using 1 up front for my starter. Thanka

 

[BOOMINGRANDPA 5,000+ posts]

check in line fuses.. 12.4 isn't very good at idle mine is 14.6 with no extra batts big 3 or big ga wire.. just let advance load test it..