how are the batteries connected?

 

I have 0g going grommet the alt to the front battery and 3 grounds under the hood going to the front battery... I have 0g from the front to the rear battery and I drilled a hole and used a bolt for the rear ground...

 

I'm running a Optima Yellow Top D51R with stock alternator for a 750W paired Kicker amplifier and subwoofer. I had dimming issues but quickly resolved by installing a 3 Farad Capacitor inline before amplifier. I'm guessing you're running a higher wattage setup?

Most professionals will tell you to pair the same type of battery with the same specs so that it doesn't drain one faster than the other. It seems like you have wired them in parallel since your voltage reading is the same, the only thing that doubles is the capacity of amperage. If you were to connect in series, you will keep the same amperage, but double capacity in voltage. Having parallel connected two batteries will require almost double the time to charge up. Having an alternator that has a higher rating charging amperage will help your charge time.

Hope this makes sense...

 

Car audio is not my issue as I've been doing it for a living for a few years now... issue is when in drive sometimes it won't charge the battery's.. but in part neutral or reverse it works just fine... last night on my way to get my kid I didn't have one issue...

 

Voltage regulator stops the flow of amperage while you are in drive due to the fact it figures the first battery is fully charged. You may need a "battery isolator" that will switch off charging to the other larger battery.

http://carliving.info/isolator/index.html

https://en.m.wikipedia.org/wiki/Battery_isolator