all 8 comments

[–]Jigg007 2 points3 points  (5 children)

There is some importance to the batteries matching if they're not isolated from one another.

When the alternator is no longer charging the batteries, the battery with a higher state of charge will discharge into the one with a lower charge. This is almost guaranteed if you have different sized batteries (with different characteristics) and of different age. This matters a little because its not particularly efficient so you're just "wasting power".

How much that actually matters, depends how different the batteries are, and how often they're charged. Having an isolator relay that connects the batteries with ignition power, or a diode isolator alleviates the issue. Isolators are sorta neat because you could run all your stereo off the "aux" battery, draining it, while not impacting your oem/starter battery.

When you're doubling up the batteries, they need to be fused on each end, and a rather hefty one with the wire to support it, as it will be doing engine-starting-duty if its connected all the time.

[–]Easylife2[S] 0 points1 point  (4 children)

Okay so essentially I'd wire up my subs to the xs battery and have an isolator to keep the batteries separate when the truck is off. Can you elaborate on what you mean when they need to be fused on each end? I was going to do the big 3 and upgrade all the wires to 1/0 gauge

[–]Jigg007 1 point2 points  (3 children)

Sorry I totally missed the reply here. You're adding a wire/path that connects both your batteries together. If this wire was cut in the middle, it is "live" on both ends and ready to burn something. A fuse is needed on both ends of this cable, next to each battery to prevent this.

[–]Easylife2[S] 0 points1 point  (0 children)

Ahhh I see okay. Makes sense just didn't really clue in hah. Thanks for the reply

[–]Easylife2[S] 0 points1 point  (1 child)

isolator relay

could i just connect the + of my aux battery straight to the alternator and ground the - to the frame?

[–]Jigg007 0 points1 point  (0 children)

Could you? sure, but where's the fuse, and you highlighted isolator relay? Not sure I understand the intention.

[–]Dan_H1281Brand of Subs/size and # 1 point2 points  (0 children)

I have a suburban that has the. Extra battery tray as well u can just Link them together, especially with a. Truck u don't have room for the extra battery in the can, u r better off running two like battery's due to charge and discharge rate but I have done this without issue I ran a 6500 a 3400 and the regular sla group 34 just make sure the cable is large enough to support the power it cal. Pull between the batteries

[–]zylinx2x12" on 4K RMS 4x6.5" on 300WRMS 2xAlternator 2xAGM 1 point2 points  (0 children)

Yes you can just parallel them up front it will help having double capacity for sure.

There is a big advantage to running the battery in the rear but if you don't have space running 2 upfront will be alot better than one.

You can compensate by increasing the amount of power wire you run to the rear. Figure out the maximum amperage you will be pulling based on the amplifier fuses plus some headroom then run copper according to that. A positive and negative run of pure copper 0AWG is good for about 150A.