How To Install Dual Battery?

[spencerkrew69]

well its a new battery up front, i was gonna go with the deka intimidator for the back i forgot the size though.

[L-banga]

OK. SO WHAT YOU GUYS ARE SAYING IS THAT ALL YOU HAVE TO DO IS GET A HO ALT, TWO AUDIO BATTS, AND WIRE THEM IN PARRALLE WITH FUSES IN THE POWER CABLE BETWEEN THE TWO. IS THERE NOTHING MORE TO DAT? CAN I ADD A 2ND HO ALT AND RUN THE POS CABLE FROM DAT TO THE BATT IN THE TRUNK OR IS THAT NOT NESSECRY?

[Andrew]

I'm not aware of it making a difference in which is put up front and which is in the rear. Whichever you'd like to do up front is going to work. That's like saying it wouldnt work if you put a 1400 up front and a 2400 in the back?

[roscoe1129]

Typically you want to put the larger battery closer to the amps since that is what they will draw the reserve from first

[TechSys]

This is info that I've gathered, but may be off a little.

It's best to have the same type/size of batteries. This way one doesn't drain off the other and cause problems. You can run the ground wire of the second battery to the frame of the vehicle. You don't really need to have fuses, but it is recommended for safety reasons. If you do install fuses, one under the hood withing 18" of battery on the positive wire, one in back withing 18" of battery on positive wire.

Running the batteries in parallel will result in 12volt plus the amperage of the 2 batteries. Example: 2 12volt batteries at 800amps each will give a 12volt 1600amp system.

Running the batteries in serial will result in 24volt, but keep the amperage the same. Example: 2 12volt batteries at 800amps each would give 24volt 800amps.

It's also a good thing to do the Big 3 upgrade, whether you have a stock alternator or a H.O. alternator.

Now that's that's over, and I hope it's correct (it is from what I can tell and understand). I currently am running 2 batteries in my Astro with the stock alternator. Both batteries are 900amp each. I used 4/0 wire for positive and ground, with no fusing installed. The 4/0 is run under the van and zipped tied to the frame. To get into the van, I didn't use rubber grommets but instead used 2 house electrical box metal conduit ends (can't remember what they're called actually). Maybe a pic will explain it better.

When I first did this, I was VERY scared of blowing the batteries up. It's been 3 months, or longer, and haven't had one bit of problem.

[Eric B]

+-------fuse--------------------------fuse-------battery

and yes you can ground to the chassis and an isolator only helps if you run your system with the engine off, which if you need two more batteries thats probably not a good idea

Im curious, why would you need to fuse it twice on the same cable, because its DC and current is flowing one way wouldnt you just need one up in the front and thats it, or is there something im missing?

[roscoe1129]

Im curious, why would you need to fuse it twice on the same cable, because its DC and current is flowing one way wouldnt you just need one up in the front and thats it, or is there something im missing?

dc current is not directional just because the fuse blows in the front (due to it grounding, etc), you still have it hooked to a battery in the rear...correct? therefore it is still live and very capable of doing damage to your car.

Edited June 3, 2007 by roscoe1129

[Eric B]

dc current is not directional just because the fuse blows in the front (due to it grounding, etc), you still have it hooked to a battery in the rear...correct? therefore it is still live and very capable of doing damage to your car.

thanks for the quick response...i was just puzzled by that for a minute. But once the fuse blows doesnt it become an open circuit not allowing electricity to flow?

[roscoe1129]

thanks for the quick response...i was just puzzled by that for a minute. But once the fuse blows doesnt it become an open circuit not allowing electricity to flow?

yes as long as you have one on both ends of the cable

and they both blow but if you dont have one b4 the back battery its gonna keep the wire live

[sean 371]

I used 4/0 wire for positive and ground, with no fusing installed.

Hm...Is there a reason you arent running fuses? The only scenario I can think where you wouldn't want them is in a competition vehicle where you need maximum power transfer...And what are you running that you need 4/0 wire?