Wiring two batteries in one car?

[Angelboy863 21]

I've watched over and over on YouTube how to wire two batteries in a car.

I'd have one as my main starter battery and one in my trunk.

Do I just have the positive from my main battery go to the positive on my second battery? (fused of course) and the negative just go to the ground and I'm all set?

And another question, having this battery setup, will it put more stress on my alternator?

Thanks I appreciate the help.

[pmureika 31]

You are correct positive to positive negative to negative.Its just like jumping a car.As far as harder onthe alt. it depends how low you run the car without it running and let the voltage get to low.If you use it normally, no it wont be harder on the alt.

[Tremonic 7]

Run a positive from the front batt to the back batt and you can frame ground the rear batt. Just be sure to grind off the contact area for the ground. As far as being hard on the alt it's all a matter of current draw. If you constantly draw the batts down and the alt has to recharge 2 instead of 1 well common sense will tell you that yes, it will be harder on the alt. But for your setup (as long as it's still the setup mentioned in the other thread) you should be fine. Again make sure you do the big 3. When you make the run from front to back fuse both ends of the wire no further than 18 inches away from each batt.

[swagger_wagon468 53]

So EVERY single pos+ run must be fused at both batts? Do the neg- runs need to be? So if I were to have two runs of pos+ 1/0 then I would have 2 fuse holders under my hood? And 2 in the back? (Assuming I have only one batt in the trunk?)and what if you add another batt? Would that pos+ need a fuse also? (Going from batt to batt in the trunk.) thanks

And sorry for all the questions.

Jonathan

[Tremonic 7]

So EVERY single pos+ run must be fused at both batts? Do the neg- runs need to be? So if I were to have two runs of pos+ 1/0 then I would have 2 fuse holders under my hood? And 2 in the back? (Assuming I have only one batt in the trunk?)and what if you add another batt? Would that pos+ need a fuse also? (Going from batt to batt in the trunk.) thanks

And sorry for all the questions.

Jonathan

The grounds do not need to be fused. Yes every run of positive needs to have a fuse on both ends. If your wire shorts somewhere in the middle and there isn't a fuse on both ends then it will not disconnect from both batts and will sit there and ark until it catches something on fire. Every run of positive from one batt to another needs fuses on both ends no more than 18" away from the batt unless you have a battery bank and your running from one batt to another while they're sitting right next to eachother.

Edited June 15, 2011 by Tremonic

[swagger_wagon468 53]

Thanks man.

[Tremonic 7]

Thanks man.

No problem man glad I could help

[edouble101 314]

I've watched over and over on YouTube how to wire two batteries in a car.

I'd have one as my main starter battery and one in my trunk.

Do I just have the positive from my main battery go to the positive on my second battery? (fused of course) and the negative just go to the ground and I'm all set?

And another question, having this battery setup, will it put more stress on my alternator?

Thanks I appreciate the help.

Here is a diagram that may help you

I run a positive and negative from battery to battery. Each battery is also grounded at the frame.

A battery does add an extra load to an alternator when the battery(s) needs a charge.

Depending on your system demands, from my experience dual runs of 1/0 +&- from battery to battery is worthwhile. Two batteries wired in parallel can discharge much more amperage than what a single run of 1/0 +&- or a 300a fuse can handle. Just a thought.

[pmureika 31]

I've watched over and over on YouTube how to wire two batteries in a car.

I'd have one as my main starter battery and one in my trunk.

Do I just have the positive from my main battery go to the positive on my second battery? (fused of course) and the negative just go to the ground and I'm all set?

And another question, having this battery setup, will it put more stress on my alternator?

Thanks I appreciate the help.

Here is a diagram that may help you

I run a positive and negative from battery to battery. Each battery is also grounded at the frame.

A battery does add an extra load to an alternator when the battery(s) needs a charge.

Depending on your system demands, from my experience dual runs of 1/0 +&- from battery to battery is worthwhile. Two batteries wired in parallel can discharge much more amperage than what a single run of 1/0 +&- or a 300a fuse can handle. Just a thought.

If you run it like you only had one bat the load would be the same.

[edouble101 314]

Incorrect!

One battery is a load. Additional batteries wired in parallel are additional loads, period. The amount of load is dependent on the battery(s) quality and condition.

[pmureika 31]

Incorrect!

One battery is a load. Additional batteries wired in parallel are additional loads, period. The amount of load is dependent on the battery(s) quality and condition.

I ws refuring to 2 brand new agm bats. They just make one big battery.

[Tremonic 7]

I understand what your saying but even so it will be more of a strain on the alt. Discharge a regular battery and then discharge one twice its size and the bigger batt takes more to charge. Hence more of a load on the alt.

[swagger_wagon468 53]

I plan on having 3-4to xs d3100s in the back. I have a d5100r up front. How many runs from front to back would u suggest? 2+ & 2-? Ill be running 2 saz3ks and a 100.4. 270xp alt.

[pmureika 31]

I understand what your saying but even so it will be more of a strain on the alt. Discharge a regular battery and then discharge one twice its size and the bigger batt takes more to charge. Hence more of a load on the alt.

They are hooked together as one battery it will only put a bigger load if one of the batteries is bad. Same thing will happen if your one oem bat goes bad , it puts a bigger load on the alt.

[swagger_wagon468 53]

All Knu OFC. Incase you were wondering.

[Tremonic 7]

I plan on having 3-4to xs d3100s in the back. I have a d5100r up front. How many runs from front to back would u suggest? 2+ & 2-? Ill be running 2 saz3ks and a 100.4. 270xp alt.

I would do a run from the front batt and a run directly from the alt for the + runs and yes 2 should be fine. As far as the - runs the best place is actually on the block as close to the alt as you can get. It wouldn't hurt to run a frame ground also in the rear as close to batts as you can get. I'm assuming you have the big 3 done? And all of this wiring is going to be 1/0? If you want to be a little more sure about it you could always do 2 runs of 2/0.

[pmureika 31]

Are you talking two new batteries or what?

[swagger_wagon468 53]

Yes all 1/0 Knu OFC. Big3 is done in 1/0 welding cable.

[Tremonic 7]

Yeah I would stick to what I mentioned. One from front batt, one from alt (both wires fused on both ends). Grounds - one frame ground in rear, 2 block grounds as close to the alt as you can get. Do this and you should be golden.

[Angelboy863 21]

First off, thanks everyone on your input it all really helps

And about the stress on the alternator, edouble

[Angelboy863 21]

First off, thanks everyone on your input it all really helps

And about the stress on the alternator, edouble, are you saying that running a pos and neg wire from starting battery to rear battery will sort of lessen the stress on the alternator?

I plan on doing big 3 with 1/0 gauge wires, I will fuse every pos, and my car will power a saz 1500 at 1 ohm, maybe 0.5. I will have the batteries mentioned earlier (shurikens) and might upgrade alternator if it's too low (idk my alternator amps but will check)

[Angelboy863 21]

Anyone know the stock alternator amps on a 03 maxima?

[pmureika 31]

110 amps

[///M5 2,833]

Incorrect!

One battery is a load. Additional batteries wired in parallel are additional loads, period. The amount of load is dependent on the battery(s) quality and condition.

Perhaps simplifying this would help.

If your alternator provides all the current necessary at all times for your system then the battery load "won't" matter.

Quotes for two reasons, one starting drain needs to be recharged and there is some "conditioning" charging required. Both I wouldn't consider an issue or is there any difference really between one or two in that case.

If of course the opposite is true and your alt can't keep up then indeed since you are discharging two batteries, the second will be an extra load for sure. Considering you feel you need a second this is most likely to be the case....otherwise of course I'd question why you are adding a second battery anyways.

[Tremonic 7]

With a 110 amp alt you should be ok with an extra batt like you mentioned. Definitely get a voltage meter and hook it up at the amps power supply so you can monitor voltage at the amp.