Dual 12v Battery Hookup Question

[remdog_1]

Purchased 2 new 27 series 12v batteries, added 2nd battery box and have them both vented to outside. Hooked Positive to Positive and Negative to Negative.
Question is do I hook Pos and Neg from camper to one battery, or hook one camper lead to positive on one battery, and negative on the other battery?

[dballentine]

Thank you, everybody!

Dave

[pianotuna]

Hi,

If you wish to understand the "why" surf here:

correctly interconnecting multiple twelve volt batteries

Yes, you can center tap for two batteries, or use a buss bar.

dballentine wrote:

Why?

Both positive terminals are at the same potential, as are both negative terminals. (Ignoring I2R loss in the interconnecting cables.)

I would think connecting the positive from the converter to either battery (or midway between the two, for that matter), and the negative (ground) to either battery, would work as well.

[time2roll]

dballentine wrote:

Old-Biscuit wrote:
Positive from one battery to converter/dc distribution
Negative from other battery to frame ground

Why?

Both positive terminals are at the same potential, as are both negative terminals. (Ignoring I2R loss in the interconnecting cables.)

I would think connecting the positive from the converter to either battery (or midway between the two, for that matter), and the negative (ground) to either battery, would work as well.

It will work. Just not as well over time. Resistance of the cables is small but so is the internal resistance of the battery so it does end up having an accumulated effect of working one battery harder than the other. The higher the load the greater the effect. The more batteries the more the effect will be.

If you pull power for a large inverter off one end of a stack of four batteries. The lead (close) battery will initially handle twice the load of the tail (farthest) battery.

[RoyB]

You want to balance the drain and charge currents feeding your two batteries. This means keeping the like cable lengths the same lengths.

This can be achieved by wiring in this fashion...


If you wire up your two 12VDC batteries in this fashion you see the first battery cable lengths are shorter then the cables feeding the second. The first battery will drain and charge at a different rate than the second battery will do. The small drop in resistance with the two different lengths really come into play when you start drawing heavy battery currents. Lots of charts on here from the local battery experts showing this happens.


This is the plan at any rate to balance both batteries as best you can with equal lengths of battery cables wired in the proper sequence..

Roy Ken

[RoyB]

oops double post

[dballentine]

Old-Biscuit wrote:
Positive from one battery to converter/dc distribution
Negative from other battery to frame ground

Why?

Both positive terminals are at the same potential, as are both negative terminals. (Ignoring I2R loss in the interconnecting cables.)

I would think connecting the positive from the converter to either battery (or midway between the two, for that matter), and the negative (ground) to either battery, would work as well.

[Old-Biscuit]

Positive from one battery to converter/dc distribution
Negative from other battery to frame ground