Divorced battery bank wiring?

Interesting..... I was thinking 6v far seriesed with the near pair was the way to go too.

This is why I like 6v in parallel near and 6v parallel far.
Balance these parallel is easy. Then all must flow through the interconnect wire to create 12v. No imbalance.

If you must wire in series in each place then the close battery should not be grounded except through the other far battery.

Either way all power must flow the entire distance to be balanced.

Hi Mex,

Can you translate this for my pea sized brain? I do know what each word means but I can't extract the "meat" of what you are attempting to tell us.

MEXICOWANDERER wrote:
If all the time in the world is given to recharging the limit with too small of wire is the total CCA potential available.

Wire the "Local" in series so they provide 12 volt

Do the same thing with the "remote"

Now you have two 12 volt batteries (Consider each pair as though it were a 12 volt battery) now you can wire the two 12 volt battery banks in parallel.

Chris Bryant wrote:
One thing to keep in mind- in my opinion, balancing the batteries is really only advantageous in hi current charge/discharge applications (like a large inverter/charger). In typical low load/~50 amp charge RV setups I doubt it makes enough difference to matter.

I'll give an exaggerated but realistic example:

Start a generator with say a 50 amp charger. The closest batteries get 35 amps, the furthest 15, because of limiting resistance of the connecting wire. The monitor is connected to the closest batteries. The batteries are not going to like this. Neither will the owner's wallet.

If all the time in the world is given to recharging the limit with too small of wire is the total CCA potential available.

RJsfishin wrote:
Series the 2 distant batts, and bring it back as 12 volts

If you parallel them and bring it back as 6 volts, you will need larger cable because of the lower voltage, or suffer more voltage loss.

And I would use the frame for neg ground, I'd never run 2 cables

X2, I think this what BFL was saying too in his own way. :)

RJsfishin wrote:
Series the 2 distant batts, and bring it back as 12 volts

If you parallel them and bring it back as 6 volts, you will need larger cable because of the lower voltage, or suffer more voltage loss.

And I would use the frame for neg ground, I'd never run 2 cables

Thank you! That's the reasoning I was looking for!

I guess I did forget I have the frame to use as a electrical path. My old truck camper did not.

Series the 2 distant batts, and bring it back as 12 volts

If you parallel them and bring it back as 6 volts, you will need larger cable because of the lower voltage, or suffer more voltage loss.

And I would use the frame for neg ground, I'd never run 2 cables

I am looking at doing something similar here on my OFF-ROAD POPUP camper. My current 85AH standard issue Interstate batteries are ending their life expectancy and I want to get more Battery capacity for my activities. I am wanting to increase my battery capacity because of having high current two radios being used in my truck on occasions along with camping off the power grid.

My interest was to install two each 150AH 12VDC Trojan T1275 on the trailer tongue area and another two each same batteries in the bed of my truck.

I was considering these two layouts...


The two batteries installed in this drawing would be 150AHs each verses the 110AHs as shown..


As you can see my PD9260C 60AMP Converter/charger is located about 5-feet away from the main Blue Sea battery switch for the two 300AH batteries installed on the trailer tongue. The two batteries installed in the back of my truck bed will be around 8-feet away from its 2-conductor trailer connector mounted on the rear of the truck next to my 7-way trailer connection. The 2-conductor trailer cable with plug will be around an additional 8-feet long where it terminate into BLUE SEA battery switch. I am planning on using 4AWG size cables.

This of course will have a longer cable pair feeding the two 12VDC batteries installed in the truck when I am in my camping mode. I will monitor the charging currents when being charged to determine if I am getting my approximate 20 AMPS per battery when being charged.

I have previously been charging three batteries in my setup and the average DC current being drawn was 52-53 AMPS for my then three 12VDC batteries in parallel. I realize when I have have four batteries being charged the total current being drawn will be 15AMPs per battery minus loses in the battery cable lengths.

This is a diagram of my current battery arrangement on my POPUP. I will extend the BANK 2 leads and assocaited batteries to the back of my truck for the new installation.


I always have the capability of charging each group separately using my BLUE SEA battery switch arrangement which will be my PLAN B if it doesn't work out like I want it to.

I was thinking maybe it would be a work around if I used 2AWG battery cable in the longer cable runs to the truck bed but was unable to find a good 2AWG gauge 2-pin connector from etrailer. This would equal the mis-load better perhaps...

Being able to read my DC voltages and DC Currents when doing all of this will tell the story...

Just passing along to show what I will be doing to test out my next battery upgrade...

Roy Ken

There are pros and cons of parallel vs series when considering how batteries interact with each other under charge and when resting. I don't know if having the series link extra long or the parallel links extra long makes those factors better or worse.

Obviously the one long series wire is one wire, whereas the parallel would need two paths, but the neg path of those could be the frame, so it is still just the one wire needed.