Need battery expert

[RockyMtns]

I've just added two 6v batteries and created a sealed & vented compartment under my dinette. Now I'm trying to decide if I should leave my original 12v single battery on the tongue also or remove it. The advantage of leaving it would be to keep the additional amp hours. What would be the disadvantages (if any)?

[Herk7769]

Originally Posted by RockyMtns

I've just added two 6v batteries and created a sealed & vented compartment under my dinette. Now I'm trying to decide if I should leave my original 12v single battery on the tongue also or remove it. The advantage of leaving it would be to keep the additional amp hours. What would be the disadvantages (if any)?

I believe the disadvantages to what you are suggesting has been covered pretty well in several threads here. Off the top of my head, I can't think of a single advantage.

[RockyMtns]

As stated, the potential advantage as far as I can tell would be the additional amp hours of having a third battery. It would also alleviate having a no power situation if a cell failed in one of the 6v (seem to be a common concern in the discussion threads although I find it unlikely).

I have no doubt this has been covered at some point in one of the many hundreds of thousands of threads. However, four hours of reading and every possible combination of search reveals no information. Anyone want to humor me and point me in the right direction?

[Triguy]

Originally Posted by RockyMtns

I've just added two 6v batteries and created a sealed & vented compartment under my dinette. Now I'm trying to decide if I should leave my original 12v single battery on the tongue also or remove it. The advantage of leaving it would be to keep the additional amp hours. What would be the disadvantages (if any)?

If you opt for this, I would install a switch to change between the two banks of batteries. The first bank (older 12 volt) and the second bank (newer 6volts in series) are different enough in size and age that the 12volt would be overdischarged when in use and overcharged when charging and the converter or other charger could misread the power "needs" of the bigger 6volt bank and undercharge it (those are basically the disadvantages).

The disconnect would allow you to leave it on the tongue in case you needed it but isolated from the new battery bank. Blue Sea makes a disconnect that allows you to change between bank 1, 2, 1&2 or none.

[Himcules]

here's a pic of the stock battery wiring in my 2013 berkshire 390bh

[Herk7769]

[QUOTE=Himcules;358396]here's a pic of the stock battery wiring in my 2013 berkshire 390bh

It doesn't look like there is enough wire to swap the two positives.
You are going to have to deal with the "less than optimum" battery configuration.

Your battery bank connections are pretty heavy and exactly equal so the mismatch in resistance should be low.

[Himcules]

here's a full bay pic so you can see the slack. you should be able to swap them around... i still haven't traced the cables to see where they connect to. the factory could have it correct on mine.

[Herk7769]

Ah, your choice then. Swap the two negatives or the two positives (but not both!)

[boowho]

Originally Posted by herk7769

To balance the bank, the lower two connections should be swapped.

The inverter positive should go on the other batteries positive and the "Camper's" positive should go where the inverter's is now.

Thanks, Herk..... If the cables are long enough to allow, I'll switch them.

Boowho??

[boowho]

Originally Posted by Himcules

i'm picking my new 390bh up tomorrow. i'll take a pic of the battery bay and trace those down for you if Silver doesn't get a chance to before then...

i'm not an electrical engineer but to me, it seems either lead pair is not pulling a balanced load based on your diagram. each lead pair is pulling from half the bank first instead of from across the entire bank of batteries. based on what i have learned, to get a balanced pull you would want to have the positive and negative leads connected at the furthest ends of the bank from each other. so in your diagram, go diagonal corners for your connect points to get the draw balanced acrossed all 4 batteries instead of just two...

i'm sure an electrical engineer can clear this up better than me...

the diagrams posted before in this thread do show a balanced draw across the entire bank..

Thanks to both you and Silver for the info/help.


Boowho??