Community Forums

abolton99 · 11-21-2017, 12:42 AM

Hi - Curious if anyone has any knowledge and/or experiencing separating banks of 6v batteries that I have wired in Series-Parrallel. I've got 6 Lifelines that weigh a ton apparently and are causing my 2016 Mirada to list to one side. Currently they are installed in the storage compartment just toward the rear of the coach by the stairs. We have what I called Half Passthrough storage where there are about 10inchs of pass through height so I can't easily just slide them toward the middle.

My idea is to take two of the banks (4 batteries) and move them to the driver side to try and balance overall weight out. This would leave me with having to bring a negative and positive back across back across the coach to complete the parallel connections. This would essentially become my negative side and I would run my chassis ground from here and also back to my shunt for the BMK already installed on the other side. My OCP is already on the other side as well connections to my inverter and house DC systems. I'm guessing these is no more than 10 or so feet round trip.

I'm already using 4/0 for all my connections. I'm curious if there is a high risk that I wouldn't charge or utilize the bank on the driver side equally compared to the bank that is closer to the inverter and positive connections.

rarebear.nm · 11-21-2017, 01:21 AM

Never seen this done, but have thought about doing it, and then stopped.

IMO- I'd want to keep the length of both POS & NEG battery leads equal to at least the inverter. The 4-0 cable gives you best chance of making this work. Part of the unknown is the wattage of your inverter, assume it's also the converter. A good diagram of the battery cabling could be helpful in understanding if you're going to have a battery charge in-balance. Many battery banks are wired badly.

In my rig I have voltmeters attached to each 6v battery that at least gives me some idea how each one is performing. These voltmeters are fused and switched thus are not a parasitic load, also have two full system voltmeters, one in the basement another in the coach in the Trimetric unit.

I'd like to hear what others got to say on this issue. I'm sure its been done.

SCVJeff · 11-21-2017, 02:32 AM

Size of the wire really doesn't matter with respect to balancing the batteries, but like mentioned, length does. The way to maintain a proper balance to the charger is to take the ground from one location, and the positive from the other. Draw all this out taking into account everything: jumpers between the banks, and the return lines. The point of this is that the losses everywhere are equal so one bank doesn't finish before the other. Easy to do, just needs some planning

Sweetbriar · 11-21-2017, 06:06 AM

Considering 4/0 cable is approaching the size of the battery terminals I don't think you'll have a problem unless you plan to run the A/C off the inverter. You could get a minor imbalance between the banks with a large spike in demand but I suspect the banks will quickly equalize. Position the banks as close together as possible and keep the cable runs as short as possible and the potential will be minimized.

Lv2Roam2 · 11-21-2017, 06:31 AM

Given your description of clearance height your batteries may weigh ~ 66 lbs each. If accurate - you might not achieve your goal. Is it possible that something else is causing the lean? Is the lean common to the make/model?

vsheetz · 11-21-2017, 08:29 AM

My previous coach had two 6v batteries under the step, plus two that were added into a storage compartment on the opposite side of the coach. Heavy gauge wire of equal length interconnecting. Worked fine.

MSHappyCampers · 11-21-2017, 09:45 AM

Hi !

Welcome to IRV2! We're sure glad you joined the gang!

Definitely not my area of expertise! Keep her between the ditches!

Good luck, happy trails, and God bless!

abolton99 · 11-22-2017, 12:26 AM

Thanks everyone for the input so far. I've attached a mock up of what I want to achieve. I over course have OCP in place on my positive line with a disconnect as well as a shunt for the negative wire and the BMK. Just didn't include then in the drawing.

Lv2Roam2 - thats pretty close that are 90lbs a piece so I'm loading up that side with an additional 540lbs which honestly didn't seem like much. The fridge and sink are on the same side as well as my bunkhouse so could but it already has the want to lean. Never really noticed it before.

vsheetz, how long did you run that setup and did you have any monitoring? Did you wiring match up to what I've captured?

Danlb · 11-22-2017, 02:03 PM

I recently added a second bank of 6V Interstate GC2 batteries to my '10 Daybreak. The house batteries under the step (also GC2s) were connected with 2/0 cables with the ground directly to the frame. The second bank is in an aft compartment just under 20 feet from the front batteries. I grounded the rear batteries to the frame also and had a 20' long 2/0 positive cable made to run forward to the breaker that the main batteries connect to. I've also added a 2000 watt inverter to the rear batteries that I plug in my shore power cable into (through adapters). There is plenty of power to run everything but the converter and A/Cs. I can run the coffee maker, hair dryer and microwave in the morning plus the satellite and TVs as much as we want. The two banks of batteries have stayed very close to equal in voltage in the several trips we've made since adding this setup.

Changeup · 11-22-2017, 02:59 PM

How are your weights at each corner now? I'm thinking you might get a better result moving all the house batteries to the other side, while simplifying wiring changes.

powercat_ras · 11-22-2017, 03:21 PM

Don't forget that your batteries need to be in areas of the RV ventilated to outside air so that you can't get an explosive concentration of hydrogen gas if batteries generate hydrogen gas due to overcharging or equalization charging.

twinboat · 11-22-2017, 04:38 PM

Quote:

Originally Posted by powercat_ras

Don't forget that your batteries need to be in areas of the RV ventilated to outside air so that you can't get an explosive concentration of hydrogen gas if batteries generate hydrogen gas due to overcharging or equalization charging.

Only if you are grossly overcharging AGM Lifeline batteries. They are valve regulated to a specific pressure and do not off gas like open flooded batteries.

ByeTheWay · 11-22-2017, 04:53 PM

I have been told that separating batteries as suggested will cause problems.

twinboat · 11-22-2017, 06:05 PM

We're not going into outer space here, we're watching TV and lighting up our RVs. Maybe microwaving some frozen dinners.

A little imbalance in the cabling of a battery bank may shorten your battery banks life by a week.

Batteries discharge and charge like a barrel of water.
Tie 2 barrels together at the bottom. Drain one and the other will follow, whether they are 2 feet or 200 feet apart, as long as they are at the same elevation. The bigger the hose, the faster they balance out or equalize.

It makes more sense to use shorter cables where you can, then to make them equal, by adding unnecessary length.