FWC factory twin battery parallel hookup question

[pollux]

The following photo was taken from FWC's operation manual.

The two batteries are hooked up in parallel. It shows the charging cables all connected to one battery.

my Eagle camper's batteries are connected this way by FWC.

Is this setup correct?

I think all the negative wires should connect to the other battery.

 

[pollux]

This video show the battery connected in parallel. External cables are connected on either side of the battery group.

https://youtu.be/kd0qwLE5aNI

and this photo shows positive and negative wires connected to separate batteries

 

[rando]

Technically you are correct, the positive leads should be connected to one battery and the negatives to the other. Practically speaking in an application like this (relatively low current, short leads) it probably doesn't matter. If you wires are long enough, there would no harm in moving either the positive or negative leads to the other battery.

 

[PaulT]

One difference to keep in mind between the two photos is orientation of batteries.

First photo shows left battery positive at bottom and right battery positive at top.
Second photo shows both batteries positive at bottom.

Another thing to keep in mind is inconsistency of cable colors.

Top seems to be consistent in use of red for positive and black for negative.
Second uses black for both positive and negative with one red wire on positive.

They both appear to be 12v batteries wired in parallel.
Go to Harbor Freight, Home Depot or other store, buy a DMM and determine voltage polarity to put your mind at ease. One lesson to be learned here is that FWC used common color coding and the video did not. The DMM tells you for sure if a wire is positive or negative. Learn to use and trust your instruments

Paul

 

[pollux]

Ignore the wire color issue, this diagram by others should be more clear.
It is apparent that FWC's wiring is different.

 

[ntsqd]

That diagram, as Rando pointed out, is the preferred wiring design for a battery bank of any size. A survey of large battery banks will find them wired this way. In a pop-top I would do it the same way because I'm me, but I agree with Rando that it not being done that way probably isn't a big deal.

 

[Miketeleskier]

The hook up looks OK to me. However, I strongly suggest that a knife switch or an inline fuse be put between each battery and the camper wiring. That would allow the two batteries to be used together or one at a time. If one goes bad (when one goes bad), the bad one will establish the maximum capacity of the system so that neither will hold a charge.

 

[Jack]

The best solution is to go with two 6V batteries in series. AGM golf cart batteries are a good buy due to the volume.

If you have one battery in parallel go bad, it will quickly draw down the good battery. The most common failure mode is a failed cell in a battery, creating a lower voltage that causes the good battery to "charge" the bad battery. Finding this out in time to prevent significant damage to the good battery is not likely.

Since batteries loose capacity (amp hours) somewhat differently over time, the better battery in parallel will be drawn down a bit faster than the other. This is not major, maybe a few percent off the life of the batteries.

 

[Squatch]

The hook up looks OK to me. However, I strongly suggest that a knife switch or an inline fuse be put between each battery and the camper wiring. That would allow the two batteries to be used together or one at a time. If one goes bad (when one goes bad), the bad one will establish the maximum capacity of the system so that neither will hold a charge.

Another option is a marine battery switch. These wire the cables into it parallel. You can choose to charge either or both batteries or disconnect both from the camper. This allows you to keep one battery charged in reserve in certain circumstances that might need that.

https://www.westmarine.com/buy/blue-sea-systems--e-series-compact-battery-switch-off-1-both-2-no-alt-field-disc--3831393?cm_mmc=PSGoogleGSC%2520-%2520Product%2520Type3831393&product_id=3831393&adpos=1o1&creative=108421552324&device=c&matchtype=&network=g&gclid=EAIaIQobChMIpfrmr7zA1QIVC4RpCh2PuQjUEAQYASABEgLjfvD_BwE

 

[fwctaco]

From a circuit theory perspective, connecting positive out to one battery and negative out to the other battery only matters when connecting batteries in series. There is a negligible amount of resistance added by the wires and connections to the second battery, but it will not affect operation, and when wired either way, the resulting circuits are equivalent.

AFAIK, the newer FWC models already include a master battery shut off switch. I would not bother adding a switch or fuse for each battery as it is relatively easy to disconnect one of the batteries from this setup by simply removing the wires, and you are probably replacing both batteries at that time unless one battery turns out to be defective early on.

 

[bike4mee]

I have 2 batteries. I want to use 1 for my trolling motor, the other stays in the camper to run things. After use I want to charge it with solar during the day. How to wire this? They say if you put another drawn down battery in parallel it could hurt your fully charged battery. Should I get another solar modulator box and charge it away from the first one? Or does it matter?

Also does it matter that both batteries are different manufactures. Like putting duracell and energizer batteries in same flashlight?

 

[Wandering Sagebrush]

Don't put them in parallel. Look for a quick disconnect (Anderson?) to move controller output between batteries. Primary stays connected to camper. Or at least, that's my 2¢ worth.

 

[ntsqd]

Concur, make up some method to charge them separately. Be that heavy duty jumper cable clamps or pigtails with Anderson connectors or whatever.

 

[PaulT]

Think of this situation as similar to the truck battery/alternator system and the camper battery/solar system with a battery separator between them. Duplicate that solution between the two batteries in the camper using another ACR. That will allow recharging the trolling battery without affecting the camper battery.

You can think about it as a boat system with the camper battery as the boat starting battery and the trolling battery as the boat house battery.

Use large Anderson connectors to allow easy connect/disconnect of your trolling motor to the ACR & ground. You should be able to set it up so that you don't have to muscle the trolling battery back into the compartment if that helps.

Paul