Parallel battery wiring help?

[streamer99]

I'd like to replace the batteries in my 2019 FC, but haven't done so before and am definitely a rookie at this. I know these are hooked up in parallel, but am a bit confused how exactly. My understanding of how to wire 2 12V batteries in parallel:
- Connect positive terminals of battery 1 and 2
- Connect negative terminals of battery 1 and 2
- Place all positive connections on positive terminal of battery 1
- Place negative connections on negative terminal of battery 2

I have 2 sets of wires coming in to my battery compartment from the trailer. I believe one (the larger gauge wire) is for the converter, and the other is the inverter. However, it is wired different than I would expect:
- Converter: positive connected to battery 1, and negative to battery 2
- Inverter: positive connected to battery 2, and negative to battery 1

Why are the positives for both converter/inverter not connected to same battery, and the negatives for both connected to the other battery? Is this just because there isn't space on the terminal for both?

Any guidance would really be appreciated. I'm attaching a labelled picture of my battery setup, if it is needed.

[richard5933]

Your thoughts on how to join the two batteries is correct - the two positives get connected, and the two negatives get connected.

With all the various things you have joining your two batteries, you might benefit from using a negative and a positive bus bar. The negative bus bar would connect to the negative terminal of one battery, and the positive bus bar would connect to the positive terminal of the other battery. This provides as balanced a draw as possible.

If you have a shunt for a voltage monitoring system, it goes between the negative bus bar and the negative terminal of the battery.

All the other positive and negative connections get made to the bus bars, not to the batteries. This serves a few purposes - not only does it make for a neater installation which can be understood easily, it moves the connection points away from the batteries to the bus bars where they are much less susceptible to corrosion. In my book, I try to never have more than one cable (other than the parallel cables) attached to a battery terminal.

[uncle_bob]

Hi

While connecting things as you describe is "best", simply hooking them up is ok. The advantage of best vs ok is pretty small in something like an AS trailer.

Bob

[streamer99]

Thanks for the replies! I think a bus bar is exactly what I need- it seems like this would organize this all much more cleanly, and it would be easier to see what is going on.

Last question on this: what does the shunt for voltage monitoring system look like? Is this just another positive and negative connection coming in to the battery compartment that I might have missed?

[thewarden]

It is not likely you have a shunt. If you do, it is surely hooked up wrong. There is only one negative cable connected to one side of the shunt and all other negatives are connected to the other side of the shunt.

What you have is a normal factory wiring connection for your AS. Wired in the way yours is now make sure the draw is balanced. It is also correct to put all the positives on one battery and the negatives on the other. In a small battery bank, 2 batteries, it really does not matter a great deal how the positives and negatives are connected up as long as the positive cables are connected to the positive post, negative cables to the negative post.

[uncle_bob]

Originally Posted by streamer99

Thanks for the replies! I think a bus bar is exactly what I need- it seems like this would organize this all much more cleanly, and it would be easier to see what is going on.

Last question on this: what does the shunt for voltage monitoring system look like? Is this just another positive and negative connection coming in to the battery compartment that I might have missed?

Hi

Depending on what shunt system has been installed, they each look a bit different. ( = there are multiple brands and multiple models ). All of them require the battery negatives be run *only* to them. If you have one and only one wire going away from the battery negatives, follow it and see what you find. If you have multiple wires, you don't have a shunt.

Another easy thing is to look for the display. There is only one unit on the market that runs without one. It's quite new so you are unlikely to have one unless you put it in yourself.

All sorts of details on what a BMV-712 looks like:

https://shop.pkys.com/victron-energy...y-monitor.html

click on the "additional information" tab.

Bob

[richard5933]

Originally Posted by streamer99

Thanks for the replies! I think a bus bar is exactly what I need- it seems like this would organize this all much more cleanly, and it would be easier to see what is going on.

Last question on this: what does the shunt for voltage monitoring system look like? Is this just another positive and negative connection coming in to the battery compartment that I might have missed?

Even if you don't have a shunt/BMS right now, setting up a negative bus bar for all your negative connections will greatly simplify adding one later on.