Battery bank wiring question..

[nalasha79]

We have a 2017 Jayco Precept 35S and we have a question on the way the battery bank is wired. There are two batteries in parallel, but there are positive cables running off both of the battery positive posts. We are going to install a wirelessmultimeter.com unit with a shunt to keep an eye on things, but we need to know if there is a reason the cables were installed this way. Using the shunt (300amp) I would plan to move all of the positive cables to the same post; after the shunt. Anyone know if all cables to one post would cause trouble or if this was done to make things better? There is plenty of stock cable length to move them all to the same post...

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[RoyBraddy]

If it were me i would do it this way... All 12VDC loads coming from the top POSTIVE TERMINAL shown in this photo. If you are going to have many DC Circuits the best thing to do is install a high current multiple TAP BUS BAR. I would never put more than two 5/6-inch ring terminals on one connection. The reason is that both battery cable wiring will be drawing the same DC Current from each battery. i.e. the Battery Terminals wiring is the same length for the same DC Load...


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This is not so much a big deal for small DC CURRENT loads but for the very high DC Amperage loads it really comes into play for both 12V Batteries seeing the same load...

Doing this helps the two batteries maintain the same performance over time when seeing the same discharge and charging DC Currents...

For installing a monitor shunt I would place it in the NEGATIVE Terminal cable and frame ground. With the batteries balanced in the above photo will then show the total DC Current being monitored... This also gives you bit of protection from shorting things with the low potential DC Current that will be feeding your monitor DC AMPS meter movement... I would put a small current fuse in this line feeding you meter. The DC Current here will be a very low reading current wise.

Blue Sea Bus Bar (AMAZON)

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The Battery Experts on here can explain it better than I can...

Roy Ken

[nalasha79]

If there is no reason for Jayco to have wired the cables the way they did, I totally agree and understand your reasoning. I changed the cable paths in my last camper to your diagram as they had all loads connect to just one of the batteries. That method didn't seem like it would've distributed the load over the two batteries. Anyone know if there is some reason for Jayco to run positive cables to both batteries? Only 1 negative cable is used...

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[RoyBraddy]

oops double post - second time in a week - guess I'm losing it haha...

[Danno]

The only reason I could think to have 2 positive cables is so they can run 2 separate circuits, say one for the main TT power and the other for the brakes. Regardless, it doesn't really matter how you wire it because we are dealing with very low current draws, so just wire it the way it's suits you best.

[nalasha79]

Thanks Danno. Although, wouldn't the nature of the separate circuits occur in the actual circuit outside of the power source. I think so... So the point of that goes away if I understand that correctly. The only thing I can come up with is too much draw to one post of a single battery, but I just don't know.... Anyone?

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[Mustang65]

The diagram that Roy has on his post is the most efficient method for charging and discharging the battery bank. "ALL" POSITIVE connections for the TT go to the positive terminal of battery #1 of the battery bank as "ALL" NEGATIVE connections go to the negative terminal of battery #2. There should be connector cables between the 2 batteries (negative to negative and positive to positive. The connector cables should be at minimum the same AWG as the other battery cables. Using the diagram that Roy added ensures that both batteries are electrically balanced (well the best that they can be) for charging and discharging.

If you would like more information regarding wiring up your TT batteries here is a link to the document that supports this wiring diagram. It is also located in my album under batteries. For more battery information you can scroll through our "RVing with SOLAR" social group. The link is also below.

Don

My Registry

RVing with SOLAR

[Vicr]

As a 35S owner I can answer the question. The battery posts are not tall enough to stack the inverter cables onto so they used a different posts.