Setup Wiring

DIY
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1

Hi - Newbie here. We recently had a Multiplus II installed at our dealership. While on a 5 week trip we discovered that our setup has been wired incorrectly because the voltage from the roof solar panel and the solar port were not showing on the Shunt and the Shunt readings did not match the Multiplus II readings.

We are going to call the dealer to request that they wire it correctly. I.E. The correct wiring should be that the negative wires from the MPPT 75/15, MPPT 100/30 and Multiplus II be wired to the negative bus and the negative bus be wired to the 500 amp Shunt. The negative wire from the Shunt should then be wired to the battery. Am I right?

Given that the setup has already been wired incorrectly could someone please look at the wiring diagram (attached picture) and let me know if there is anything else that is wired wrong so that I can let the dealer know? Thanks in advance for your help. Cindy

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2

This is correct. But that’s not what your wiring diagram shows.

Lets simplify the concept of the shunt so you know how this should work. The shunt essentially measures amperage. Therefore all amperage going in(charge) or out(loads) needs to go through the shunt or the battery state of charge will be inaccurate. Even a small amount of missed amperage will create inaccuracies that will multiply over time.

Here is what it should look like.

  1. ONLY the negative side of the battery should be connected to the battery side of the shunt.
  2. ALL negative loads should be connected to the system/load side of the shunt. This can be done via a bus bar. In other words the bus bar connected to the shunt and loads connected to the bus.
  3. NOTHING else should be connected to the battery negative.

In the diagram the Multiplus negative is going directly to the battery. WRONG. It should go to the system side of the shunt.

Negative bus wired directly to the battery. WRONG. It should go to the system side of the shunt.

The shunt is grounded to the chassis/frame. This is theortically OK for other negatives connected to the chassis but unreliable and not best practice. It is assuming good continuity through the frame and also relying and a failure point at the chassis connection. There should be a chassis ground here but ALSO, not ONLY. And it needs to be done correctly.

Let me know if that all makes sense.

3

Thanks for the reply. Yes, that makes sense. Basically what you are saying is what this diagram is showing, correct?

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I do not understand how a dealer could have gotten it wrong. It affected our vacation because we never truly knew what level the battery was at. Other than using a multi-meter.

Besides the shunt being grounded to the chassis/frame and the negatives being wired incorrectly, do you see any other problems? Thanks again for your help.

4

I wish I could say I am surprised the dealer got it wrong. Unfortunately I make a lot of money fixing dealer installed mistakes. That diagram is correct. I didn’t see any other problems with your wiring diagram.

5

Sad but true. Again, thanks for your help. I feel able to tackle these problems now.

6

You should show them that last diagram. Maybe print it and frame it for them. Also click the “solution” icon if you feel your question has been answered. I appreciate it.

7

I already have it printed to take with. I also printed your response. Thank you for telling me to click “solution”. I would not have realized that I should do that. Cindy