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cfetts avatar image

712 BMS wrong readings. Wired wrong?

I wired this 712 BMS like this?

However, I'm getting strange readings. Battery SOC never moves. Negative #'s. What did I do wrong? Here is 2 screen shots from running gen and not.

wiring diagram
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3 Answers
klim8skeptic avatar image
klim8skeptic answered ·

Try and put the shunt between the battery negative and the negative busbar. Shunt is labelled Batt side (battery) and Load/Charger side (- bus).

I assume the frame (chassis?) would go to the - bus.


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Which of the 8 batteries would I connect the shunt to? Am I not connecting directly to the negative battery via the busbar?

Hello cfetts, in the above drawing your load is must be connected to the PLUS (red) and minus(black) at the left hand side of the BMV702. There must be no other connections to the negative bus-bar.... only the shunt is connected to the negative bus-bar.

hope this helps.

Rob

I have it wired like the fig 8 above. See the first image I posted. Power to the shunt is simple. Something is wrong. Or I have a bad 712 bms

It might be good to post a photo of your batts/bus/shunt.

jwfrary avatar image
jwfrary answered ·

Hi

I'm pretty sure you have the shunt in the wrong place. It needs to go between the neg bus bar and the battery neg (you may have an additional bus bar for this. No other negs should attach direct to the batteries.

The shunt also has a particular way around it needs to go its marked on it.

The readings you are getting is because you have a circuit so your getting a charging voltage, and the voltage goes down when discharge but no or very little current is flowing across the shunt!

Send a pic of your install and we can help some more

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Justin Cook - Bay Marine Supply USA avatar image
Justin Cook - Bay Marine Supply USA answered ·

@cfetts, did you set the total Ah capacity in the BMV correctly? If you have 8 of these @210Ah each at 12v and you wired them in S/P to get 24v, you now have 840Ah at 24v. I concur with others that we'd like to see an actual photo or two of your wiring around the battery bank/busbars/shunt, but I definitely want to confirm your Ah settings as well.

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