question

bitcrusher avatar image
bitcrusher asked

How to wire up a (second) smart shunt to measure alternator power with cerbo?

Hi there,

in my RV I already have a BMV monitor connected to the cerbo to measure SoC of the battery bank.
Now, in the new Venus OS update, you show a possibility to measure the amps coming from alternator (with a second smart shunt). That's great!

How do I have to wire it? In my case i have a buck boost between starter batt and leisure batt. Do I simply connect the shunt between the output of the buckboost and the leisure bank? in the plus-cable? (Isn't the shunt running on reverse polarity, then?)

I could not find a wiring diagram for this new application, can u please make one?

Thank YOU!

cerbo gxSmartShunt
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2 Answers
Matthias Lange - DE avatar image
Matthias Lange - DE answered ·

The shunt always have to be in the negative wire.

How is your BuckBoost wired now? Is the negative connected to the chassis or to a negative busbar?

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bitcrusher avatar image
bitcrusher answered ·

Ok thank you.

It is connected to a negative Bus bar. The Bus bar is connected to chassis, and connected (via bmv shunt) to negative Pole of the leisure batt.

So then the new smart shunt and the „old“ one will be connected in series?

Or is it necessary to „bypass“ the SoC shunt on the negative side of the leisure batt?

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ commented ·
They have to be in series.

I'm not 100% sure but I think you have to connect the negative of the BuckBoost and the chassis together to one side of the new shunt (system side) and the other to the busbar.

No chassis connection directly to the busbar.

But this only works properly if you don't use the chassis as negative for some loads.

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bitcrusher avatar image bitcrusher Matthias Lange - DE ♦ commented ·
There are two negative star points in chassis, (that the car manufacturer has made ) on the first, alternator and Starterbatterie is connected (front of ducato) . In the second one in the back there is the negative of the rv distribution box connected. And also the PE of 230V distribution.

… well I think that is too cumbersome to change all these connections to get alternator power monitored….

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