question

guy-cashmore avatar image
guy-cashmore asked

ESS system with two Multiplus II, one wired CT or two?

I have an existing simple ESS system currently using a single Multiplus II GX, mains connected on the input only, using the simple wired CT plugged directly into the Multi. It's working fine.

I want to expand the system using a second parallel slave Multi II (non GX) with VE.Bus.

Question is, does the slave require its own CT plugged in?

When I tried it without a second CT, VRM Remote Console reported export to grid at the same rate as the AC load even though grid setpoint was set at zero..

I will need to order a second CT if needed, hence the question.

Thanks, Guy

Multiplus-II
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5 Answers
Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @Guy Cashmore with a parallel system you cannot use the external current sensor!

the readings would be double, and ESS won't work properly.

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guy-cashmore avatar image guy-cashmore commented ·

@Daniël Boekel (Victron Energy Staff) OK thanks, that will explain what I've seen, what are the alternatives please?

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spudgun avatar image spudgun commented ·

Hi Daniël,

ls this a hardware or a software limitation? Is the current sensor not just providing a value to the inverter and then the inverter software responds? Would a power meter just be doing the same thing, providing a value to the inverter and the software responds? I don't fully understand why the readings would be double if you could explain with a little more detail please? Thank you.

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Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·
@Guy Cashmore

either run all power through the inverters (this also gives you backup function), or use an energy meter (or a combination of the above)

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guy-cashmore avatar image
guy-cashmore answered ·

@Daniël Boekel (Victron Energy Staff) Thanks, yes I'll run all the power through the units, easy in this case luckily, it wasn't installed like this originally due to the 32A limit but 2 x 32A with the second unit is ample. Better go and order some wire :)

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palom170 avatar image
palom170 answered ·

You need to insert a 3,5mm jack in the slave unit, it is only for inhibit the sensor in the slave unit. Please only the jack without clamp.

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wheeto avatar image
wheeto answered ·

Is there some official documentation around this limitation? And is there any chance of it being fixed?


I don't want to move to an external meter because the slow response time / control cycle time absolutely ruins the system's ability to keep to a grid setpoint.

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