question

neeyee avatar image

Multiplus Not Reading Voltage Sense Wires

I have a 5kva Multiplus connected to a 48v 300Ah lead acid battery bank. There is a roughly 0.8v drop between what battery voltage the inverter sees as displayed on VeConfigure and actual battery voltage. E.g Multi reads 49v whereas battery reads 49.8v when measured with a multimeter at battery and inverter terminals.


I have connected the Voltage sense cables to the appropriate terminals but these seem to have no effect on the Multiplus' voltage readings. I even restarted the Multiplus a few times and no improvement in its voltage readings (still off)


The voltage sense terminals that fit into the Multiplus have ferrules about half inch long crimped on them - I am beginning to think I need longer ferrules?


There is no GX device or BMV in this config as it is a simple backup system. I need a reliable means to read the correct voltage as the low battery cutoff and absorb and float setpoints absolutely need an accurate reading.

MultiPlus Quattro Inverter Chargervoltage
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6 Answers
klim8skeptic avatar image
klim8skeptic answered ·

I have connected the Voltage sense cables to the appropriate terminals but these seem to have no effect on the Multiplus' voltage readings

Plz tell us you have directly connected the voltage sense wires to the battery terminals.

Not some random place between the battery and multi....

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neeyee avatar image
neeyee answered ·

Yes there are two bus bars, one each for the DC positive and DC negative connection. The voltage sense cable goes from the DC positive busbar to the Vsense + terminal on the inverter and the other cable from the DC negative busbar to the Vsense - terminal of the inverter.

Battery and inverter are directly connected to the DC busbars as well with 70mm2 cable crimped with an hydraulic crimper.

I even used extra long ferrules on the voltage sense cables so they could make good contact inside the terminals.

I have tried this with a few Multis and Quattros and it appears they do not see or use the voltage from the voltage sense cables/terminals.

Perhaps the voltage sense functionality is now deprecated or broken in the firmware?

Or is there some setting or dip switch needed to make voltage sense work?

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walter-casey avatar image
walter-casey answered ·

I have also connected the voltage sense to no effect.

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ludo avatar image
ludo answered ·

I have exactly the same problem, would have been nice to see some reaction or hint from Victron here.

In "charge" mode with 120A the Multiplus switches to float to early

in "Inverter" mode with 200A the Multiplus sees "low battery voltage" too soon and shuts down

Also it would have nice if the unit would receive the voltage fom my battery-manager 712 over bluetooth, for this purpose i fitted a bluetooth-dongle to the multiplus ;)




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ludo avatar image
ludo answered ·

OK, so i now checked some things, changed battery from "individual" to LiOn, set charge current to 120A and send the settings to the MultiPlus.

BUT, this time (for the first time) i didn't send only the modified, but ALL settings.


Now my AC-current limit is working, AND my DC-sense- wiring is working.

Thanks for nothing, Victron.

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ludo avatar image
ludo answered ·

Ok guys, I have another update for you ;)

Working with VE-config i saw the sense lines are working just as they should.

So i cleaned everything up, disconnected the MK2 and reconnected my Bluetooth-dongle so i could read inverter status on my mobile.


Today i turned on the coffee-machine, the Inverter-display started flashing "undervoltage".

Checked BMV, battery full, checked inverter-votage, battery low.

Started my generator, multiplus immediately switched to absorption, sense-wiring clearly NOT working.

So, again, i connected the MK2 and my PC, immediately the charge-current stepped up from 70 to 100A, sense-circuit working again ????


After some coffee and overheating some cirquits in my brain, i found the origin of my (our?) problem: as soon as you connect the bluetooth-module, Multiplus will take the feed-voltage of the BT as sense-voltage and disregard connected sense lines.

Probably for temperature and voltage sensing, as i have LiOn installed i have no temperature sensors.


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