question

Paul B avatar image
Paul B asked

Multiplus II VE BUS graph and System battery amps graph on the VRM amps are differant ???

these two graphs on the VRM are showing the SAME voltage but the VE bus says current is zero where the correct current on system battery volatge is saying 1.9amps (I have checked this with a external INLINE amp meter and 1.9 amps is correct)

this differance is all the way across the graphs

this is on a MP II 48/5000 FW 459

anyone know why I suspect that this is causing the charger to keep pumping in 1.5 amps into my battery bank even when they are full at 56 volts then the voltage just keep going up.


I have a suspision that its the ESS assistant but I have not had time to test this , Ill do this over the weekend by removing the ess assistant and then seeing if the two become equall,

but if anyone has another test that I should carry out as well, please fire away with some suggestions.

Multiplus-II
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1 Answer
mvader (Victron Energy) avatar image
mvader (Victron Energy) answered ·

Hi Paul,

You wrote:

> anyone know why I suspect that this is causing the charger to keep pumping in 1.5 amps into my battery bank even when they are full at 56 volts then the voltage just keep going up.

Thats impossible. When the battery is full the charger stops on voltage. Not on current. A (slightly) wrong current measurement will do no harm.

And Indeed, inverter/charger current measurement is not accurate. It doesnt need to be either.


To explain the difference: I’m assuming that the current shown on the System graph originates from another measurement? A battery monitor, or canbus connected battery? Indeed, they are more accurate. The error of the value shown by the inverter charger will vary on temperature, voltage, etc. The device doesnt measure actual DC current. It measures other currents and parameters and then estimates the DC current. See also:

https://www.victronenergy.com/live/ccgx:ccgx_faq

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Paul B avatar image Paul B commented ·

Thanks for the reply


the MP II charger is also suppose to STOP on HV allarm as well

all the time in this graph were the voltage is rising. the HV allarm has been on (Once triggered the HV allarm the battewry BMS holds a HV allarm until the battery drops to 80% SOC then the HV is released (I control the release value)

The other device is a BMV 700 and if you look at the graphs in the VRM its showing the 1.5 amps being pumped in ALL night all the time and my separate inline amp meter also shows this to be true its what the BMV sees and a separate inline check sees.

Yes I agree it should not happen but to me and my readings it is.

I am trying to fined out why its happening . there are NO other items attached except Victron gear

and it still happens EVEN if a VE BMS gives a HV signal to the MP II it still is pumping in a consistant 1.5 amps, remove the ESS assistant and it seems to stop

MP II 48 5000

Venus GX connected to MP II via VE BUS

BMV700 connected to venus GX by VE Direct

VE BMS

This to me seems to be causing my sky high uncontrolled over voltage


Re using the VE BMS unit on a non standard 123smart battery BMS

The below is how I see the VE BMS working or am I incorrect

The Victron VE bms unit is a 3 signal wire control loop

Black temp disconnect

Blue High voltage disconnect

Brown Low voltage disconnect

The blue and brown from mem maybe the opposite way around , but you get the idea


All 3 loops are normally CLOSE and as such if any one of them is opened the VE-BMS produces a error out via the VE BUS to the inverter telling it to stop charging or if the low cable is opened then it sends a trigger via the BMS that say stop using the inverter power


So just because I use a relay to open or close these will make NO difference to the signal to the VE bus network

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mvader (Victron Energy) avatar image mvader (Victron Energy) ♦♦ Paul B commented ·

Are you saying you are using the VE.Bus BMS not with Victron batteries but with other batteries and a 123 smart bms? (Also not victron).



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