question

nzmikec avatar image
nzmikec asked

Multiplus not responding to Batrium BMS commands

Hi All,

Asking in the modifications section as I know batrium BMS isn't officially supported with Victron.

Im using a MultiPlus-II-GX with 14 leaf modules (14s2p) and Batrium WM5 BMS. The BMS is connected over CAN and shows up in the device list of Venus and shows SOC, Voltage etc so the communication is at least working. The issue I have is that if I tell the batrium to halt discharge (in control logic) the Multi just carries on discharging. When I issue this command in the BMS it changes the Discharge current limit (DCL) in "parameters" under the device to 0.0A so the message is getting to the venus device however there is no response in slowing / halting the discharge in the multi.

This behaviour is the same with or without DVCC enabled.

I am using ESS in "Mode 3" and my control loop makes no corrections based from the BMS however my understanding is that the Multi will respond to Mode 3 power requests only if it is within the capability of the multi and the battery. Maybe I am mistaken?

Any help would be greatly appreciated!

Regards,

Mike

ESSBMSDVCC
2 comments
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@nzmikec, is your battery set up to also send a charge voltage to the battery, or does it only send current limits?

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nzmikec avatar image nzmikec Izak (Victron Energy Staff) ♦♦ ·

Hi @Izak (Victron Energy Staff),

The charger is sending charge voltage and both charge and discharge current limits. See the attached image, both charge and discharge currents are zero as I have set manual charge off and discharge off states in the BMS. The unit continues to discharge however.

Fortunately the Multiplus responds to the charge current messages and stops / slows the charge.

My issues seem to only affect discharge messages.

Thanks for taking the time to read and respond to my post.

Regards, MikeC

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9 Answers
mvader (Victron Energy) avatar image
mvader (Victron Energy) answered ·

Hi @nzmikec,

When the grid is disconnected, ie the system is running in inverter aka island mode, then the maximum discharge current cannot be regulated. Discharge current depends solely on the loads; until either the BMS sends a CCL=0, or disconnects the battery (typically by relay or mosfets) or until the voltage has dropped to the DC low disconnect voltages configured in the inverter/charger by the installer.

When connected to the grid, then (as long as DVCC is indeed enabled) discharge current can be controlled. And it does work, at least with our tests with any of the battery makes and models on the compatible battery list.

I hope that helps!


UPDATED: added CCL=0 effect when in inverter mode

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nzmikec avatar image
nzmikec answered ·

Thanks @mvader (Victron Energy Staff)

My issues seem to only affect grid connected discharge limiting as above.

Thanks for taking the time to explain the above. Much appreciated.


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so you say it -does- shutdown when no grid is available?

when grid is available, the inverter should enter 'passthru' mode in ESS systems.

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nzmikec avatar image
nzmikec answered ·

Sorry @Daniël Boekel (Victron Energy Staff)

Ive not tested the behaviour when off grid, im actually not using the AC out so I can't confirm. My issue is that the Multi will not respond to DCL values when grid connected operating in ESS Mode 3.

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Hi @nzmikec

Because in ESS mode 3 the multi is controlled directly by the external EMS, the only value the system listens to in ESS mode 3 is DCL=0, the system will then stop discharging the battery. The same applies for CCL (CCL=0 means stop charging)

the CVL value is always listened to.

in ESS mode 2 the system does listen to other values than 0 as then the GX device is in control, and you only set the grid power setpoint, and enable/disable charging / discharging

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nzmikec avatar image nzmikec Daniël Boekel (Victron Energy Staff) ♦♦ ·

Thanks @Daniël Boekel (Victron Energy Staff)

This is what I had hypothesised in my original question. If true, this isn't entirely clear in the ESS manual as under the Mode 2 & 3 details under bullet point 3.2 this note states the inverter will operate within the inverter and the battery capacity.

  • Note that it will always remain within battery and maximum inverter power limits: when the battery is full or when the maximum charge current as configured in VEConfigure is already met, it will not draw more power, and when instructed to discharge with 10000 watt while it only has a 2500W inverter capacity, it will discharge with 2500W until the battery is empty.


https://www.victronenergy.com/live/ess:ess_mode_2_and_3

Its looking like ill need to go to mode 2 and test from there.

Thanks for your continued help,

Mike Christiansen


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Hi @Daniël Boekel (Victron Energy Staff),

I have the ESS system running in mode 2 now using the CT meter plugged into the multiplus-II-GX. Unfortunately it is still not reacting to either DCL = 0a or DCL with any value. I have rebooted and powerecycled all of the devices however the behaviour in mode 3 seems consistent with the behaviour in mode 2.

Any thoughts?


Regards,


Mike Christiansen.


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Hi @nzmikec

For ESS mode 3 I've updated the documentation, it indeed does not listen to DCL, your control algorithm should do that.

ESS mode 2 is much easier, and -should- listen to DCL=0, if not, please reply to the email I sent so we can have a closer look at your system.

https://www.victronenergy.com/live/ess:ess_mode_2_and_3#mode_3

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steve-3 avatar image
steve-3 answered ·

Hi @nzmikec,

Did you end up resolving your issue with the Batrium BMS, I'm having the exact same problem now after I changed the ESS mode to 'optimized with battery life' from 'optimized without battery life'. I ended up putting it back to 'without battery life' and had all kinds of dramas with the Multiplus not charging at all and not responding to any BMS commands. After lots of trying different things have got it to the stage that it will respond to the charging commands, but no discharging. Unlike your issue the DCL doesn't change when I adjust it in the Batrium software, can see it change the CCL. I've had it running almost perfectly for the last 6 months, and was trying a bit of tweaking basically to see what the different settings do, re-learning the old adage, if it aint broke don't fix it.

Setup: Batrium Watchmon 4 v4.15, CCGX v2.60, Multiplus II 48/5000/70 v482.

Any help would be much appreciated.

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Hi Steve,

My issues ended up being that I was expecting the ESS system to follow the commands from the BMS when in ESS Mode 3. At the time the ESS manual did not advise that this would be the case but since that time the documentation has been corrected.

To your point you seem to be either in ESS mode 1 or 2 so as far as I understand the system should respond to the BMS. Is the communication working? Can you see your BMS in the device list and are the the charge / discharge rates showing under preameters? Pic for reference. screen-shot-2021-07-19-at-94241-am.png

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steve-3 avatar image
steve-3 answered ·

Hi Mike,

Thanks for your response. Yes communicating and can see parameters in remote console;

bms-parameters.png

When I go into Batrium software and turn off charging and discharging manually under the control logic tab, only the CCL changes as below;

parameters-after-turning-off-charge-and-discharge.png

It has been working well previously until I changed that 'optimized battery life' setting, maybe it changed the ESS mode? How do you tell what ESS mode it's in?

Also as bit of a background, when it stopped working after I played with the 'optimized(with battery life)' I updated the firmware in the CCGX to see if that fixed it, but made it worse. It was then not responding to either the charge or discharge commands. So rolled it back to the previous firmware and then went back to the current situation.

Regards Steve


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simjoc avatar image
simjoc answered ·

Dear Steve,


Did you fix the problem? Or are you staying at the old situation? I've the same problem, but Victron not listening to the charging commands from batrium.


Small edit: it works perfect with dc powered feed in disabled.


Simon

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David avatar image
David answered ·

With DC feed in enabled, my Batrium / Victron system will overcharge the battery and go over the voltage and current set by the BMS. I have tried everything to fix.

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gjones84 avatar image
gjones84 answered ·

Hi All,

Ive been running a batrium WM4 with my Multiplus in mode 2 'optimized with battery life' and the DCL and CCL always worked.


Ive recently decided to switch my ESS to external contol and run mode 3. My control loop works a treat. However the other night I was horrified to see that DCL change to 0A and my inverter continued to discharge :(. My low cell cut off is 3.4V and on cell ran down to 2.8V and operated my shunt trip.

Why doesnt mode 3 listen to DCL? Can Victron add this to their next firmware update pretty please?


Thanks

Gareth

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gjones84 avatar image
gjones84 answered ·

Hi All,


Did anyone ever come to a fix for this? DCL and CCV ignored when is mode 3.


ATM im using HA to look at the cell voltages and stop inverting and charge depending on certain thresholds. I dont like relying on HA for BMS functions.


Ive recently had a though of using the Venus OS Large image using node red connected to the multiplus and sniff the canbus network to extract the min / max cell voltages and stop inverting or charging if they get too low or high.


I was thinking of using MQTT but you do rely on your home network. CANBus would seem like the most robust comms for this functionality.


What do you guys think?


Cheers


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