question

murphy-r avatar image
murphy-r asked

Multiplus 12/3000 + Cerbo + Lynx BMS + Smart Battery DCVV

Hi I am expanding an older system with the following components and ran into behavior by my Multiplus 12/3000 in charging my new Victron Lithium Smart batteries.

Components

  • Cerbo GX
  • Lithium Smart Batteries
  • Lynx Smart BMS
  • Multiplus 12/3000

I see in the Cerbo where the Lynx communicated through DCVV the following values from the battery.

  • CVL - 14.2V
  • CCL - 330A
  • DCL - 600A

However, when I start commissioning the first battery solo the Multiplus is charging at 13.8V and floats at 13.38V

So a few questions:

  1. Does my Multiplus on the latest firmware v494 support DCVV over the VE.Bus?
  2. When I go into the configure the Multiplus it specifically says in the help section that if a Lynx BMS is used the GX will override all settings over CAN-bus
  3. Trying to understand why the Multiplus is charging at below 14.2V even when I configured it to do 14.2V if the DCVV was not working.
  4. My Multiplus dropped into float after 15-20minutes on the single battery and never hit a voltage above 13.8V to trigger the batter to know it's cell status. Not sure how to get the cell status to calculate. Battery Cells are all 3.40V and says Battery Read For Use in Victron Connect App.
  5. For a fully charged 12V Victron Lithium Smart Battery what is the normal cell voltage supposed to be?

Cheers!

cerbo gxBMSmultiple inverterssmart lithium
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

3 Answers
Stefanie avatar image
Stefanie answered ·

Hi @murphy_r,

Settings look ok except for the MultiPlus charger settings:

  • Lithium Battery: Off (Not sure I should turn this on if BMS is lost) - Yes this need to be turned on. If turned off, the charge algorithm "thinks" a lead-acid battery is connected. This will automatically turn on temperature compensation, which I think is causing the problem. Lithiums don't need temperature compensation.

  • Absorption Time: 8h - Make this 2 hours so that it matches DVCC settings of your Lynx Smart BMS.

  • Charging at about 0.25C any idea how long absorption phase should be? - see above. However, the Multi will always remain either in bulk or in absorption. But since DVCC controls the voltage targets (14.20V and 13.50V) and not charge phases, this is not a problem. With lithium, we no longer talk about charge phases. The question should be: How long does the multi charge at 14.20V before it ramps down to 13.50V. If everything is set correctly, it takes exactly 2 hours as set in DVCC and MultiPlus charger settings.
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Stefanie avatar image
Stefanie answered ·

Hi @murphy_r,

1. Yes, the MultiPlus is DVCC compatible and receiving CVL, CCL and DCL from your Cerbo GX.

2. That is correct. In a properly set up system, the GX unit overrides the charger settings in the MultiPlus. However, it is a good idea to configure the MultiPlus charger with the same battery limits (14.2 V absorption, 13.5 V float) as a precaution, just in case communication get lost.

3. More information is required. What are the exact settings for your MultiPlus? Any images and/or a wiring diagram of your installation? Are you 100% sure the Cerbo GX is communicating with the MultiPlus? A quick check could be to disconnect one of the BMS cables from the Lynx Smart BMS. This will trigger an alarm situation that should shut down the MultiPlus.

4. Cell voltages are not reported to the MultiPlus. This works via target voltages (14.20V or 13.50V), depending on the SoC threshold set in the Lynx Smart BMS. Please also post your Lynx Smart BMS settings.

5. 14.20V / 4 = 3.55V per cell 13.50V / 4 = 3.37V per cell

I wouldn't worry too much about seeing 13.38V in float. It depends on when exactly this measurement was taken. But 13.80V absorption is definitely not correct.

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

murphy-r avatar image
murphy-r answered ·

Stefanie,


Item #3: Yes I manually configured the Multiplus with the following

  • Charger Settings
    • Charge Current 90A (Limiting this value with a single battery)
    • Absorption 14.2V
    • Float 13.5V
    • Repeated Absorption Interval: 14d
    • Repeated Absorption Time: 1h (I believe I need to change to 2h)
    • Absorption Time: 8h
    • Charge Curve: Fixed
    • Lithium Battery: Off (Not sure I should turn this on if BMS is lost)
    • Storage Mode: Off
    • Use equalization: Off
  • INVERTER
    • DC Low Input: 11.2V (Thinking to change to 12.4V at ~90%)
    • DC Input Low Restart: 12.8V
    • DC Input pre-alarm: 12.8V (Not sure if I should lower this to say 12.6V)
    • AES: Off

Lynx Smart BMS Settings:

  • System Settings
    • Battery Capacity: 330A (due to single battery connected for initial commissioning)
    • Number of Batteries in Parallel: 1
    • BMS Pre-alarm: Enabled
  • Relay Settings
    • Relay Mode: Alarm Relay
    • Alarm Relay: Intermittent
  • DVCC
    • Discharge Current Limit at Pre-Alarm: No
    • Absorption Time: 2h 0m
    • Repeated Absorption Interval: 30d
    • SOC Threshold 70S%
  • Battery Monitor
    • Charged Voltage 14V
    • Tail Current: 4%
    • Charged Dection Time: 4m

So far this is a multi-phase implementation. The only thing hooked to the Lynx Distributor is the Multiplus.

Test of disconnect BMS cable in chain while charging with Multiplus. I tried this and Multiplus was stayed in absorption phase. One note that the multiplus does have the external panel configured with the on/off/charge switch.


diagram.png

I got 3 out of 4 batteries to say fully charged and balanced. Got the 4th one to do.

Charging at about 0.25C any idea how long absorption phase should be? Going on over an hour and I don't have a good perspective how long to expect the multiplus to take to get from absorption to float. Given that the battery says fully charged on Victron Connect not sure why the Multiplus is still in absorption phase and not moved to float through DCVV.

Really appreciate the feedback as I slowly ramp up my knowledge on the new batteries and monitoring systems.


Cheers

Robert


diagram.png (753.7 KiB)
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.