question

untainsyd avatar image
untainsyd asked

Minimal Victron System Design for Backup Power

Hello, I'm seeking assistance in designing a Victron backup power system with minimal expenses. Due to ongoing blackouts in Ukraine, I need a reliable reserve system. Despite extensive research on Victron products, I still have several questions.

Here is my possible design, I would like you to edit/review it:

1720024971564.png

Proposed System Components:

  • Victron Energy MultiPlus-II 48/5000/70-50
  • Lead-Acid Traction Batteries (currently 10.6 kWh, plan to upgrade to lithium in the future)
  • BMS for lead-acid batteries (to be determined)
  • Lynx Distributor or Power In
  • Cerbo GX

Questions and Concerns:

  1. Battery Monitoring: Can the MultiPlus-II inverter monitor discharge/charge thresholds of 48V lead-acid batteries connected in series?
  2. BMS Requirements:
    • Is a BMS necessary for lead-acid batteries?
    • If yes, which BMS would you recommend?
    • Can the MultiPlus-II communicate directly with the BMS to determine charge/discharge thresholds?
    • Where should these thresholds be set: inverter, BMS, or both?
  3. Lynx Shunt VE.Can: What is its purpose? Does it replace the BMS?
  4. Configuration for Lead-Acid Batteries:
    • How to configure the MultiPlus-II for lead-acid (traction) batteries?
    • Should configuration be done via Bluetooth or VEConfigure program?
  5. Can i temporarily operate without Gerbo GX, and add it in the future?
Multiplus-IIvictron productssystem designlead-acid
1720024971564.png (84.9 KiB)
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

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

3 Answers
Alexandra avatar image
Alexandra answered ·

No bms needed for lead acid.

The lynx shunt does the same thing as a BMV.

The batteries you choose should have a datasheet so use those for values to charge to.

If using a multiplus 2 you need an mk3.

Every part needs to be programmed. The mot and bmv 712 can be done over Blue tooth.

You need the cerbo if you want to use ESS, but if you are only connection to grid to charge then not really.

Bmv 712 has midpoint monitoring but you should look at balancers as well. And rotate the lead acids around.

1 comment
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

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

andrii-podanenko avatar image andrii-podanenko commented ·
If you have 2*12V = 48V system designm then Balancer is neccessery.
2 Likes 2 ·
Alex Pescaru avatar image
Alex Pescaru answered ·

Several Ukrainians here who can help you with the system design.

One of them is @Andrii Podanenko

You can contact him and share impressions.

1 comment
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

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

Alexandra avatar image Alexandra ♦ commented ·
Get the lynx power is the distributor uses power from the Lynx shunt to work the lights and are generally not needed.
0 Likes 0 ·
andrii-podanenko avatar image
andrii-podanenko answered ·

Finally found a time to respond.

  1. Battery Monitoring: Can the MultiPlus-II inverter monitor discharge/charge thresholds of 48V lead-acid batteries connected in series?

I'd recommend you to get 4*12V balancer, just in case the AGM got different params over the time, which will destroy it faster than needed.

MultiPlus-II will work just fine with 48V AGM, it'll treat it as just a single battery, without any monitoring of every 12V item. Charger there should be configured respectively, via VE.Configure app


  1. BMS Requirements:
    • Is a BMS necessary for lead-acid batteries?

If you want them to last - sure it is needed

  • If yes, which BMS would you recommend?

Any 4x12V - the larger current they can use for balancing - the better results you'd get

  • Can the MultiPlus-II communicate directly with the BMS to determine charge/discharge thresholds?

Not needed for AGM, basically. I didn't see any 2*12V BMSes , compatible with VenusOS

  • Where should these thresholds be set: inverter, BMS, or both?

Balancer will take care about equalisation, inverter/charger about thresholds


  1. Lynx Shunt VE.Can: What is its purpose? Does it replace the BMS?

It is needed for proper SOC measurement, as well as it has capability to monitor fuses on Lynx Distributor. Usually needed when you have couple of battery banks in parallel and want to properly measure SOC for your setup. Also it should be better calibrated, if I remember it right.


  1. Configuration for Lead-Acid Batteries:
    • How to configure the MultiPlus-II for lead-acid (traction) batteries?

You need to use VE.Configure app with MK3 cable ( if no cerbo gx ). If cerbo gx is in place - you may configure it via VRM + VE.Configure. There is a predefined config for AGM in VE.configure, just set Ah volume of your battery there

  • Should configuration be done via Bluetooth or VEConfigure program?

MultiPlus-II has no BlueTooth, unless you get Bluetooth dongle. Not sure if you can set everything via it. You'd need to configure it via VE.configure to get to all settings

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

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

Related Resources

MultiPlus-II Product page 

MultiPlus-II Manual

Multiplus-II GX Online Manual

MultiPlus-II 230V Datasheet 

VE.Bus Error codes

Additional resources still need to be added for this topic