Active BMS, MultiPlusII, How to stop Charging...

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Bernhard Matschinger asked Jul 19, '19

Active BMS, MultiPlusII, How to stop Charging...

Hy all!

I read hundreds of pages, but it seems i haven't found the right answer.

I have a 3 Phase MultiPlusII 48 3000 35 System, with AC Couppled 5kW Inverter, an DC couppled MPPT and a DIY 48 V 260 Ah Battery Bank with active BMS.

-- this picture shows the system with battery Cut Off...,

My Problem is, that the Active BMS has no interface to any System, so I used an RaspberryPi, read the "Console" and write to the Colour Control GX via Modbus some data like SOC.

I even tell the MPPT and the PV inverter to stop Charging, when the System is in Island mode (ModbusTCP).

BUT.. when the Grid is connected, I can not tell the MultiPlus to use all available Energy to feed back to grid until the BMS shuts the Relay off itself ...

I am able to stop Charging the battery, but then the Multi does not use any power from the Battery ???? and I can tell the MPPT to stop working (all done via ModbusTCP)

My question is:

Can I stop Bulk and floatcharging via ModbusTCP? or do I have to make different settings?

The System knows the SOC, and i do not need any constant current. and so on.

Important: there is an active BMS. it shuts it's relay off when 100% is reached. no overshooting, no burning energy..

What I want is, that

when charging, and the soc is > 95 % the Charging Power to the battery should be reduced to 0 when 100 % is reached.

all access Power should go back to the grid.

when there is no grid, the Chargers should reduce themselves to 0

Please give me some Info / help

Multiplus-II MPPT Controllers BMS ac coupling

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Bernhard Matschinger answered · Jun 06, 2020 at 07:16 AM

This question is solved by implementing CAN Bus Feature to the SYSTEM.

The BMS is controlling the ESS System via CAN

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alfonsohera commented · Jul 24, 2020 at 07:50 AM

@Bernhard Matschinger Did you manage to stop charging completely just via the charging current limit sent via CAN? In my system my Multiplus remains in Bulk mode and keeps charging the battery, although with a small current (less than 1 A) even if the CCL is sent with 0. Using the Aux contact and configuring it to allow/not allow charging depending on its state would of course solve this issue but I was wondering if it is possible to control it just via CAN.

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Answer 1 · 2019-07-19T16:07:31Z

wkirby answered · Jul 19, 2019 at 04:07 PM

I have a DIY battery bank and DIY BMS. I use the "Two Signal BMS Assistant"
I use opto isolators on my BMS to interface directly with the MultiPlus to stop charge or discharge. Dry relay contacts will work just the same.

You did not mention if you are using ESS? I use ESS and the BMS condition to stop charge affects the MPPT's too. Charging completely stops when the "Stop Charge" signal comes from my BMS.

This is a description of the "Two Signal BMS" Assistant:

I wonder if this will make the interface between your BMS and Victron system easier? Perhaps it would be even safer since it is simpler and does not rely on an external CPU based system (RaspberryPi) to keep running.

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Answer 2 · 2019-07-20T13:27:24Z

Bernhard Matschinger answered · Jul 20, 2019 at 01:27 PM

Hy @WKirby!

thank you for your information.

I am using ESS for now, and want to use it later on as well

I will try this.

When looking at the wiring diagram i get some questions.

I have to use the Aux 1 (and Aux 2 for a second "Parameter"). So my question is: do I pull them to Ground or up to 5 V to get the wanted affect. ..

When Aux1 relay is open, charging should be disabled

When Aux2 relay is open, discharging should be disabled

--> so to get a "closed" Relay state to the Aux.. do I have to pull it to Gnd or to 5 V (12V)...

many thanks for your help

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