Multiplus II charges battery from main too

DIY
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1

Hi all,

I have following situation:
Multiplus II connected to grid via AC IN, 1 phase
MPPT, Cerbo, VM-3P75CT
Pylontech battery
ESS Optimized without Battery Life
Min SoC 13%

Actual behavior:
Multiplus charges the battery even SoC is far over 13%, no matter if MPPT power is there or not.

Desired behavior:
Multiplus charges battery only if SoC <= 13%, at first with MPPT power (if available), then with grid power.
Over 13% it should never charge the battery via Multiplus except I want it explicitly (e.g. charge boat battery with shore power or I have a tariff with cheap “slots”)

I can’t use “Inverting only” because Multiplus is connected on AC IN and even it were on AC OUT then I wouldn’t be able to charge because nothing is connected on AC IN, so no grid power.

At the moment I have node red in place with some “experimental” stuff to prevent charging. This works more or less. (I got the feeling the ESS has its own brain and ignores my settings)

     (just inverting, no need to charge battery via grid)
     If SoC > 13% => Multi On, Charger Off {
            setting Multiplus /Dc/0/MaxChargeCurrent = 0
            setting ESS Multiplus "Disable charge" = 0 
     }

     next part is the night part, when the battery is sucked out and there is no PV power
     If 10% < SoC <= 13% => Multi On, Charger Off {
            setting Multiplus /Dc/0/MaxChargeCurrent = 0
            if not enough PV voltage {            
                  setting ESS Multiplus "Disable charge" = 1 (MPPT can't charge too)
            } else (in the morning, PV comes slowly, turn on charging to fill the battery with MPPT) {
                  setting ESS Multiplus "Disable charge" = 0
            }
     }

     ("recover" battery)
     If SoC < 10% => Multi On, Charger On {
            setting Multiplus /Dc/0/MaxChargeCurrent = 50
            setting ESS Multiplus "Disable charge" = 0
     }

@victronenergy: I need a multiplus mode: inverting, no charging except an “absolute min” SoC is reached then charging to “min” SoC
What I don’t understand why the system doesn’t use PV power, satisfies its loads and the excess is stored in the battery. Most of the times it charges the battery - no matter what SoC - and the excess is for the loads.

Ideas are very welcome!
Thanks
Sven

2

Here you go. I do some similar stuff but use DVCC which controls the current of the internal charger and if the MPPT is charging the total current is the sum. So if there is 20A from the MPPT the internal charger will supply an additional 30A to get to 50A or if you set DVCC to 70A the internal charger will boost to 50A to make the 70A of charging if that makes sense. If you set the current low 10A for example it will use the MPPT power first.

The function will charge if the SOC is 10% up to 13%. This should get you started if you need more help let me know.

I have the JSON code in a text file if you want to try it.

image
image1219Ă—589 76.5 KB

CHECK SOC AND CHARGE.txt (9.4 KB)

3

Thanks a lot.
I had a similar solution before but it didn’t work.
Our solutions are not working when ESS #1 is triggered, then the systems charges the battery even the maxCurrent is set to 0.
Just seen: Min SoC 13%, current SoC 14% or 15%, charging (ESS #1). Apparently it’s not a sharp 13% min SoC, I try to set it lower, so I will end around 10-12% .

I modified your solution, use the MPPT voltage and not the power because the voltage is always there even if it’s not charging. Power is only available, if it’s allowed to charge so current can flow.

4

Are you saying adjusting DVCC to 0 does not disable the charger? You could write DVCC with the output of the MPPT charge current. That would only use solar. Are you using a grid meter with any grid-tied AC inverters?

What I do is set a min charge current I want based on a typical drawdown. If I need the battery 100% and its 50% 400AH then I need 10hrs of charge at 20amps to put in the 200AH missing. This seems to work and I could add a formula to set the min current over 10hrs to charge the battery but have found I dont need it.

5

Yes, setting it to 0, doesn’t stop the charger.
No there are no other inverters.

6

That is so weird I have never had that. DVCC is the best tool for ESS. I use it in at least 3 different flows. There must be a setting incorrect somewhere.

7

I will monitor the installation and report further abnormalities :grimacing:

8

You have enabled it in the settings?

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image1318Ă—777 117 KB

9

Yes it’s “Forced on” because of the BMS
It’s set to 1A, just to play around at the moment

image
image4190Ă—2422 507 KB

10

If ESS #1 is enabled (~1-2 higher than min SoC) and max current is set to 0A (min SoC 12%, current SoC is 13%) then the MPPT will not start.
When I set it to maybe 20A manually then the MPPT starts.

It’s so confusing.

Btw I have the latest firmware for all devices.

11

What is the sustain and dynamic cut off in ESS assistant set to?

You can disable the internal charger with a combination of the charge current control assistant and a relay.

12

Sustain 48V, dynamic 46V

13

If you are using communication from the battery, I can’t help you. It’s impossible to know what the battery requests or asks the system to do.

14

If the system reaches the cut-off voltage it starts recharging to the sustain voltage not matter what the SOC is.

If you didn’t reach 100% for a longer time the SOC reading will drift off more and more and doesn’t match to the voltage reading.

1 Like
15

I’ve mitigated it that way:

let PV = 0;
let SoC = 0;
if (msg.topic == "PVPower") {
    PV = msg.payload
} else if (msg.topic == "SoC") {
    SoC = msg.payload
} 

if (SoC > 12) { 
    msg.payload = 5000;
} else {
    if (PV > 100){
        msg.payload =  PV - 100;
    } else {
        msg.payload = PV;
    }
}
return msg;

It’s a little bit dirty but it works so far.

Thanks for your contributions!