question

philipl avatar image
philipl asked

Solar First with Multiplus II

I have a setup with 3 X Multiplus II's running in parallel, 450/100 MPPTs, solar panels and pylontech batteries.


The batteries drain to 20% during the night and the solar panels are sized so that at around 2pm in the day the batteries are fully charged again.

What happens in the morning is that for the first two hours or so, the system charges the batteries and uses power from the Grid for the AC loads. This is completely unnecessary, the solar power early in the morning should be used to power the AC loads and not to charge the batteries.

How can I change it so that the solar power first thing in the morning is used to power the AC loads, and not to charge the batteries?


There will be plenty of time later during the day to fully charge the batteries.


Thank you



VRM
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16 Answers
shaneyake avatar image
shaneyake answered ·

This is correct operation of ESS. There is a 5% hysteresis in the system. This is there to prevent the battery from being constantly cycled in cloudy/ bad irradiance conditions.

If you would like to change this behavior, you can but you will need to do it via NodeRed or some other type of external control. I have a few sites running what I call soft start, where the system will gradually move the loads over to PV as more PV becomes available.

This way battery will be held at minimum SOC and if a cloud blows over the inverter will throttle down to not run off the battery. This happens until minimum SOC+5 and then the system runs normally.

To do this you will need to install the large firmware and setup NodeRed to do ESS control.
This is an advanced feature and will have a decent learning curve.
https://www.victronenergy.com/live/venus-os:large

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Paul Test avatar image
Paul Test answered ·

@kevstone122

agree with you :-)

the ess system need some more configurable parameter to work alone and as many users wont.

let's deside the user about AC-Load or battery first at sunrise......

regards

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checkit avatar image
checkit answered ·

@philipl MPPTs will always charge the batteries first. If you need AC loads to take priority from solar, a grid-tie inverter would be the best solution.

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shaneyake avatar image shaneyake commented ·

The all multiplus inverters are Hybrid inverters, this means that they can run as a grid-tie inverter or as an off-grid inverter. Yes, MPPTs are putting power onto the DC bus but that doesn't mean it has to go to the Batteries, it can be used by the inverter straight away.

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checkit avatar image checkit shaneyake commented ·

I was referring to a grid-tie inverter such as a Fronius or SMA...


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shaneyake avatar image shaneyake checkit commented ·
Yes, I understand but why is a grid-tie a better solution when a hybrid inverter can run loads from solar first or even do a soft start so it covers as much of the loads as it can from solar and the rest comes from grid?
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kalito avatar image kalito shaneyake commented ·
PV inverter is powered by PV and outputs AC. It ref the grid to operate and needs no batteries.
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muddy1 avatar image
muddy1 answered ·

You need to look at Victron's energy storage info.

https://www.victronenergy.com/search/?q=self+consumption

You will need to install an ESS assistant onto the Multiplus. You may need an energy meter depending on your system setup.

Then set the battery state in the ESS to "self consumption".

The ESS gives you get further options on the Venus controller. Here you can set times for batteries to charge.

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kaycegivens avatar image kaycegivens commented ·

Thanks for the detailed reply.

slope game

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philipl avatar image
philipl answered ·

Hi,

I have not been able to get this to work. The system is already set to self consumption but it stil uses power from the solar panels in the morning to first charge the batteries for an hour or two.

Can someone please give me some specific details on how to try and change this.

Thank you very much.

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philipl avatar image
philipl answered ·

I think I have an idea of what it may be. Under settings, ESS, Mode is set to "optimized with battery life"

Minimum SOC and Active SOC was set to 20%, but then after a while the system sets active SOC to 25%. That may be why the system is charging the batteries first thing in the morning. I will now set it to "optimized without battery life" and see if it makes a difference.

The batteries are fully charged every day by around 12 or 1pm, so there shouldn't be any reason to raise the active SOC.

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philipl avatar image
philipl answered ·

I changed to optimized without battery life and set SOC to 20%, but again this morning, the first 1.5kwh that was generated by the PV panels went to charge the battery, and at the same time 1.5kwh was pulled from the grid to power the AC loads. So this is still not working.

Does anyone have more details or suggestion on how to program the system so that Solar power is ALWAYS used FIRST to power AC loads, and only then if there is power left to charge the batteries?

Thanks

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Matthias Lange - DE avatar image Matthias Lange - DE ♦ commented ·

At what SOC are the batteries in the morning?

As far as I know if the SOC falls 5% below the set SOC limit (due to self consumption of the components) then recharging the batteries back to the set SOC limit as fast as possible has the highest priority.

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shaneyake avatar image shaneyake Matthias Lange - DE ♦ commented ·

If the SOC drops below 5% of the minimum SOC then the inverter will charge from Grid back to minimum SOC.

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Alex Rodgers avatar image
Alex Rodgers answered ·

Have a similar problem, got around it by installing a contactor on the inverter ac supply - controlled via one of the relays - on the MPPT, inverter or CCGX/Venus

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shaneyake avatar image shaneyake commented ·
You don't need to do this. The inverter is fully programmable. You can just setup a rules to make this happen. At the very least you can just use an AUX input on the inverter to trigger grid disconnect and the best you would just disable feed-in via Modbus/MQTT or NodeRed
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mcmahan-renea avatar image
mcmahan-renea answered ·

i have the same question like you! snow rider 3d

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tnt369 avatar image
tnt369 answered ·

Is "Scheduled charging" active in the ESS settings (lowest menu item in ESS)? During the period of scheduled charging, the load is supplied from the mains.

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Rob Fijn avatar image
Rob Fijn answered ·

If you are not using the ESS there is the Virtual Switch you can use to ignore the AC input. You can use the AC input again based on a condition you can set, this can be voltage but also SOC.

Rob

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kevstone122 avatar image
kevstone122 answered ·

Hello Together!

I totally agree with the problem of Philipl. Also in my opinion this makes no sense, but nobody understand it correct!

The problem is not the SOC Level or this 5% Hysteresis.
It's okay if during the night the Batterie stops at 20% and in the morning it should be charged to 25%...
BUT the Problem is, if the AC Loads are higher then the Solar-energy!
For example:
Solar 2kW, AC Out 4kW.
So the Batterie is charged to 25%, Multiplus switch to inverter mode and the 4kW are comeing from the Batterie. The Grid has in this time nothing to do!
But because of only 2kW Solar Energy, the Batterie will reach again the 20%. Then Inverter Stops again and repeat it. The Full Solar Power will be used to charge the Batterie to 25% and all the 4kW are used now from the Grid...Why??? We reach 25%, after this discharge to 20%, again again again. This makes absolutely no sense! Why i should charge the Batterie, and don't use the energy direct for the house!
I understand the Problem, because at the end of the day this is correct. So System will assist the AC-Out always from the Batterie. For this we have the Batterie. But the start in the morning is an different Situation! We cannot put any energy from Solar to the Batteries, before the Solar is higher then the ACOut.

FIRST must be the AC Output, so the internal LOADS from the House are used from Solar Power. If i have 4kW in the House and 2kW from Solar, i can use 2kW from Solar and 2kW from Grid. 0 Ampere from Batterie. Why we need to charge Battery?
If the Solar Power will reach for example 5kW, then we can use 4kW for house, 1kW for charging!
This means the Start-up procedure during the morning is wrong in my eyes.

I understand it's difficult to descripte and change software but i have 2 ways:
-Maybe can we adjust somehow the 5% Hysteresis? So If we maybe just use 10%, then the SOC Limit need to reach a higher level and batteries have more KWH saved, then we can start to use the Batterie during Solar Power goes down. So we can adapt for each System, depending on their output level!
-Best Idea would be to block charging in a time window. The same like the "planned charging" i want an "planned blocked charging" . If i can just block the charging until 10 o'clock in the morning it will be fine. Or just block charging if Solar Power is not higher then 5kW....If its 4kW, then it should run into the AC Out and not in the Batteries!
This value need to be adjusted to the "Standby-Power" from each house. If the Standby is 1kW, then we never start charging before 1kW Solar Power!

For me is this problem really important. Please take attention!
Best regards
Kevin

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shaneyake avatar image shaneyake commented ·
The way that this can be down in software is to change the control mode.

Normal ESS is trying to hold a grid setpoint but once we hit min SOC the mode should change to hold battery setpoint. This can be done with a PID and you can put a limit on the PID which is the grid setpoint.

At night system changes to hold battery at 0W.
When the sun comes up all PV power is used to run loads, once PV power gets the grid to 0W then extra power is used to charge battery, once battery is 10% above min SOC then system returns to Normal ESS till min SOC is hit and mode goes back to battery hold.

I have implemented this in NodeRed and it works really well.

This is purely dynamic and can be used on systems of any size with any load. Doesn't need you to program in any times or other configuration.

@mvader (Victron Energy) Can this be added at some point? Maybe call it ESS with soft start.

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Manda avatar image
Manda answered ·

I have Multiplus I (the old one) + pylontech + cerbo : with default settings, loads are always powered in priority, regardless the SOC (thus I set the min SOC to 10%). If PVPow > Load, batteries are charged with the difference, otherwise, the difference is drawn from the batteries. I (manually but this should change soon) connect to grid only on very cloudy-rainy days, and in such a case loads have always the priority. I also manage a 1200W water heater with Nodered (rpi 4) and Tasmota, so that the heater never uses energy from the batteries or from the grid.

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shaneyake avatar image shaneyake commented ·
You are running off-grid most of the time which means that you aren't using ESS.

Disconnecting from grid is not a real solution.

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kevstone122 avatar image
kevstone122 answered ·

So how we can solve this issue? Is there any Bug-Fix planned?

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kevstone122 avatar image
kevstone122 answered ·

Do we have any solution?

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Pat avatar image
Pat answered ·

Fascinating discussion. Very interesting. I may have problems and not even know it.

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