question

blackmarlin avatar image
blackmarlin asked

MPPT power is limited for DC feed in if battery is full

Setup:

MultiPlus-II 48/3000/35-32 / FW: v501
BlueSolar Charger MPPT 150/35 rev3 / FW: 1.61 with 2kWp solar panels
GX Device / FW 2.92
48V CAN Battery connected to the GX device
EM24 Ethernet smart meter
PV inverter at AC IN


I have configured ESS with DVCC for the system. As long as the battery is charging, the MPPT provides full power (even if battery takes less power than the MPPT provides). But as soon as the battery is full and the excess power shall be feed in to the grid, the power of the MPTT is limited (about the half of the theoretical available PV power.

Battery is charging (MPPT DC power is 1021 W):

1676207596189.pngBattery is no longer charing (MPPT DC power is limited to 602W)


1676207577281.png


Do you have any suggestions?

Best regards

Michael


This is my configuration:

DVCC

1676207231881.png

1676207252869.png

ESS

1676207285462.png

1676207297642.png

1676207308988.png


MPPT ControllersESSDVCCfeed-in limit
1676207231881.png (23.8 KiB)
1676207252869.png (24.7 KiB)
1676207285462.png (25.2 KiB)
1676207297642.png (21.8 KiB)
1676207308988.png (18.7 KiB)
1676207577281.png (65.7 KiB)
1676207596189.png (68.6 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.

19 Answers
nickdb avatar image
nickdb answered ·

Any input current limits set on the gx or inverters themselves?

2 |3000

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

blackmarlin avatar image
blackmarlin answered ·

No limits set.

2 |3000

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

blackmarlin avatar image
blackmarlin answered ·

I experimented with some DVCC settings. If I activate SVS - Shared voltage sense, the MPPT DC power goes directly down to about 50W. SCS - Shared current sense seems to have no impact to the behavior in my configuration.

Any ideas?

It seems to me that this thread from 2019 is describing the same issue: https://community.victronenergy.com/questions/22506/ess-ac-dc-coupled-feed-in-excess-solar-charger-pow.html

Best regards

Michael


1 comment
2 |3000

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

nickdb avatar image nickdb ♦♦ commented ·
What battery is this? Is it configured as the reference in the gx system setup? Does it send cvl limits etc?
0 Likes 0 ·
blackmarlin avatar image
blackmarlin answered ·

It is a SEPLOS BMS and it does send parameters via the CAN bus.

If the battery is full, the CCL is send with 0A obviously. But this should be ignored by the MPPTs as DC feed-in is configured active and the MPPTs should provide 100% power.


1676227322447.png


1676227322447.png (16.8 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.

marekp avatar image
marekp answered ·
2 |3000

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

blackmarlin avatar image
blackmarlin answered ·

This seems to be a problem that affects some people:

https://community.victronenergy.com/questions/175803/mppts-switch-off-when-soc-is-getting-colose-to-100.html

https://community.victronenergy.com/questions/22506/ess-ac-dc-coupled-feed-in-excess-solar-charger-pow.html

Does the voltage difference between the absorption voltage (55,2V in my case) and float voltage (54,4V in my case) of the battery limit the max. MPPT DC feed-in power?


Best regards

Michael

2 |3000

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

vicens avatar image
vicens answered ·

Yo probaría de poner la flotación del inversor mas bajo que la flotación del mppt, medio voltio por ejemplo.

2 |3000

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

astrayan avatar image
astrayan answered ·

What happens when you turn off the PV inverter? I notice on the second screenshot, the grid voltage is a bit higher on L1 and L3

2 |3000

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

pedaaa avatar image
pedaaa answered ·

you should turn ON, the visibility of the Multis:

at settings -> system setup -> battery measurements:

1678171012319.png


then the multis are shown in VRM like this:

1678171079374.png


this might help to see, what the multis are actually doing.


Also it would be good, if you can read Modbus.

At Register 791, ID100, you can see, if the MPPT is actually throttled or not. (maybe there is just lack of sun power?)

Register 791:

Status 0 = MPPT is OFF

Status 1 = MPPT is ON, running throttled

Status 2 = MPPT is ON, running without limits



1678171012319.png (29.4 KiB)
1678171079374.png (46.4 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.

blackmarlin avatar image
blackmarlin answered ·

@Vicens I tried to set the voltages higher in the MPPT configuration. But as I have enabled DVCC this has no effect. The charge voltage of the MPPT is set automatically 0.4V higher than the charge voltage configured in DVCC by the victron system. Probably this is exactly to allow grid feed in, but is not sufficient in my case.

MPPT

1678539461742.png

@Astrayan I can see no difference if the PV inverter is disabled.

@Pedaaa

Here you can see a screenshot where the sun is shining very bright. MPPT solar power should be around 1500W instead of 618W.

I checked the Modbus register 791 (but with ID238 for the MPPT) and as long as the battery is charging, the status is:
2 = MPPT is ON, running without limits
As soon as the battery is full, the status changes to:
1 = MPPT is ON, running throttled

Why could the MPPT be throttled in this situation?

Best regards

Michael

1678539850623.png



1678539461742.png (29.1 KiB)
1678539850623.png (75.1 KiB)
1 comment
2 |3000

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

pedaaa avatar image pedaaa commented ·

hard to tell.... mhhh.. maybe your BMS is requesting some special Charge-Limitation or similar?!


Maybe you can try, to disable the BMS controlling your MPPT?!

in this video, you can see how this could be done:

https://youtu.be/tSi-VdI3Ah4

0 Likes 0 ·
astrayan avatar image
astrayan answered ·

OK. The screenshots you have provided show a maximum of 84W going from PV Charger to Grid. What's the largest number you can contrive?

1 comment
2 |3000

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

astrayan avatar image astrayan commented ·

Just wondering if the multiplus is just bad at putting power to the grid.


0 Likes 0 ·
Marcin Mocydlarz avatar image
Marcin Mocydlarz answered ·

I have the same problem.

https://community.victronenergy.com/questions/161792/mppt-limit-charge-power-instead-of-exporting-to-gr.html

When SOC is close to 100% then MPPT limits powet instead to feeding to the grid. It started when i have connected Fronius PV. My workaround is limiting charge power when charging state switched to absorption. Limiting charge in ESS menu to 0W, then it works fine. You have to disable dvcc to limit charge power in ess menu;/ I have custom script for this but you can use node-red from Venus OS Large. Until I found a solution, I was losing about 20% of PV energy...

2 |3000

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

blackmarlin avatar image
blackmarlin answered ·

@Astrayan I don't understand what you mean with 84W to the grid?

1 comment
2 |3000

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

astrayan avatar image astrayan commented ·
I'm uncertain of the negative signage logic, but in the first pic, youve got 4000 coming in, and 3500 going to grid, with the balance going to 576W of loads. The MPPT is going mostly to battery. Anything being generated by PV charger stays in the house. In the second picture, 84W more is going out to grid, than coming from the big PV array. I presume this 84W is coming from the PV charger. What I'm asking, is whether you can prove that PV charger can put out 500W to grid, by turning loads off. Youve got two options. Either it's a software bug, or the multi doesn't like routing PV charger to grid.
0 Likes 0 ·
blackmarlin avatar image
blackmarlin answered ·

The best I could see was about 200 Watts to the grid. If there would be no load in the house, all the production would be exportet to the grid (this image was taken as I was testing to disconnect the PV inverter).

It is not clear to me why the MPPT is throttled down when the battery is full. Tomorrow I will test if there will be any difference if I set the float voltage = charge voltage. Currently I have 54V float voltage and 55.2V charge voltage.

Best regards

Michael

1678732067410.png


1678732067410.png (118.4 KiB)
1 comment
2 |3000

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

astrayan avatar image astrayan commented ·
Or.... put the absorption down to a high float value, and set the absorption time to 5 hours. It's a good thing you only have a small amount of panels on the Terrasse. You aren't wasting all that much.
0 Likes 0 ·
blackmarlin avatar image
blackmarlin answered ·

I think the problem in my setup was that I had configured the same charge voltage 55,2V as DVCC maximum charge voltage and additionally in VE Configure as absorption voltage.

I changed it now in VE Configure to a higher value (57,6) and left it at 55,2V for DVCC maximum charge voltage. I am not 100% sure but this could have prevented the PV charger to raise the voltage to the automatically configured 0,4V offset which is necessary to export all the 2kW of power in my case.

Now I can see also higher PV power from PV charger Terrasse exported to the grid. But I don't see the float state of the working as expected. The battery is constantly charged / discharged with low current. This was not the case in the setup before.

Best regards

Michael

1679164459367.png


1679164459367.png (29.7 KiB)
1 comment
2 |3000

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

astrayan avatar image astrayan commented ·

https://diysolarforum.com/threads/anything-wrong-with-these-multiplus-settings.16643/


I suggest you read that thread. They discuss lifepo4 and multiplus settings. I still havent figured out what the repeated absorption is.

0 Likes 0 ·
blackmarlin avatar image
blackmarlin answered ·

I think I have to correct my post. The improvment is not related to the offset but to the circumstance that I have reduced the DVCC maximum charge voltage which prevents the Seplos BMS from disabling the discharge switch (MOSFET).

Is there any relation? I thought this could be a way to reach float state (if the discharge MOSFET is opened), but in that case the MPPT is limited.

2 |3000

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

max78 avatar image
max78 answered ·

Can I see the value of the Modbus register 791 (MPPT is ON, running throttled) also in the VRM in the extended diagram section? Or with MQTT?


2 |3000

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

martin-henning avatar image
martin-henning answered ·

Did you have activated the Battery Monitor in den Multiplus configuration? If so, that might be the problem...

2 |3000

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

felix1904 avatar image
felix1904 answered ·

I have a similar problem.. why the battery monitor can be the problem ?

I my system there is no external battery managment or controlling - dvcc is off.

MPPT is charging the battery until it is nearly 100% SOC and then reduces the charging power to 0Watt. I have DC and AC coupled PV.

I just saw in the settings off mppt that the charge mode is "float" and my multiplus says "bulk".. maybe this i a sign that something is wrong.

1701261681391.png



1701261681391.png (57.3 KiB)
1 comment
2 |3000

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

albundy0815 avatar image albundy0815 commented ·
yesterday I had the same behavoir. After rebooting the CerboGX the MPPTs where online again and produce. Also the MP2 feed it the DC PV.

Did you had the same issue again?

0 Likes 0 ·