question

karel avatar image
karel asked

Smart Solar 150/70 MPPT yield limited by Pylontech Bty

Please assist, I have a 48/3000/35 Multiplus II, Venus GX, Pylontech 2000 and 150/70 Smart solar MPPT connected to 4 PV strings. I noticed over a long period that with 3 strings connected and also now with 4 strings connected to the MPPT that at around 10h00 every sunny day my MPPT solar yield drops with about 400W on a 3 string input but 900W on the 4 string input. After long investigation of trends I found that it seems at some point during Bulk charging at which stage the Bty shows 100% for a long time already, the MPPT Pylontech bty voltage graph raises slightly from about 52.26V to 52.3V and then suddenly the MPPT current output drops significantly without any change in the sun exposure. I make use of ESS feed in excess power as well as DVCC with no current limits set or time dependent constraints in any configuration.

I was told that my Pylontech Bty (1 only, proposed 2) is the problem and that the firmware on the Multiplus II version 459 does not handle the excess PV power available very well. As such as the pylontech dictates the MPPT charging algorithm, it throttles the MPPT and also the feed in power to the grid. The proposal is to upgrade the Multiplus II firmware to version 475 which may help. Does anyone know what the reason or solution could be, would not like to buy another pulontech to solve this problem. Attached 2 graphs to indicate the scenario


MPPT Controllers
solar-1.jpg (70.7 KiB)
solar-2.jpg (67.0 KiB)
2 comments
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 ·

@Karel

The newer firmware should be loaded on all the devices including the venus in the system for the feedback to work well. This is good practice when a new system is commissioned.

0 Likes 0 ·
Show more comments
4 Answers
dgnevans avatar image
dgnevans answered ·

Is your Mutliplus II back feeding ie grid tied or just supplying your load requirements. Are your Pylontech at 100% SOC at 10 am. depending on how your system has been configured. The BMS on the battery could have a charge limit which would limit your charge current.

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.

karel avatar image
karel answered ·

Hi, the Multiplus is back feeding into the grid, usually about 2000W but have the potential to rise to 3000W. All the tests I have done have indicated that the problem is triggered when the Pylontech battery reaches a voltage of 52.1V. Below 52.1V the MPPT runs maximum feedback to the grid, Above 52.1V the MMPT current drops about 25% . Switched the BMS monitor from Pylontech to Multiplus II and exactly the same happens.

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.

karel avatar image
karel answered ·

Multiplus II is back feeding into the grid and not just supplying my load requirements. The pylontech is usually at 100% SOC. I can understand the BMS limiting the charge limit but something (pylontech, multiplus or MPPT) is limiting the back feeding into the grid at what seems to be the point where the MPPT charge voltage increases for some reason. I have done more testing where I disconnected the can-bus on the pylontech to remove the pylontech as a system charge controller and changed the BMS to the VE-bus i.e I assume the multiplus becomes the controller and I still have the same problem.

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.

puntasso avatar image
puntasso answered ·

Hello! Did you resolve the issue? I have the same problem, the system is limiting the max PV power when battery charged and feeding to grid.

4 comments
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.

nickdb avatar image nickdb ♦♦ commented ·

There are no issues with pylon batteries and victron, if they are configured correctly.

some times issues may be seen on new installs while they balance.

Step through the attached guide, checking your config and settings and making sure firmware is current.

If it is all compliant, it just works.

https://www.victronenergy.com/live/battery_compatibility:pylontech_phantom

0 Likes 0 ·
puntasso avatar image puntasso nickdb ♦♦ commented ·

Yes, there is an issue with Pylon and Victron:

- Multiplus II 48V 5000VA 70/50

- 2 x US3000C Pylontech.

- Cerbo GX.

- 5.2kW PV in DC-coupled.


When batt at 100% SOC, not all the PV power is feeded to grid. It only feeds grid at 74Ah in DC, that is the DCL. In @Karel question you can see that Multiplus cuts feed-in grid power at 50A (DCL for US2000).

So the issue with Pylon and Victron is clear: MS has a "hidden" limit to feed-in grid in DC-coupled when batt is full and all power comes from PV. That limit is DCL parameter, and this is NOT a good performance.

0 Likes 0 ·
nickdb avatar image nickdb ♦♦ puntasso commented ·
You don’t seem to understand how the system works, you also have too little battery for that inverter.

There are 10’s of thousands of working sites, so the issue is your setup.

Rather get a professional to help you instead of blaming the product.

0 Likes 0 ·
puntasso avatar image puntasso nickdb ♦♦ commented ·

Hey guy. First at all, respect. This is a forum where we ask our questions about Victron products. Here no one is blaming any product. It's obvious that probably I have an incorrect setup, and that is the reason I ask in this forum, to get help from people who knows better the products.


If you don't know what is the purpose of a forum, learn first or get professional help. Education have an issue in your setup.

Regards.

0 Likes 0 ·