question

cdev avatar image
cdev asked

How to overrule Max CCL from BMS?

Hi all,
i'm using a MPPT RS 450/200 48V with 8kw peak connected.
I'm using a Lifepo4 Battery (china product) which is connected by CAN to a Venus System.
The Battery - identified as Pylontech - reports a Max CCL 70A - thats why i'm getting a maximum from ~3600W from Panels.
But on the other site a inverter is pulling 600W
So there should be a maximum 4200W possible.
But as BMS is telling only 70A i'm getting only this 70A.

How i can bring the MPPT RS to give more than the 70A on DC site?
Any way to change settings (maybe over root CLI on Venus?)
Or using Node Red?

Btw. Battery Specs say Max Charge and Discharge is 100A - so there should be no risk to do that.

BMSccl
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8 Answers
nickdb avatar image
nickdb answered ·

Loads tend to draw the bus voltage down which should also ramp production.

In a managed system the battery is king, with third party devices, any coordination is lost, but it should still ramp when the DC load (has enable DC system been set) draws the battery down, but until that happens it has no way of knowing there is something else to supply and will only cater for what the battery needs.

You can't nodered around this behaviour.

You might be better off removing the BMS management and rather experimenting with voltage settings in the charger, though that would be better with a shunt installed.

Best solution is a Multiplus.

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Alex Pescaru avatar image Alex Pescaru commented ·

You are saying that if he has "Has DC system" enabled in Venus OS, then the RS can generate more than what BMS is asking and it's published on the CAN bus by the Venus OS in the VE_REG_LINK_CHARGE_CURRENT_LIMIT register?

Thanks

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nickdb avatar image
nickdb answered ·

The CCL does not limit all DC production, that's all it will allow to go directly to the battery.

Sounds like some other setup or installation issue.

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Alex Pescaru avatar image
Alex Pescaru answered ·

Yes, you are right, but if the RS sees on the CAN bus that the Venus tells 70A, it will not generate more than that. It will limit there the current.

The Venus, if the inverter is telling how much needs, should communicate to the RS the sum of consumptions.

Is the inverter also Victron?


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cdev avatar image
cdev answered ·

No, it is not an Victron inverter. At the moment it is a Hoymiles one. Thats why i had the idea to use NodeRed to send 600W to the Venus / ESS and it will put that on top of the 70A
I could also get the Inverter data by MQTT
So from MQTT -> NodeRed -> Venus
But i dont know which Nodes i need to use

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Alex Pescaru avatar image
Alex Pescaru answered ·

@nickdb

Indeed, as you are saying, according to Kirchhoff's first law, the current will be shared between the inverter and the battery. But that will mean that the 70A will be divided between the battery and the inverter. Because the RS will not generate more than 70A, because the BMS, which is king as you say, is telling 70A and that is what Venus is later communicating to RS.

But I have the impression that he wants the full 70A to go to the battery and additionally some to the inverter. Therefore he needs that Venus to tell the RS to generate the sum of those two.

LE:

Now I realize something... You are saying that if he has "Has DC system" enabled in Venus OS, then the RS can generate more than what BMS is asking and it's published on the CAN bus by the Venus OS in the VE_REG_LINK_CHARGE_CURRENT_LIMIT register?

@cdev

But in the same time, that additionally inverter current you want to add, needs to be continuously monitored and communicated to the Venus and later to the RS, because otherwise it could end up in a situation when the RS is generating more than 70A and the additional current could be dangerously absorbed by the battery, if the inverter "doesn't want it"... But if the BMS is wise enough and doesn't absorb more than 70A, the better.

Through NodeRed I don't know how to do it, but you can modify some scripts inside Venus OS in order to accommodate what you need. The functions you need to tackle are in the /opt / victronenergy / dbus-systemcalc-py / delegates / dvcc.py script. Look for "max_charge_current" variable and how it's processed.


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cdev avatar image cdev commented ·

Thanks, i will check that. It should be also not critical if battery gets more than 70A because specs of the battery say it can work with 100A - so i dont know why the limit is 70A (Waiting for feedback from the PowMR about that).
Monitoring / Communication should be no problem, because i get all data from all systems by MQTT - also for building grafana dashboards. So it should be possible to use the mqtt data in a Node Red flow - if it is somehow possible.

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cdev avatar image
cdev answered ·

Hi all,
thanks for your help!
To give some feedback - i was able to change the python scrip on the Victron, so that the 70A is ignored and i set it to 85A.

In parallel i was in contact with the Vendor of the Battery - it was not really helpfull because the (1st lvl?) Support did not understand what they are talking about. Th RS232 Port on my battery is defect, but after some testing i was able to communicate with the BMS with RS485.
So i changed the Limitation on the BMS itself also now. OC Alarm was set to 80A and OCP to 100A

I could not find a Limitation of 70A, but i changed the OC Alarm to 98A. Now i can see that the BMS is telling the Victron System a Max Charge Current of 88A
It seems that the P16S100A BMS is using OC Alarm Current -10A for the Communication to the Inverters. And with max 88A i'm fine and i think that is not Critical for the Battery. (0,44C)


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Fideri avatar image
Fideri answered ·

I don't know about pylons and your batteries. Anything that spoofs pylons or uses pylon BMS doesn't necessarily have the same characteristics. So the charge current can be very different.

How about DVCC and a smartshunt if you have DC loads? According to the manual, DVCC respects the BMS CCL but adds on the amount needed by the loads. It's not clear if this works with non-victron equipment.

F.

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cdev avatar image
cdev answered ·

On the DC site i would need a Inverter which can Communicate with the Venus System - the Hoymiles i use at the moment does not Support that.
I'm happy to have now 88A CCL - that should be enough and if i would go to unlimited, it would be not that often over the 88A - so i'm not loosing that much.

What i could do is using nodered to Set the CCL in DVCC
For example, remove Limitation from BMS or set it to 100A or 120A
Than create a nodered flow which set the Limit in DVCC to lets say 95A and get the DC Load from the Hoymiles by MQTT and than set 95A + x A from.



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Fideri avatar image Fideri commented ·

That makes sense

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Related Resources

Victron VE.Bus BMS product page

Victron 3rd party BMS compatibility page

Additional resources still need to be added for this topic