Charge current at high SOC not limited

[R0Li84]

I'm running a 16s 280Ah LifePo4 battery with JKBMS connected to a Victron Mulitplus II.
SerialBattery is installed with version 0.142 and everything works pretty good so far.

My only problem is that charging current does not limit when I'm at high SOC.
In utils.py I have added charge current limits as follows:

`######### SOC limitation #########
# Description:
# Maximal charge / discharge current will be increased / decreased depending on                                                                                                                                                                                                                                             >
# The State of Charge (SoC) charge / discharge current will be in-/decreased de                                                                                                                                                                                                                                             >
# Example: 16cells * 3.45V/cell = 55,2V max charge voltage. 16*2.9V = 46,4V min                                                                                                                                                                                                                                             >
# Cell min/max voltages - used with the cell count to get the min/max battery v                                                                                                                                                                                                                                             >
MIN_CELL_VOLTAGE = 2.9
MAX_CELL_VOLTAGE = 3.40
FLOAT_CELL_VOLTAGE = 3.35
MAX_VOLTAGE_TIME_SEC = 15*60
SOC_LEVEL_TO_RESET_VOLTAGE_LIMIT = 90

# battery Current limits
MAX_BATTERY_CHARGE_CURRENT = 100.0
MAX_BATTERY_DISCHARGE_CURRENT = 100.0

# Charge current control management enable (True/False).
CCCM_SOC_ENABLE = True
# Discharge current control management enable (True/False).
DCCM_SOC_ENABLE = True

#charge current soc limits
CC_SOC_LIMIT1 = 98
CC_SOC_LIMIT2 = 95
CC_SOC_LIMIT3 = 91

#charge current limits
CC_CURRENT_LIMIT1 = 5
CC_CURRENT_LIMIT2 = MAX_BATTERY_CHARGE_CURRENT/10
CC_CURRENT_LIMIT3 = MAX_BATTERY_CHARGE_CURRENT/5

#discharge current soc limits
DC_SOC_LIMIT1 = 10
DC_SOC_LIMIT2 = 20
DC_SOC_LIMIT3 = 30

#discharge current limits
DC_CURRENT_LIMIT1 = 5
DC_CURRENT_LIMIT2 = MAX_BATTERY_DISCHARGE_CURRENT/4
DC_CURRENT_LIMIT3 = MAX_BATTERY_DISCHARGE_CURRENT/2

# Charge voltage control management enable (True/False).
CVCM_ENABLE = True

# Simulate Midpoint graph (True/False).
MIDPOINT_ENABLE = False

#soc low levels
SOC_LOW_WARNING = 20
SOC_LOW_ALARM = 10`

Under parameters I see that the charge current is limited at high SOC e.g. to 5A like I have specified. However, it seems like charge current is not limited because I have seen very high charing speeds at high SOC. E.g. ~30A @ 98% SOC.

Can somebody have a look on my code above? I really struggle here and cannot find the mistake. Would be nice to solve this, as I think it could negatively influence my battery lifetime.

[Louisvdw]

If you see the smaller values under the parameters section, then the driver is working.
Make sure you do have DVCC enabled, and also check that you do have the serialbattery selected as the Battery Monitor in your GX.

You might still see larger currents flowing even if everything is set correctly, but this should be just for small amounts of time. The battery is used by the ESS system to buffer any sudden changes is power usage that is required by your system. So if you have a large load suddenly stoppings, the ESS system ramps down the MPPT chargers over a second or two and during that time the excess power has to go somewhere (which is to the battery)

[LarsAndersenDenmark]

Hi Louis

If I have 2pcs MPPT 250/100 (for a 7.5kWp PV), a full battery and only 1 MP2 48v/5000, then I might have a too small MP2 to take the load from the 2 MPPT's. Then they should be told to lower the power and not just charge the battery even further. Is this taken care of you think? I still have too little sunny days to do some real tests, but you might already have some good inputs for this.
Update: The MPPTs do not respect the CCL, only the CVL is respected according to my tests.

BR,
Lars

[exenbema]

i have now changed to voltage based and disabled the SOC management completly (1h ago:))
because my daly does goodm but count SOC really bad - i cant change the 2AMP setting...

i m soo excited that you programmed so that this is now an option, i m so happy - because with SOC based i had readjust weekly my daly per PC BMS programm to lower the soc

[R0Li84]

@Louisvdw - first thanks also for your great work.

I had to wait for sunshine (winter here in Germany) to test everything again (I've done a fresh installation to make sure everything ist set up correctly). But unfortunately it did not limit the charging speed at high SOC today. DVCC was enabled but Battery Monitor was set to "Automatic" (I missed this today).

I will check again in a few days (weather forecast is not good for solar power at the moment) if it works after I have set Battery Monitor to SerialBattery and give an update here.

[R0Li84]

@Louisvdw - sorry for my delayed response but I had to wait for sunshine here in cold + clouded Germany.
Today I had the change for further testing. I have taken a video showing the issues I'm confronted with. As you can see, the parameters from serialbattery are correctly taken over, but the functionality to limit the charging current is not there.

Would be nice if you could help me to fix this issue.

Video Link (sorry for my "bavarian english"):
https://vimeo.com/789689709

[Louisvdw]

You have to choose the one that you want to be the monitor and thus limit the charging. (so normally the smallest size)

[ghost]

Maybe your problem is related to this discussion?
https://community.victronenergy.com/questions/167579/ladestrombegrenzung-wird-ignorriert-bei-dc-einspei.html
Is DC Feed-In activated?

[R0Li84]

You have to choose the one that you want to be the monitor and thus limit the charging. (so normally the smallest size)

Hey, that is a good hint. DC Feed-In is activated. I get some money for the electricity I supply to the grid, so it would be stupid to turn it off. As I understood, this shuts off all external limits? In that case it seems that I must go with a smart shunt (I have it anyhow here and plan to install it as I would like to add a second battery with own BMS).

[ghost]

@Louisvdw can you confirm that the Charge limits are deactivated when DC feed in is activated?
@R0Li84 Using more Batteries without a Shunt, this could also be a soulution if you want to give it a try: https://github.com/arrow1800/Victron-VirtualBattery

[R0Li84]

@locke981 - DC Feed-In is really the thing stopping mainly all parameters / settings coming from serial-battery (utils.py).
I'm still waiting for sunshine, but with DC feed disabled I noticed yesterday that my DC connected MPPT trackers did not work (utils.py is disabling charging at low temperatures). After I turned DC-Feed on everything started to work, ignoring utils.py!

@Louisvdw - can you check and confirm? If this is right, it would be really good if you could highlight this in the Wiki! Local rules might be different, but at least in Europe normally everybody is feeding to the grid if the batteries are full (because we get a little compensation for it).

[stefan1967]

Are there any news regarding the DC feed problem? I have the same issue, if DC feed is on, all parameters from utils.py are ignored. Think its a victron problem, but with DC feed on the serial driver is unfortunately more or less useless.

Thanls for any information.

[R0Li84]

Well, like I explained it to myself, the Smart Shunt is sitting in the power line going to the battery. It can measure exactly what is going in / out + SOC of battery. By having it sitting in the supply line, it can furthermore control the power to the battery / reduce it. This is not possible with serial battery, which is just a software that can only control already existing hardware (MPPT).

[smurfix]

Sorry but why exactly do you think serialbattery can't do any of that? It talks to a BMS, which should know which max voltage+current the battery can tolerate. it relays that information to the Venus system via DBus, which then forwards that to the MPPT(s) and the inverter(s).

[stefan1967]

HI Smurfix, yes that all works fine as long as you do not siwtch on the DC feed in to Grid option. If you switch on this feature, the driver is not working - all parameters from utils.py are ignored. Thats not a fault of the driver, its a probelm (or Victron says feature ;-) of Victron.
With DC feed in on, the MPPTs are always run at full power and you are not able to regulate the amperes which are going from the MPPTs to your battery.
You can do it with node red using the set grid value.

[LarsAndersenDenmark]

Sorry but why exactly do you think serialbattery can't do any of that? It talks to a BMS, which should know which max voltage+current the battery can tolerate. it relays that information to the Venus system via DBus, which then forwards that to the MPPT(s) and the inverter(s).

The issue is for ie jk bms, that SOC is not working and for Victron, the feedin excess gives full throttle signal to mppts and forward all current to the battery without respect to the max current set in the serialdriver. The Victron system could choose to control currents going to battery acc to max amp in serialdriver and then feedin all above that.... but it doesn't.
Also if you have too little inverter power from ie MP2 to feedin excess, the mppt's will just go full throttle and exceed battery voltage limit and the system will go into overvoltage, which again leads to mppts switch on/off giving voltage fluctuations. This do not happen with feedin excess in off.

[LarsAndersenDenmark]

HI Smurfix, yes that all works fine as long as you do not siwtch on the DC feed in to Grid option. If you switch on this feature, the driver is not working - all parameters from utils.py are ignored. Thats not a fault of the driver, its a probelm (or Victron says feature ;-) of Victron.

With DC feed in on, the MPPTs are always run at full power and you are not able to regulate the amperes which are going from the MPPTs to your battery.

You can do it with node red using the set grid value.

I think its only the CCL that is ignored, but that is also quite serious. Especially for me who has two mppts for my 7,5kWp array and only one MP2 48/5000, which is also derated in grid code. Grid code derating is also not correct, but thats another story :-)

[hoschult]

I had also a problem that CCL was not respected when DC feed is on. See my issue #445
No it worked out (in short: reducing float cell voltage).

[exenbema]

@LarsAndersenDenmark - I'm currently running with JKBMS only, as I'm planning to install a second battery back. My plan is to use serial battery to monitor e.g. cell voltages (that works pretty nice). But charging control shall be done with the Smart Shunt. I personally also think that this is more safe, as I do not fully trust a Chinese BMS system (if this fails, you lost control over your battery).
Currently I have reduced MAX_CELL_VOLTAGE to 3.42V. This limits the charging voltage to 54,72V and also reduces automatically the charging speed at high SOC (I can only charge very very slowly to 100% - but that is ok for now). All other settings like charge current soc limits will be ignored when you turn DC Feed on. SOC limitation works.

Sound like the way I personally also think is the right way.

1. Do you know if there is a more explaining guide for i.e. choosing false/true for the settings in the JKBMS driver?
2. Any places where it is explained which settings are ignored and which are not, when feed-in is active? You say charge current limits for SOC are ignored, but also that "SOC limits works". I have changed setting for both individual cells and for SOC, but I cannot conclude which settings do actaully control my system and which are ignored due to feed-on active. Would be nice with some more explanation :-)

Due to above, I have also lowered my voltage setting to ensure batteries are not charged to high above the actual max. voltage when in-feed active. I had set my max voltage to 4,1/cell which is 57.4volts, but the system actually did switch kinda-off battery charging at that voltage level. But due to I actually do have a high charge current near top SOC, the system did overcharge my batteries bit-by-bit due to the high PV currents flowing when feeding to grid also.

Hopefully it is understandable :-)

But charging control shall be done with the Smart Shunt. -- how you set this ? because i think the limitation the system takes from the driver automatically? to set the battery monitor to shunt its a possibiliy but i think its only how is displayed in the grafic?

[stefan1967]

In my installation all parameters from utils.py are still ignored if DC-feed is on. But be carefull, they are ignored for the current comes from the solar DC loaders only! I have also AC inverters running and for this power comming through the Multiplus, the settings in utils are not ignored.
So for example if I have a max current of 70a in utils.py, and I get 80 amps from the dc-solar loaders this max limit is ignored and only the BMS setting in the JK is the limiter.

But if i get 70 amps from the solar loaders and additional 20 amps from the multiplus (from the AC inverters in front of the multiplus) the utils.py is not ignored but only for the power coming from the multiplus - in my szenario, 70 coming from DC loaders, 10 coming from the multiplus, 10 are going to the grid....

[LarsAndersenDenmark]

It make sense that current limitting from DC solar is ignored, else they cant feed into grid. But still no current should flow to the battery. The MP2 should ramp up and deliver excess current to grid. Of course running with feed-in active also requires that you do not charge battery to 100% since the battery is a kind of buffer, since it seems like the DC solar chargers are faster reacting than the MP2.

I just cant figure out if my system use the max voltage from the SOC limitiation section in the code or it actually read and react based on individual cells settings in the code....or both (what ever comes first). But if we are sure that only current limits for the DC solar mppts are ignored at feedin active, I'm a bit longer with my testing.
There are still days between we have such days with enough sun, that feed in is actually done, which affect my testing planning :-)

[LarsAndersenDenmark]

I have also reduced float cell voltage. However, this limits the charging speed too early for my understanding, and you need a lot of time to fine-tune your system. If you like it - go with it.

For me, a Smart Shunt for the control with DC-feed-in is the best solution.

Hi @R0Li84
Just to be 100% sure. The Victron Smart shunt WILL reduce and also stop the MPPT charge to the battery if battery is full? Will this be done even if my single Multiplus2 cant invert alle the power from the 2pcs MPPT 250V/100A?
What settings cna be set to control the MPPT's if Smart shunt is inserted? CVL(max voltage of battery), CCL(a max current to slower charge battery and feedin rest), SOC?
Thank you very much in advance.

[exenbema]

the question is how controls the mppt and so on. in my experience its not dvcc or other settings, its always the bms. so bms (the driver then) controls everything...but i m not complete sure about that. so the question is how can the smart shunt control mppt (and so) if the bms sis doing that

[stefan1967]

Hello Holger and this also works with DC Battery load from the PV DC Charge Controllers? Regards stefan. Von meinem/meiner Galaxy gesendet

…

-------- Ursprüngliche Nachricht -------- Von: Holger Schultheiß ***@***.***> Datum: 09.02.23 21:00 (GMT+01:00) An: Louisvdw/dbus-serialbattery ***@***.***> Cc: stefan1967 ***@***.***>, Comment ***@***.***> Betreff: Re: [Louisvdw/dbus-serialbattery] Charge current at high SOC not limited (Discussion #382) I had also a problem that CCL was not respected when DC feed is on. See my issue #445<#445> No it worked out (in short: reducing float cell voltage). — Reply to this email directly, view it on GitHub<#382 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/ALRENLVYA6SIKND4F64PYLDWWVEHFANCNFSM6AAAAAATOGAK3I>. You are receiving this because you commented.Message ID: ***@***.***>

[hoschult]

don't know if I get your question correctly... You mean a "charge scenario" (instead of my case "discharge scenario")?

[stanhausc]

I don't see the set value (utils.py) in the interface, why don't I see it?

IN_CELL_VOLTAGE = 50.0
MAX_CELL_VOLTAGE = 52.0
FLOAT_CELL_VOLTAGE = 51.0
MAX_VOLTAGE_TIME_SEC = 15*60
SOC_LEVEL_TO_RESET_VOLTAGE_LIMIT = 90

# battery Current limits
MAX_BATTERY_CHARGE_CURRENT = 50.0
MAX_BATTERY_DISCHARGE_CURRENT = 60.0

[mr-manuel]

Did you check the FAQ?