Victron MultiPlus-II 48/3000 low voltage cut-out with LiTime ComFlex 48V

[dcg9381]

Hi, I've got a Victron Multiplus-II 48/3000. It's connected to Cerbo. I have comms setup (and functional) to 2 x LiTime 48V (51v) 100aH ComFlex batteries.

If I understand right, I'm using DVCC which leverages the battery comms and BMS to control charging, battery cut off, recovery etc. This is what LiTime's manual says about those voltages:


The Victron is shutting down inverting. Can I assume in DVCC mode that the actual "low battery" signal is triggered from battery coms?

"Managed CAN-bus batteries: In systems with a managed CAN-bus BMS battery connected, the GX device receives a Charge Voltage Limit (CVL), Charge Current Limit (CCL) and Discharge Current Limit (DCL) from that battery and relays that to the connected inverter/chargers, solar chargers and Orion XS. These then disable their internal charging algorithms and simply do what they're told by the battery."








Interestingly enough, indicated battery capacity is 68%. I've got almost no load on this system (been running it for days with just some LED lights):





Thoughts? I've reached out to LiTime support.

 

[sunshine_eggo]

Hi, I've got a Victron Multiplus-II 48/3000. It's connected to Cerbo. I have comms setup (and functional) to 2 x LiTime 48V (51v) 100aH ComFlex batteries.

If I understand right, I'm using DVCC which leverages the battery comms and BMS to control charging, battery cut off, recovery etc. This is what LiTime's manual says about those voltages:
View attachment 258965

The Victron is shutting down inverting. Can I assume in DVCC mode that the actual "low battery" signal is triggered from battery coms?

"Managed CAN-bus batteries: In systems with a managed CAN-bus BMS battery connected, the GX device receives a Charge Voltage Limit (CVL), Charge Current Limit (CCL) and Discharge Current Limit (DCL) from that battery and relays that to the connected inverter/chargers, solar chargers and Orion XS. These then disable their internal charging algorithms and simply do what they're told by the battery."

View attachment 258970

View attachment 258967

View attachment 258968


Interestingly enough, indicated battery capacity is 68%. I've got almost no load on this system (been running it for days with just some LED lights):


View attachment 258969


Thoughts? I've reached out to LiTime support.

A 16S (51.2V) battery at 47.4V is at near 0% SoC.

The 68% is bogus.

BMS require at least one full charge to the trigger voltage to establish 100%, and possibly a few cycles to improve accuracy.

BMS is likely shutting down the inverter due to a single cell hitting min voltage.

 

[740GLE]

IMO you need a smart shunt that will track SOC better than the battery BMS.

Yet again another closed loop communication issue.

 

[dcg9381]

BMS require at least one full charge to the trigger voltage to establish 100%, and possibly a few cycles to improve accuracy.

BMS is likely shutting down the inverter due to a single cell hitting min voltage.

Thanks. Super helpful.

IMO you need a smart shunt that will track SOC better than the battery BMS.

I could add a Victron shunt, but assuming displayed voltage is accurate, should I just override BMS control and enter battery parameters manually?

Yet again another closed loop communication issue.

Yea, seems like it if this is displaying 60% SOC at 47V.

 

[740GLE]

Can you look at any of the parameters of the LiTime BMS?

Can you change any of the settings?

 

[sunshine_eggo]

I could add a Victron shunt, but assuming displayed voltage is accurate, should I just override BMS control and enter battery parameters manually?

I would hold off on adding another shunt until you've demonstrated the battery SoC is consistently unreliable vs. what is expected in a new install. SoC of as-received batteries is always junk. The BMS has to be "calibrated" with a full charge.

I would fully charge the batteries to at least 56.8V before I made any hardware or configuration changes.

 

[Suijkerbuijk]

It can be that if the inverter go in load a big dip come and shutdown . (Yes if you set eco mode on it have dips a lot by Drain the capacitor that are beult in .)

A shunt will not help if your bms shutdown
So long that is not fix first .

 

[740GLE]

It can be that if the inverter go in load a big dip come and shutdown . (Yes if you set eco mode on it have dips a lot by Drain the capacitor that are beult in .)

A shunt will not help if your bms shutdown
So long that is not fix first .

Except BMS is showing 47v that’s 2.9v which is pretty much zero SOC.

I’d agree any sort of load will bring down the battery under 46v.

 

[Suijkerbuijk]

Except BMS is showing 47v that’s 2.9v which is pretty much zero SOC.

I’d agree any sort of load will bring down the battery under 46v.

Its 47.4= 2.9625 volts on a cell .
But i do not see all cells .
So it can be that on cell is low and other are high .
So the bms calculation that ah on all cells

So it can be that one cell is 2.550 volt and the rest is 2.99 volts.
This bms calculation is off on that moment .
That is the reason the bms bullshit calculation never gone works

Funny thing see my file just for the fun .
Both are parallel connect.
All cell volts are almost the same.
But the Ah is not the same.
Its way off with 15% +/-

 

[dcg9381]

Can you look at any of the parameters of the LiTime BMS?
Can you change any of the settings?

I haven't found cell voltages, but I have it operating in a linked mode.
No setting changes other than setting the com to Victron.

I think you guys were right, the SOC is not properly initialized. I started charging it and it quickly went up to about 95% SOC and it's been holding there for a few hours, so something isn't calculating right. Will see if a full charge (I haven't every fully charged these) fixes it.

 

[Suijkerbuijk]

I haven't found cell voltages, but I have it operating in a linked mode.
No setting changes other than setting the com to Victron.

I think you guys were right, the SOC is not properly initialized. I started charging it and it quickly went up to about 95% SOC and it's been holding there for a few hours, so something isn't calculating right. Will see if a full charge (I haven't every fully charged these) fixes it.

Full charge is all cells have to be 3.65volts.
A soc reset is on 3.55volts

The other thing is this.
You have to see if the bms soc vs volts how its program by the company.
I see in my own case that 40 and 50% have the same volts on the soc so it stay longer tell you that its 40% .
Its stupid .
Than again the bms soc vs % its soc is so small.
That the reason its done.

 

[sunshine_eggo]

Full charge is all cells have to be 3.65volts.

Nope.

LFP can be charged to 100% at anything at or above 3.40V. 3.40V requires a very long absorption period and a near zero tail current. 3.65V requires a few minutes of absorption time and a tail current of .05C.

Absorption time is also dependent on initial C rate. Low rates require less absorption time.

A soc reset is on 3.55volts

This depends on the BMS and some can be adjusted.

I haven't found cell voltages, but I have it operating in a linked mode.
No setting changes other than setting the com to Victron.

You might be able to get some cell data by going into the device list on your cerbo. I think the details and parameters options may get you cell data.

I think you guys were right, the SOC is not properly initialized. I started charging it and it quickly went up to about 95% SOC and it's been holding there for a few hours, so something isn't calculating right. Will see if a full charge (I haven't every fully charged these) fixes it.

It's making SoC guesses based on voltages. Once it gets a valid sync, it should start accurately counting current and reporting SoC.

Since you've never fully charged it, you may find that you can't get fully charged due to cell imbalance.

 

[Suijkerbuijk]

Nope.

LFP can be charged to 100% at anything at or above 3.40V. 3.40V requires a very long absorption period and a near zero tail current. 3.65V requires a few minutes of absorption time and a tail current of .05C.

Absorption time is also dependent on initial C rate. Low rates require less absorption time.



This depends on the BMS and some can be adjusted.



You might be able to get some cell data by going into the device list on your cerbo. I think the details and parameters options may get you cell data.



It's making SoC guesses based on voltages. Once it gets a valid sync, it should start accurately counting current and reporting SoC.

Since you've never fully charged it, you may find that you can't get fully charged due to cell imbalance.

On my bms it tell that a cell 100% cap is on 3450mv
Its the basic load setup from jbd .
Cell full volts is 3500mv .

 

[sunshine_eggo]

On my bms it tell that a cell 100% cap is on 3450mv
Its the basic load setup from jbd .
Cell full volts is 3500mv .

So you're saying that your statements aren't even true for you?

And you can change them.

 

[Suijkerbuijk]

So you're saying that your statements aren't even true for you?

And you can change them.

Nope i have change them.
Its compleet stupid how the company had set them

Same with balance cell option.
3400mv .
I have set it back to 3370mv.
And now my cells stay nice balance.
It kick in faster so that a slower cell have time to pull up.
After long make my self Crazy day that i had 2 cells out of balance and i can not open the battery.
I have play with it till i find the sweet spot.


Lifepo4 battery are just like a women.
You need to fine that spot or you are always wrong.

 

[sunshine_eggo]

Lifepo4 battery are just like a women.
You need to fine that spot or you are always wrong.

Nah.. you just need to know how to massage them!

 

[Suijkerbuijk]

Nah.. you just need to know how to massage them!

Lol.
No i stay singel
This way i'm always correct

 

[sunshine_eggo]

Lol.
No i stay singel
This way i'm always correct

wisdom. I'm on wife #2, but it's been 25 years, so I get to be correct sometimes.

 

[dcg9381]

Since you've never fully charged it, you may find that you can't get fully charged due to cell imbalance.

Isn't this the point of buying a battery with an internal BMS?

Do I'll "load test" this thing. Is there an easy way to get discharge kWh out of Cerbo / Victron reporting?

 

[740GLE]

I haven't found cell voltages, but I have it operating in a linked mode.
No setting changes other than setting the com to Victron.

I think you guys were right, the SOC is not properly initialized. I started charging it and it quickly went up to about 95% SOC and it's been holding there for a few hours, so something isn't calculating right. Will see if a full charge (I haven't every fully charged these) fixes it.

What’s the current going into the battery?

What’s the charge parameters?

How are you charging the battery? The multiplus? A victron SCC?

Do you have the multiplus voltage sensor connected to the battery terminal?

 

[dcg9381]

What’s the current going into the battery?

It's limited to 50A in Cerbo, but I believe the multiplus-II is limited to 30A at 48V. I have not been actively charging it.. It was never charged to 100%. (doing that now)

What’s the charge parameters?

VE.CAN communications. Victron uses parameters from the battery set. Protocol is Victron.

How are you charging the battery? The multiplus? A victron SCC?

Multiplus-II 3000/48.

Do you have the multiplus voltage sensor connected to the battery terminal?

No. Battery and Cerbo are reading the same voltage though.

 

[740GLE]

Ahh I forget closed loop shares than information.

It’ll be interesting to see how much it takes to get to 100%.

 

[dcg9381]

It’ll be interesting to see how much it takes to get to 100%.

I'm interested too. What's the easiest way to get Victron to give up charge/discharge data?

I have the dashboard up:

VRM Portal - Victron Energy

VRM by Victron Energy gives realtime insights into your energy. Monitor complete energy systems, tanks and temperatures remotely.

vrm.victronenergy.com

 

[sunshine_eggo]

Isn't this the point of buying a battery with an internal BMS?

No. In the normal operating range, the cell voltages are too close even when they are imbalanced. Charging to the manufacturer's prescribed charge voltage is required to ensure the BMS is given the opportunity to balance. If you've habitually not charged to the manufacturer's recommended charge voltage, you've crippled the BMS's ability to balance.

Do I'll "load test" this thing. Is there an easy way to get discharge kWh out of Cerbo / Victron reporting?

You should be able to plot an appropriate widget on the VRM advanced tab.

I'm interested too. What's the easiest way to get Victron to give up charge/discharge data?

I have the dashboard up:

VRM Portal - Victron Energy

VRM by Victron Energy gives realtime insights into your energy. Monitor complete energy systems, tanks and temperatures remotely.

vrm.victronenergy.com

What other widgets do you have available for the Battery Monitor [512]?

 

[dcg9381]

No. In the normal operating range, the cell voltages are too close even when they are imbalanced. Charging to the manufacturer's prescribed charge voltage is required to ensure the BMS is given the opportunity to balance. If you've habitually not charged to the manufacturer's recommended charge voltage, you've crippled the BMS's ability to balance.

Got it.

You should be able to plot an appropriate widget on the VRM advanced tab.