I have a new Victron installation that has worked fine for the past few days. Yesterday and today I have been receiving High Cell Voltage warnings. I hoping to get some assistance as to what I need to reconfigure or where to look to resolve this issue. This is a list of my equipment:
six 36v 400w Solar panels configured 3 parallel 2 series for 108v to the Victron MPPT 150/100 charge controller
two EG4 LL 24v 200 Ah lithium ion batteries connected in parallel with a data cable connected to the Cerbo GX.
The negative terminal of the battery bank is connected to a Victron SmartShunt 500A/50mV IP6
The positive terminal of the battery bank and load output of the shunt are connected to a Victron LYNX Distributor M10 bus bar.
Also connected to the bus bar Is a Victron MPPT 150/100 charge controller, Victron MULTIPLUSII 24/3000/70-50 2x120V (UL458) 24VDC dual leg AC inverter
The inverter connects to a 120v AC Breaker panel in our off grid cabin.
The SmartShunt, charge controller and inverter are also connected to a Victron Cerbo GX
The system is programmed as follows:
Victron SmartShunt 500A / 50mV
Battery Capacity: 400 Ah (2x 200Ah batteries in parallel)
Charged Voltage: 28.0
Tail Current: 2.0 %
Charged Detection Time: 3 m
Peukert Exponent: 1.05 (Standard for Lithium Ferrous Phosphate)
Charge Efficiency Factor: 99 %
Current Threshold: 0.10 A
Time-to-go Averaging Period: 3 m
Victron MPPT 150/100 Charge Controller
Battery Voltage: 24V
Max Charge Current: 100 A
Charge Profile: User Defined
Absorption Voltage: 28.1 V (Per manufacturer spec for EG4 24V LL)
Float Voltage: 27.0 V (Per manufacturer spec for EG4 24V LL)
I’m missing info regarding the BMS!? usually a high cell voltage warning comes from the BMS. usually it means that at least on cell has a high voltage due to unbalance.
usually you resolve the issue by balancing the cells.
ps. I just realized EG4 LL has a built-in BMS. Unfortunately it seems to have only 120mA passive balancer. so balancing may take a longer while…
On the Cerbo there is a menu: Settings>System Setup > Charge Control.
Enable limit managed Battery Charge voltage and reduce this in 0.5V steps until the warning goes away. Then start increasing it slowly. (0.1V steps.)
hm, what would be the intention to do so? just to get rid of the warning? I’d prefere to resolve the cause of the warning.
28V (currently set) means 3,5V per cell in average - this is not too much, in case you intend a ~100% charge. Have a look at the LiFePo characteristics:
The ‘orange’ cell was very close to 100% while the others were a little less. So the orange raised to even over voltage error level (and the BMS opened the charge FET) while the/some other cells were just below 3.5V. So the solution was to allow the lower cells to charge and due to that gain voltage. In the end (the next day) all cells were close to 3.5V and there was no cell over voltage issue anymore.
My JK BMS has a “2A” active balancer, and even with that it took some hours to balance. With the 120mA passive blancer of the EG4 LL it will take accordingly longer, and the passive balancer can only ‘tear down the highest cell’, not able to move the charge to the lowers. But it will work.
Anyway to avoid cell overvoltage error, it might be necessary to decrease charge voltage temporarily like @MikeD said.
well, as long as there is only a warning, it’s not necessary to decrease the charge voltage. Only in case it runs into cell over voltage error it is necessary to lower the charge voltage. but ok, to be on the ‘safe side’, you may do anyway…
also important might be to change the charge algorythm. to do balancing, it is necessary to keep the high charge voltage. The currenty set Absorption Duration: 1 hour might be too less…
The charger settings are ignored in an ess with a managed battery.
The alarm exists because the bms has raised it due to a high cell. Slightly lowering the cvl manually allows for the battery to balance just beneath the threshold after which it can be removed. The setting was designed precisely for this scenario and Pylontech specificallly.
The intention is to limit the charging voltage to allow the cells to balance. Once balance is achieved, then the voltage can be slowly increased. This is useful for battery systems where the balancing current is small - they were designed for data-center use, where the charge is usually 24/7. in Solar use, the charge is ~4 hrs per day, and balancing currents should be designed proportionally higher.
Thanks, guys! As I’m new to this, although relatively technically savvy, some of this is going over my head. While I was onsite yesterday when I originally posted, I am no longer onsite but able to access VRM and the remote console so I’m limited to what I can change remotely. I am not able to be back onsite for 3 weeks.
Yes, there does appear to be an imbalance between the cells. Remote Console is showing Lowest Cell Voltage at 3.410V and Highest Cell Voltage at 3.621V. This is a brand new installation and I’ve been told that this is not unusual and will take some time for the cells to balance.
Based on some other support I received, I’ve made a couple of changes. While still onsite, I lowered the Absorption Voltage to 27.6V and Absorption Time to 2 hours. I lowered the Float Voltage to 26.8V.
It seemed to stop the warnings while I was there but I just received a couple of new warnings an hour ago. I went into the Remote Console and made a couple more changes. In the DVCC settings, I’ve enabled Limit Charge Current and set it at Maximum 15A. I’ve enabled Limit Managed Battery Charge Voltage and set the Maximum Charge Voltage to 27.6V. I haven’t yet received any new warnings. Not sure what else I can do remotely but am obviously open to suggestions.
So those changes didn’t solve the issue. I just received a couple more warnings. The warnings seem to clear within 8 seconds to 6 minutes. VRM has suspended my alarm notifications for 24 hours due to high volume so I am actively monitoring it on VRM as I sit at my desk at work.
as I said - as long as it is only a warning it’s not a big problem. anyway you may further lower the Maximum Charge Voltage in DVCC to get rid of the warning. but make sure to increase it on time, otherwise balancing might not happen properly. Watch the cell voltages.
as Nick said - the charger settings are ignored when BMS controlled. DVCC Max is the right setting to limit the charge voltage.
Thanks so much for the advice you’ve offered. Yes, I noticed after changing the Absorption Voltage and Time and the Float Voltage that they remained at their previous settings when I looked in VictronConnect. So, since they are just warnings, are you suggesting that I can keep my existing settings, ignore the warnings for the time being and watch the cell voltages to wait for them to self balance?
let’s be clear and not rely on guessing or maybes.
The warning is generated because a cell has gone (is going) high and the bms is having to do something about this by changing charge parameters. Sometimes taking a module offline.
It will need time on charge to balance and the warnings may persist for some time depending how long it can remain on charge and how good the battery is at balancing. Deep discharges and then longer charging on mains can speed up the process. I am in the process of doing this with another brand and we’re weeks into the process now.
Where this is a lingering issue, it is better for your battery not to have cells sitting in this zone, so manually adjusting using DVCC can keep cells just under that threshold AND allow it to balance without all the alarms and having to keep setting CCL to zero.
It is your battery and what you do about it is your business. Remember this is a site of enthusiasts and accuracy will vary, so you need to be responsible when following advice.
As I have already explained, this is the very purpose of this option in the GX. It was implemented for no other reason.
I guess this was on the MPPT only? Since in the first post you mentioned that the MP2 is set to
Which would be above what EG4 suggests. I personally would adjust that down as well, but:
All the internal settings are solely fallback/redundant.
As long as the BMS is connected to the GX, DVCC is enabled and the chargers are in turn also connected to the GX, then their internal charging algorithms are not being used. So whatever you set on the MPPT for example, does not matter.
Which is why you again received alarms.
Its the BMS through DVCC that controls the charge.
This will let the system charge up to this point, and is essentially what Mike meant
Now its possible that 27.6V is not quite enough to trigger the BMS to balance, but its worth a try. Let the system charge to that voltage, observe the min/max cell voltages, then gradually increase the limit until the recommended absorption voltage is reached. From that point on this manual limit is no longer needed.
Nick is the Victron Expert and certainly he is right saying it’s your responisibility
It is not recommended to continuously/long-term operate a LiFePo cell at 3.6V or above due to accelerated chemical degradation at this level.
A ‘heathy’ voltage is 3.35 - 3.4V, ref your manufacturer spec for EG4 27V/8 = 3,375V.
Unfortunately for balancing the recommended voltage range is (3.4 -) 3.45V or above since there a difference in state of charge results in a cleary perceptible difference in voltage (‘knee point’, see the diagram above).
So we are in some kind of dilemma. You mentioned cell voltages 3.41V to 3.62V…
-> From my point of view a good and more healty advice for/during balancing might be to keep the charge voltage on a level that the system can always reliably(!) identify the highest cell and pull that down by applying the passive balancer load.
So try lowering the charge voltage till the highest cell is above 3.5V (also the voltage where the balancer gets activated needs to get taken into account - check the manual). This will also eliminate the OV warning (usually 3.6V). But doing so means to frequently monitor the individual cell voltages and re-adjust the charge voltage accordingly, since the more the cell voltages equalize the more charge voltage needs to get applied to keep a level above the ‘knee point’ of the characteristics to allow the reliable identification of the difference in charge.
Thanks, Nick. I manually adjusted the DVCC yesterday and that has, so far, seemed to solve the issue but I’m holding my breath. The batteries reached full charge about an hour ago and so far no warnings. Everyone here as been extremely helpful and I am grateful for that.
After the adjustments I made to the DVCC yesterday, the batteries are now fully charged and I’m looking at current high and low cell voltages of 3.455V and 3.465V. I’ll be keeping an eye on it throughout the day. It’s quite sunny today so if problems persist they’ll probably manifest this afternoon. Thank you for all of your help and suggestions. This has been very educational for me. Our previous lead-acid/Renogy MPPT system was pretty simple and I really didn’t know what I didn’t know until I got this new system up and running late last week. Part of my confusion was understanding which BMS was controlling the absorption and float voltages and overriding the other and why those setting were greyed out on the charge controller settings. And there was also the learning curve of understanding what and how I could make changes remotely with the tools Victron provides.
