Hello everybody
I have a system made up of multiplus II 5000/48, pv inverter fronius primo 4.0, 6 Q-cell panels (580 watt each), and a 4 kwhr BYD lithium battery.
I am suffering from rebooting of the system for few repetitive times (3 to 4 times per day, each time may reboots about 5 to 6 reboot) whenever the battery is full, i noticed at the same time with this issue there is a High battery voltage alarm and High DC ripple.
What i should do to solve my problem?
Is the dc ripple on system restart or the cause of system shutdown?
You could try limiting the charge voltage in DVCC to 0.2v lower (for now) and see if that helps. It seems as though the bms is a little unhappy with something.
Charge voltage in DVCC is 55 v, do u need me to set it as 48.8 v?
What do u mean by ur first question?
I saw on VRM app that there is alarm about high battery voltage and high dc ripple which may cause my system to restart few times repetitively.
Set it to about 54.8 or 54.6v and see if it helps with the high voltage alarms. And limit charge current down to it as well. They may be charging too fast to balance themselves.
The dc ripple is then caused by the bms disconneting and reconnecting to prevent charge @dray22explained nicely.
With a slightly undersized battery these issues are seen often. So if you are able add more.
Does lowering the charge voltage lead to lowering absorption voltage?
You asked me to limit the charge current, can you tell me how?
I really appreciate your help
Thank you
And i still have the same problem
What does the VRM say the system is charging the battery voltage to? Is it obeying the DVCC.
Hey, whenever i set charging voltage to 54.6 , I eliminate most of the problem, can I decrease it more to 54.4-54.2 ?
Whenever the battery is full and the charging boltage reach 54.5, the lowest cell voltage is 3.35 and the highest cell voltage is 3.58
Thank you
the lowest cell voltage is 3.35 and the highest cell voltage is 3.58
That's a huge difference. Keep the battery for longer periods of time close to full, so that the BMS can try to equalize the cell voltages.
If needed, you can lower the charging voltage and as the cells get closer in voltage at the top (over time), gradually increase it back again.
You might need to decrease the charging current, too.
Watch that no cell gets above 3.6V.
How low you discharge the battery? If very close to empty, this can cause a cell voltage imbalance.
Have you run through the setup steps listed here to confirm nothing was missed?
https://www.victronenergy.com/live/battery_compatibility:byd_b-box
I don’t know what the installer do, but I realize now the 4 kwhr BYD firmware is 1.22 while the file you sent suggest to have at least 8kwhr in off grid case with a firmware not less than 1.3 or 1.4.
The file suggest to have 4kwhr for multiplus II 3000/48
if i remove one panel (so i will still have 2900 watt at all) , I have multiplus II 5000/48 , do u think it will be compatible according to that file you sent before.
I had high dc ripple when my LifePO4 batteries voltage was getting full and spiking. This causes the charging to start and stop over and over very fast causing the ripple. You may need to lower absorption voltage until the behavior stabilizes and can complete absorption phase without the voltage spike and float.
You may get something out of my little story here...........https://community.victronenergy.com/questions/129138/quattro-shutting-down-lithium-batteries.html
I hope it may help a bit.
When under full load what is your DC ripple?
Use VE Config when running the test and see what is shown there.
And to control the charging from grid
Your batteries may not balance at that voltage. There is a minimum that is needs to reach for the cells and battery to be healthy. If they don't balance your problems may get worse.
@Khaled ....You seem to have a problem similar to what I wrote about and copied below. Reduce your Absorption voltage until the system stabilises. Keep reducing it to prove the battery BMS is the culprit. You need a stable system to just make sure the battery BMS is the problem before you can move forward. The time when the BMS will cause havoc is during the absorption charging phase becasue the battery terminal voltage is highest then. If you can get past Absorption phase and onto float it should be ok because the voltage is lower in float phase. The battery BMS is causing a variation in DC voltage that the Victron unit interpets as "DC Ripple". If the problem is the same as I saw it is not really DC ripple. It is interpreted as DC Ripple and that is what the warning says.
Just an update to the issue earlier raised in this post. The system is stable and charge current has now been increased to 120 amp and all batteries have been connected back into the house bank.
The reduction of the absorption voltage from 29.2 volts to 27.6 volts has presumably stopped the internal Battery BMS units activating the cell overcharge protection. As a matter of record, 29.2 Volts is perfectly within the battery suppliers specified voltage level. I have included a relevant VRM screen shot to indicate that prior to the reduction, the terminal voltage was bouncing all around the place. After the reduction we have established relative calm regarding battery terminal voltage.
We can also see that while the BMS units were creating chaos, the DC Ripple warning would occasionally appear. While this manifests as a DC Ripple warning it is actually DC voltage variation, a subtle but important difference.
While this maybe basic for seasoned lithium installers, I was interested to see that 1.6 volts of difference in absorption voltage setting is the difference between calm and absolute chaos and mayhem. It caused the Quattro to cycle continuously from "off" to "bulk" to "absorption" and "off" again. Occasionally the Quattro would lock itself out in "Fault" mode. All of this without any fault notification except for an occasional wrongly attributed DC Ripple warning.
With more cheap lithum batteries being installed maybe this may become more common. It could perhaps be something Victron may be able to identify as an excessive "DC voltage variation" rather than a "DC Ripple" warning. It that warning were implememted it may help with troubleshooting if that type of warning is appearing a reduction in absorption voltage could be tried to redcue BMS actvity when battereis are fully charged.
With 4 kWh battery, AC coupling rule is 1.5 kWp for every 4.8 kWh battery. Inverter 1:1 is fine, but you going to have trouble with voltage, unless the fronius is on the input of MP? Unlikely. So with those panels (6x580) you need minimum 11 kWh battery. When it is full it may still present a problem when grid is disconnected.
