good morning everyone, I installed a 200Ah Victron lifepo4 battery and a 12/200 smart bms on my boat. I also have 3 Victron solar regulators that I wanted to connect to the engine battery so as to use the 12/200 bms to disconnect the charging of the lifepo4 battery when the voltage reaches the threshold preset by me. Yesterday I went out for the first time, I started the engine and after a bit of navigation I noticed that when the set threshold value was reached, the bms disconnected the charging of the lifepo4 and immediately the voltage of the engine battery began to rise up to 16v. I disconnected the charging of the 3 Mppt and the voltage dropped. In practice it is as if the Victron MPPT algorithm did not know this eventuality, as if it sensed a sudden drop in the current request as if it were a resistance and dangerously increases the voltage of the engine battery to which the regulators are connected. I hope that the Victron technicians will be able to solve it, in the meantime either I install a battery protect for the solar panels or I will have to turn off the MPPTs when sailing under engine power
with mppt regulators deactivated, when the bms disconnects, the engine battery still goes up to 14.8v, but it’s already better this way. However, I’m afraid of this continuous disconnection and connection of the bms, I hope nothing happens
Could it be the presence of a 200A fuse that I put on the alternator-engine battery line?
I finally unplugged the solar regulators and everything started working properly again.
Do you have a BMV/SmartShunt and GX device with DVCC activated?
yes, both, but what would be dvcc?
Edit dvcc not actived
Did you configure a VE.Smart network between the devices?
Yes, with victron app
Which devices did you add to the smart network?
Maybe add a schematic of your system.
You might have to remove the MPPTs or the shunt from the network.
If the MPPTs get a voltage transmitted from the shunt they try to increase the that voltage by increasing there output voltage.
I have 3 mppt regulators, a ip43 phoenix charger and the smart shunt. The voltages are the same in all the measurements of the individual devices, so no voltage drops. now I try to activate the dvcc so we’ll see what happens, but I’ll be back on the boat in a week, I’ll update you. thanks for the moment
No, that will result in the same problem if the MPPTs are not connected to the same battery as the shunt.
If you have connected the MPPTs to the starter battery they have to run in stand-alone.
ok ok. So what can cause this problem?
And finally I did not understand if you wanted the mppt on the system+ port of the bms smart 12/200, would I have the bms protection that will disconnect the charge when the voltage reaches the maximum? Because from the bms 12/200 there is no possibility of regulating except the maximum voltage from the alternator port. I am quite confused on how to connect these mppt regulators
I connected the solar regulators on system+ of the bms 12/200 and now the system+ port reaches 16v with the solar regulators active and the engine running, despite the bms disconnecting the alternator. The voltage of the system+ port varies continuously, from 13.3v to 14.6v if I connect only one solar regulator, if I activate 2, instead it also reaches 16v. With the engine off, everything stabilizes and no problem. I’m going crazy
The manual shows how to connect it:
Disable the Smart Network or at last remove the shunt from the network.
The shunt is sending a voltage that the MPPT wants to reach.
If the BMS blocks the current into the battery it causes the MPPT to increase it’s output voltage to raise the voltage transmitted by the shunt → the voltage at the shunt isn’t rising → MPPT increases it’s output more and so on…
but this way I should connect the solar regulators with the vedirect port to the charge disconnect port and I would take advantage of seeing the solar regulators on the Cerbo GX
[anyway now I have unfrozen the smart shunt from the network, later I will try to see what happens
Hello Frank. Your setup is close to what I had on my boat, which worked well. I was using the Smart BMS CL 12/100. I wonder if you can get the same result I did?
I had the three MPPTs connected to the bus bars for the LiFePO4 house battery, not to the engine start battery. My Smart BMS CL 12/100 allowed charging current to flow from the house battery to the engine start battery (via the alternator cable) whenever the voltage at the LiFePO4 post on the BMS was greater than 13V. In effect, the BMS was acting as a battery to battery charger. I’ve been looking at the manual for your Smart BMS 12/200 to see if this functionality is described. I haven’t found it. It might be undocumented.
My suggestion for you is to move the output from your MPPTs across to the house battery bus bars, restart everything and turn on DVCC. Then, with no separate charger working for your engine start battery (no shore power), measure the voltage at its terminals. Compare with the system off, or better, with the battery negative disconnected. Is the BMS sending charge to your engine start battery? If yes, this means the solar panels are charging the engine start battery, via the house battery and BMS.
If it isn’t, install an Orion 12-12V battery to battery charger, to charge the engine start battery from the house battery. Inexpensive. I didn’t need one.
Also, as you’ve guessed, it would be a good idea to use a Smart Battery Protect (my preference, for power consumption reasons) or Cyrix Li-Load to cut the charging from the MPPTs if the house battery asks the BMS to do this. I’m sure you already have a Smart Battery Protect to cut loads if the battery is discharged too much.
Edit: Nope - I’ve just noticed in the manual for the Smart BMS 12/200 that the functionality I’ve described from the Smart BMS CL 12/100 is not provided. On page 2 at para 2.2 there is, ‘In addition, no current can flow back from the lithium battery to the starter battery, which prevents the lithium battery from being deeply discharged.’ I would still run the test I’ve described, to see if solar charging via the MPPTs to the house battery bus bars, to the BMS, to the engine start battery is occurring. While I’m sure the BMS will protect the house battery from being flattened, it might also allow current to flow if voltage is above a certain value. But perhaps you need an Orion.
I’ll add this as a new reply as well.
Nope - I’ve just noticed in the manual for the Smart BMS 12/200 that the functionality I’ve described from the Smart BMS CL 12/100 is not provided. On page 2 at para 2.2 there is, ‘In addition, no current can flow back from the lithium battery to the starter battery, which prevents the lithium battery from being deeply discharged.’ I would still run the test I’ve described, to see if solar charging via the MPPTs to the house battery bus bars, to the BMS, to the engine start battery is occurring. While I’m sure the BMS will protect the house battery from being flattened, it might also allow current to flow if voltage is above a certain value. But perhaps you need an Orion.
the charge from the service battery to the engine is not there, I have already checked. the next step is to disconnect the smart shunt from the veSmart network, because I fear that this could be the problem, because perhaps it reads a different voltage and pushes the solar regulators to increase the voltage. Now that the solar regulators are connected to the system+ port and no longer on the engine battery, I had noticed that the system+ port was protected from receiving high voltages from the solar regulators, and jokingly the shunt from the network I immediately noticed that it no longer happened, but I could not do further tests because in the meantime I had arrived at port. now I only have the problem of the alternator which however when the bms disconnects it recharges it, the voltage rises to 14.8v on the engine battery, still a bit high, and especially if the number of engine revolutions is ridiculous, strangely it also rises to 15.3v until it drops to 13v when you put the engine at idle, but here it may have something to do with the alternator regulator. Finally I still haven’t understood if the system+ port also acts as a battery protect for charging as well as for low voltage