I have multiple Systems with Pylontech and Pytes Batteries running with CAN Bus connected to the Cerbo and they are detected correctly. DVCC uses the given Voltage and Current Limits for charging. But as SVS is forced off it uses the measurements of the Multiplus 2 and these differ by 0,1 to 0,2V to the measurements of the BMS. That is the reason why these Batteries have Problems resetting the SOC to 100% at the End of Charge. Is there a reason for this behaviour? Can we please get the option to turn SVS on to use the measurements of the BMS for charging?
@Tueddelkopp Ensure the system is configured as per attached to ensure the battery BMS voltage is used as opposed to the inverter readings. You can select which.
The Pylontech is correctly selected as Battery Monitor. Nevertheless DVCC uses the measurement of the Multiplus. I have one other System with a Gobelpower Battery and there SVS is switched to on and all works as expected.
1 Like
Speculation: The voltage provided by Pytes when the BMS prevents charging is the internal battery voltage, and not the voltage presented at the terminals. The inverter may keep raising its voltage, and it runs away. I’ve seen this with other batteries and SVS needs to be off for safety.
This may or may not be the reason, I don’t own any Pytes.
Ok, that makes sense. For these cases a Workround should be implemented. If the two voltages differ too much use Multiplus measurements, otherwise use BMS measurements. Another Option could be to add a changable Offset of 0 to 0,3 V or so.
Is there a possibility to overrule the “forced off”?
Assuming the voltage measurement accuracy of both devices is within 0.1V, the only way to see more of a voltage difference is V=IR of the cables from the batteries to the inverters. Meaning at high charge current levels, the voltage drop could be significant.
Usually when absorption charging occurs, it tapers off the current, so the voltage drop should also decrease as it gets closer to full.
See if you can compare the voltages from the inverters and battery when no current is flowing.
If it isn’t within 0.1V, then the assumption above does not hold.
The measurements of the Multiplus are absolutly correct compared to the busbar and battery terminals with a known good multimeter. Nevertheless i have to charge till the BMS reaches its expected values to reach the 100% SOC. Its not Victrons fault, i am simply searching for a solution for this.
1 Like
I just checked my shop system and we’re 0.2V different between what the Multi’s see as battery voltage and what the Pytes batteries report.
This system uses Pytes E-Box 48100R batteries and the SOC resets to 100% when the batteries fully absorb. I just checked another system with Pytes V5° batteries and that system has reached 100% SOC for several days in a row in the last week.
I’m curious, how did you conclude that DVCC is using the measurement from the Multi instead of the BMS?
Thanks
In my case its the Pytes E-Box 48100R as well. It stays the whole day at 99% with a Voltage reading from the BMS of 56,3V and the CVL from the BMS is 56,4V. The Multiplus reads 56,4V and does not charge further.
If i then switch BMS Control off and set the Charge Voltage to 56,5V the Pytes directly sets 100% SOC and starts lowering the CVL to protect the battery from idling at this high Voltage (nice function). I never get the 100% SOC with BMS Control active, thats the reason why i am searching for a solution as i want the BMS to lower the CVL at Full charge.
The Pylontechs dont lower the CVL at 100% SOC so functional and from “real” SOC standpoint it doesnt matter that much there. But it would be nice to get to 100% there either.
That’s interesting that your behavior is slightly different than mine. I was looking at the summary pages on VRM but I’ll go and look at SOC reported on the GX device. Maybe it’s a rounding error when posted to VRM.
Also a system with 4x Pytes 48100R here.
At the moment there’s a 10A ~580W power draw from the batteries and voltage difference between Pytes and my Quattros is 0.01V.
When charging, the difference can go up to 0.3V but so far no problems to get the batteries charged to 100%.
Next to my Quattros I also have a Victron MPPT charging the batteries.
Batteries are running Comm Version: V2.0
Main Soft Version: SPBMS16SRP2111V1.3.32
Boot Version: V1.14
Do you have a GX device? In the venus os there are some dbus properties that might be helpful, at least for testing:
com.victronenergy.system / Debug/BatteryOperationalLimits/VebusVoltageOffset
and
com.victronenergy.system / Debug/BatteryOperationalLimits/SolarVoltageOffset
I believe if you increase those by 0.1 it would cause the charger to put out 0.1v higher than the requested voltage, which might allow it to trigger the battery to reach 100% and then reduce the charging volrage.
Setting the parameter requires you to log into the venus os terminal and use dbus-spy, so it’s not exactly convenient unless you are familiar with ssh.
Yes i have a GX Device. Thats what i am searching for. These Parameters are changable by a custom control in Node Red. I will try that next time my battery is close to full charge.
Thanks
I tested this today and it just worked. I set the Vebus Offset to 0.1 and the battery charged to exactly the desired Voltage and after a short time it set SOC to 100%.
2 Likes
The SVS is Shared Voltage Sense used by Victron devices to have a common sense of battery piles or BMS piles voltage value. For ex all MPPT chargers and inverters/charges will share these values. But this not suppose , if activated , to have same measurement voltage at battery BMS or at inverters/chargers. Just consider that from inverter battery plugs till BMS you have cables of 25sqmm and 35-50sqmm that are each at least 2 meters long + power switches + fuses and you got a battery stack/pile current of 50 Amps, that means that a deviation of 0,1V is about 20 mili-ohms in resistance on all this cable chain , value that is quite normal. On the other hand the battery pile from Pylontech uses its own mechanism to predict the 100% or 20% capacity based on temperature, predictive charging/discharging and not directly on absolute voltage. If you have limit bulk charging to 52,4v (and absobtion to 52v + float 51v) for Victron devices this means 100% charging but for battery pile BMS is somewhere around 97-98%.
Victron Multiplus-II has a Voltage sense connector and a special cable (in the pack) to measure and compensate possible cable losses during charging in both ways (+ and -) with a a maximum of 1v. The cable will be connected directly to battery and inverter plugs (+ and -). for this purpose.
There is no need to try adjust them, this will be adjusted by Cerbo GX for all Victron devices that share the same battery pile.
This topic was automatically closed 14 days after the last reply. New replies are no longer allowed.