I have a problem that I cannot seem to solve and hope someone might have some ideas.
12volt 210AH Silver Micromal lifepo4 Battery. Nothing apart from the shunt connected to the negative side of the battery ALL negatives connected to the shunt and have programmed the shunt as follows
Battery Capacity 210AH - Charged Voltage 14.0v - Discharge Floor 10% - Tail Current 2.00% - Discharge Detection Time 3m - Peukert Exponent 1.05 - Charge Efficiency Factor 99% - Current Threshold .10A - Time to Go Averaging Period 3m - Battery SOC On Reset Clear - State Of Charge 97.5%
The problem I have is that the SOC percentage on my Victron display and on the VRM portal is not correct according to the battery BMS for example today my shunt is reading 97.8% and the battery BMS is reading 85% this can be out as much as 30% I manually reset the SOC two days ago.
I believe the battery BMS is correct and the Victron is incorrect.
Any help would be appreciated as I have run out of ideas - Thanks in advance for any help.
Both should be calibrated to a voltage which correspond 100% SOC.
I have done this a number of times (as soon as the battery BMS stopped charging at 14volts I did a manual SOC sync).
Your shunt settings look to be OK.
There are many posts where the BMS in cheap/ basic drop in lithium batteries is not accurate, they have nothing as rigorous as a SmartShunt inside. I would always view the SmartShunt as the best as long as it is installed properly and confibured correctly.
Going by your screen name, I assume that this is in an RV, motorhome or caravan. One common issue with these installs that crops up repeayedly is the chasis ground or common negative to the starter battery, these must also be connected to the system side of the shunt.
Yes you are correct the system is installed in a Camper Van, The starter battery and house battery negatives both go to the system side of the shunt via the vehicles chassis. Are you saying that I have to have a copper wired link between the two (not relying on the chassis).
Thanks for your help.
No you do not need a separate link. I am just pointing out a common vehicle blind spot where a common fault is leaving the chassis ground on the domestic battery negative, not on the load side of the shunt because it is not seen as a “real” connection. It sounds like yours is OK so it may just be poor BMS. Some BMS boards need to learn the battery so may take a few cycles to become accurate.
