I have a Vatrer Power self heating 200ah lifepo4 battery installed in my camper. I generally use the solar panels on the roof of the camper to charge the battery. The battery has a bult in Bluetooth BMS . I use the OverKill app to monitor the SOC etc. I recently installed a 500 amp Smart Shunt into the system. The negative side of the battery is connected to the battery side of the shunt. There are no other negative connections to the battery. The system side of the shunt connects to a bussbar which has the rest of the negative connections for the system connected to it. The only negative that is not connected to that bussbar is the negative wire from the solar controller. I don’t remember exactly where that is connected, but it must be grounded to the frame somewhere. My issue is that when I have things in the camper running strictly off the battery , the bluetooth app reading the battery bms will give me a soc in the morning before the sun starts recharging the battery, of say 88%, but the SmartShunt will be at 100%. The voltage readings will match between the 2, but not the SOC. I have tried tweaking the setting vis the Victron Connect, but nothing seems to work. I have also on several occasions manual reset the SOC in the Victron settings to match the OverKill app, and the SOC on th Victron app hits 100% a LOT faster than the OverKill. I don’t expect them to both be exactly the same, but for it to be at 100% in the morning when things are draining the battery, something is not right. I have attached a screen shot of the battery settings.
The settings in your SmartShunt appear OK which is good as these can often cause an issue. I would however use 4% for the tail current, but that is not the cause of your issue.
The other reason for what you are seeing is the MPPT negative being connected to your battery and bypassing the shunt. If the MPPT negative goes to ground then your ground connection to the battery and common negative to the starter battery also have to be on the system side of the SmartShunt.
See link below
One thought with my system and a Fogstar Battery the battery BMS ignores small currents under about 1.5 amp.
Consequently as there are small discharges (5 watts running the Cerbo) the BMS ignores it but it registers on the shunt. This can lead to the BMS reading 100% and the Shunt reading 60%.
Similarly when charging the shunt registers all the small ( under 1.5amp) bits of solar whereas the BMS doesn’t leasing to the shunt reading 100% and the BMS reads some fanciful figure known only to itself.
Its worth checking if the BMS in your system does the same. Under the Fogstar badge mine is a JBD BMS.
Actually it’s a PWM controller, but I am sure it is not going to make a difference. I am going to trace the negative from the controller and run it directly to the buss bar that the shunt is running to. Heading out of town Wednesday so I am not sure if I will get to it before then or not. I will report back when I can.
Want to report back. I initially thought that the charge controller was grounded to the frame of the travel trailer, but upon further investigation, it is connected to the negative bussbar on the system side of the shunt. Not sure where to go from here. Is it possible that there is an issue with the Smart Shunt itself?
Did you confirm if there is a chassis connection to the battery negative or the bus bar / system side of the shunt.
The battery negative is connected directly to the battery side of the shunt. No other connections to the battery. The system side of the shunt is connected to a busbar and all grounds or negatives are connected to the bussbar.
Everything seems OK, t he SmartShunt is usually reliable. Do check that in the settings it is correctly set as a 500Amp SmartShunt not one of the other ratings. The SOC from some of the cheaper batteries is less than reliable so that may be the cause of the mismatch.
