Would like to add a third party battery monitor to complement the Cerbo. Is it ok to add this secondary shunt on the battery side of the Lynx BMS (orange arrow in photo)?
Any reasons not to do this?
I currently have it on the distribution side, but it slowly loses sync with the Cerbo SOC over days/weeks. I think this is due to the BMS Aux loads which bypass the distribution side and come out via the pins at the bottom. Hence wanting to move the shunt location.
I can not see why it would not work. Connect the positive of the second shunt to the output side of the BMS so if the BMS shuts down then it will stop the parasitic draw of the shunt.
I notice in your photo that there is a small negative wire on the battery bus bar, any current flowing in this will not be counted, neither will the parasitic draw off the positive cable be isolated on BMS shutdown.
However, having said all this, I would expect to see some a drift between 2 battery monitors in series especially if they were different manufacturers and the batteries go for some time between 100% synchronisations. There is the issue of inherent accuracy, they will have different innacuracies, the SOC algorithms may be different especially in implementation of Peukert, you would really need to compare discharged Ah rather than SOC.
