@Zheng-Han I'm not sure I need a BMS. The system has a smarter inverter/charger for AC and a MPPT solar charge controller. I'm really just looking for a way to monitor DC voltage in at several points in the system (maybe as many as ~20 -- 16 batteries, 3 PV strings). In my case, the batteries in my array are sealed lead acid. I found this BMS Voltage Display Energy Transfer Equalizer, Lead Acid 4/ 8 /16 string 36V 48V 60V Lithium Battery Protection Plate think we would have any luck connection this to an onion somehow? think it would do what I'm describing?