Hello everyone,
I’m currently running an off-grid system consisting of:
- 3x Victron MultiPlus 5000VA (single-phase)
- 1x RS450/200 SmartSolar MPPT
- 1x MPPT 150/45 + 1x MPPT 250/100
- 75kWh LiFePO4 storage (5x DIY 48V battery banks)
- Each battery uses a JK-BMS with Bluetooth/RS485
- Full system monitoring integrated in Home Assistant and Victron VRM via Venus OS
Each JK-BMS reports charging/discharging currents accurately when the system is idle or lightly loaded (±20–30A). However, I encounter a strange issue under high PV load:
When I start charging my EV (7.2kW), and the MPPTs are covering the entire load (float voltage is correctly maintained), each JK-BMS shows a discharge current of around –20A, even though the Victron SmartShunt reports near-zero battery current (±1A), which is confirmed via clamp meter measurements both on each battery and on the common busbar.
In summary:
- VRM & clamp meters show correct current: ~0A (float maintained, PVs power the EV directly)
- Each JK-BMS falsely reports ~–20A discharge
- PV production and voltage regulation are normal
- The discrepancy appears only when all loads are PV-powered and system is in float
- All BMSs are paralleled with common positive and negative busbars
- JK-BMS shunts are on the negative line (default)
I’m wondering:
- What could be causing this false discharge reading on each JK-BMS?
- Could this be due to ground loops, shared GND between MPPTs, MultiPlus and BMSs, or some interference?
- Has anyone else experienced this behavior with JK-BMS in multi-pack setups?
Any suggestions or insights would be greatly appreciated!
Thanks in advance.