Discrepancy Between JK-BMS Current Readings and Victron Shunt During High PV Load

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:

  1. What could be causing this false discharge reading on each JK-BMS?
  2. Could this be due to ground loops, shared GND between MPPTs, MultiPlus and BMSs, or some interference?
  3. Has anyone else experienced this behavior with JK-BMS in multi-pack setups?

Any suggestions or insights would be greatly appreciated!

Thanks in advance.