JK BMS inverter communication: CAN, RS485, pinout, and protocol

Inverter protocols supported by the JK-PB series

This verified factory document lists 14 protocol profiles covering 12 inverter brands over CAN or RS485 for its documented JK-PB scope. It does not establish the same protocol coverage for every other JKBMS series.

JK BMS CAN and RS485 pinout

Pin assignment follows the exact model, not the series name. Two boards can carry the same A1254WF-4A connector and number it from opposite ends: most models put CAN on pins 1 and 2, but JK-BD6A8S-10P, JK-BD4AxxS-6PRG and JK-WB2A8S-30P put CAN on pins 3 and 4. Applying the wrong table wires CAN into the RS485 pair. Find your model in the lists below before wiring anything.

Connecting a board-level BMS through the P-Link interface board

A JK-PB energy storage BMS presents RJ45 sockets directly. A board-level BMS does not: its communication port is a 4-pin header, and the inverter is reached through a P-Link-CR interface board. The signal path is:

BMS P3 → reverse cable → P-Link P2 → CAN or RS485-EXT socket → inverter

The cable between the BMS and the P-Link is a reverse cable

The two 4-pin headers are numbered from opposite ends, so pin 1 on the BMS meets pin 4 on the P-Link. The cable supplied with the P-Link-CR is specified for exactly this: GH1.25-4P to GH1.25-4P, reverse, 30 cm (supplied with the P-Link-CR).

Which P-Link socket the inverter plugs into

The board carries four RJ45 sockets and they are not interchangeable. Only two of them reach an inverter.

Pin numbers are per socket, counted on the RJ45 plug. Note that the CAN socket uses pins 4 and 5, which is the same arrangement most hybrid inverters expect for a battery CAN link.

Sources: JK-B2A8S-20P maintenance manual V19.2.1, connector P3 (optional); P-Link-CR interface board manual V1.0, connector P2.

Separate physical interface from communication protocol

CAN and RS485 describe electrical communication methods. The actual battery-inverter integration also requires a compatible message protocol, data map, timing, fault behavior, and device role. Two products can use the same connector and still be unable to exchange useful battery data.

Use the CAN vs RS485 guide for the interface differences, then verify the exact protocol supported by the selected BMS and inverter.

Compatibility requires every layer to match

Understand what the communication cable does

A communication cable connects the required pins between the BMS and inverter. It may adapt connector formats or pin assignments, but it does not create a protocol that the two devices do not support.

Compare available products on the JKBMS inverter communication cable page.

Choose the BMS series with communication in mind

Start with chemistry, series count, current, balancing, and safety requirements. Then confirm whether the selected BMS model supports the communication interface and inverter protocol needed by the project.

The JK-PB Series is positioned for energy-storage applications that may require display and inverter communication features. Compare the exact product specifications rather than assuming every model within a series has identical interfaces.

Plan CAN termination and RS485 topology

For CAN, confirm bus topology, cable type, shield handling, cable length, bitrate, and termination at the two physical ends of the bus. Avoid creating unintended stubs or duplicate terminators.

For RS485, confirm two-wire or four-wire operation, device addresses, biasing, termination, master-slave roles, and whether multiple devices share the same bus.

Commission the communication before relying on automatic limits

• Verify the BMS and inverter firmware versions
• Select the correct protocol profile on both devices
• Confirm connector orientation and pinout with power isolated
• Check CAN-H/CAN-L or RS485-A/RS485-B continuity
• Verify required ground or shield connections
• Confirm bitrate, baud rate, address, and termination
• Check that the inverter receives SOC, voltage, current, alarms, and charge or discharge limits
• Test communication-loss behavior and safe fallback settings
• Record the final wiring and software configuration

Information needed for compatibility review

• Exact JKBMS model and hardware version
• BMS firmware version
• Inverter brand, model, and firmware version
• Required CAN or RS485 interface
• Selected inverter protocol profile
• Connector photographs and pinout documentation
• Cable length and installation environment
• Single battery or parallel battery architecture
• Required quantity and destination