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

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.

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.

RS485 BMS not communicating? Check each connection layer

An RS485 connector does not confirm that the BMS and inverter use the same pinout or message protocol. Use the exact model and hardware revision before changing a cable or communication setting. The wiring diagram and manual guide separates model documents from generic inverter topology.

1. Find the BMS model in the model-specific pinout tables, or use its exact manual in the downloads library if it is not listed. For a P-Link installation, confirm the documented cable and inverter socket; the RS485-P service and parallel sockets are not the RS485-EXT inverter socket.
2. With power isolated, confirm connector orientation, RS485-A and RS485-B positions, cable continuity, and the required ground or shield connection. Select a communication cable by documented model and port, not connector shape alone.
3. Match the selected inverter protocol profile, firmware, baud rate, parity, stop bits, device address, termination, and master-slave roles to the documented requirements. A working physical link cannot compensate for a different application protocol.
4. Before relying on automatic battery limits, confirm that the inverter receives plausible SOC, voltage, current, alarms, and charge or discharge limits. If the exact pinout or protocol is not documented for your combination, request a compatibility check with both model labels and firmware versions.

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