In short
- UART is a short, low-level link, meant for the Bluetooth module or a PC adapter right next to the board.
- RS485 is the dependable link for longer cables and for monitoring; many boards get it through JBD’s RS485 module.
- CAN is usually the inverter link on JBD inverter BMS; leave it to the inverter and monitor over RS485.
JBD makes a long list of boards: small SP boards for 4S to 24S packs, and larger inverter BMS such as the UP16S series. Their communication options differ, and the connector on yours decides what you can plug into it. Here is how to tell them apart.
UART: the short link next to the board
Most SP boards have a small multi-pin connector for UART. It carries logic-level serial data and is meant for short distances: the Bluetooth module, or a USB adapter to a PC running JBD’s software. It is not designed for a long cable through the house, and plugging something into it that expects RS485 does nothing useful.
On many SP boards, the Bluetooth module and the RS485 module use this same connector. That is why some owners have to choose one or the other, and why it is worth checking before ordering anything.
RS485: the link built for distance
RS485 uses two wires carrying the signal as a difference, which makes it reliable over several metres and in electrically noisy places, such as next to an inverter. Larger JBD boards and JBD-based batteries often have it on an RJ45 socket. SP boards get it through JBD’s RS485 module, a small board that turns the UART link into RS485.
This is the port a permanent monitor should use. It lets a box sit a few metres away, behind a wall or outside a battery case, and read the BMS around the clock.
CAN: usually for the inverter
On JBD inverter BMS, CAN is typically the link that tells the inverter how much it may charge and discharge. That conversation matters for the safety of the pack. Leave it alone and read the BMS from another port.
How to identify yours
| What you see | Likely link | What to do |
|---|---|---|
| Small multi-pin connector, Bluetooth module plugged into it | UART | The RS485 module is needed for a monitor |
| RJ45 socket marked RS485 | RS485 | Plug the monitor straight in |
| RJ45 socket marked CAN | CAN | Keep it for the inverter |
| Nothing printed, or not sure | Unknown | Send a photo before ordering |
What JBD Monitor needs
JBD Monitor reads RS485: the RJ45 port on boards that have it, or JBD’s RS485 module on SP boards. Tell us the reference printed on your board when you order; we test that exact combination before shipping, and if your board turns out to need something else, we say so before you pay.
Common questions
Can I wire RS485 straight to the UART connector?
No. The signal levels are different. The RS485 module is the part that converts one into the other.
Will the RS485 module stop my Bluetooth app from working?
On boards where both modules share one connector, you choose one. Tell us your board and we tell you how yours is laid out.
Can the box read the CAN port instead?
It is designed to read RS485 and leave CAN to the inverter. That keeps the inverter link exactly as the installer set it.
