Power the board before expecting a Bluetooth signal
A JKBMS board is powered from the battery it manages, not from the load side. If the cell-voltage harness is not connected, or the battery is below the board’s operating threshold, the Bluetooth module does not advertise and the app cannot see the device at all.
Before troubleshooting the app, confirm the board has power: the balancer or status indication on the board should be active, and the cell-voltage harness should be seated in the correct order for the series count of the pack.
Bluetooth holds one connection at a time
The single most common cause of a device that appears in the list but refuses to connect is that another phone, tablet, or display is already connected to it. A Bluetooth Low Energy peripheral of this type accepts one active client.
Close the app on every other device that has previously connected, and disconnect any wired or wireless display accessory that also talks to the board, then retry.
- Close the app fully on other phones rather than just locking the screen
- Power down or disconnect a connected LCD display accessory
- Remove the stale pairing entry from the phone Bluetooth settings and rediscover
- Toggle phone Bluetooth off and on to clear a half-open connection
Grant the permissions the scan actually needs
Android requires location permission, and on newer versions a separate nearby-devices permission, before an app is allowed to scan for Bluetooth Low Energy peripherals. If either is denied the scan returns an empty list with no error, which is easily mistaken for a hardware fault.
Check the permissions in the phone system settings for the app rather than only inside the app, and confirm that battery-optimisation settings are not suspending it in the background.
Read settings before changing them
Protection thresholds, balancing parameters, capacity, and series count are all writable from the app. Changing them without recording the original values can leave a pack unprotected or prevent it from charging.
Record the existing configuration before editing anything, change one parameter at a time, and confirm the value against the manual for your specific model. The exact parameter set differs between the JK-BD, JK-PB, JK-B1A, and JK-B2A families.
When the app is not the right tool
For a permanently installed system, a wired display or an RS485 or CAN link to an inverter is more reliable than a phone connection, which is limited by Bluetooth range and holds only one client.
Use the app for commissioning, configuration, and diagnostics, and use a wired interface for continuous monitoring and inverter integration.
Questions this raises most often
The board is most often unpowered, already connected to another device, or the phone has not been granted location and nearby-device permissions needed to scan for Bluetooth Low Energy peripherals.
No. The Bluetooth module accepts one active connection, so any other connected phone, tablet, or display accessory must be disconnected first.
Model manuals and accessory documentation are published on the downloads page of this site. Confirm the parameter set against the manual for your exact model family before changing protection settings.
No. Bluetooth is intended for commissioning and diagnostics. Use a wired display or an RS485 or CAN link to the inverter for continuous monitoring.
Take it to a part number
Ratings vary between codes that read almost the same, so settle the decision here and then confirm the figures on the product page for the exact code.