Anyone else had grief with JK BMS dropping Bluetooth after a firmware update?

Updated my JK BMS (the 2A active balancer, 200A version) to firmware 11.26 last week and ever since the Bluetooth drops out constantly. It'll connect fine in the JK app for maybe 30 seconds, then just vanishes. Have to kill the app and reconnect every time, which is a right pain when you're trying to monitor charging from the house while the van's on the drive.

Setup is 4x 280Ah EVE cells in a 12V configuration, so it's nothing exotic. Was rock solid on the previous firmware — can't remember the exact version but it was whatever shipped on the unit back in March. I've tried it on two different Android phones (a Samsung A54 and an older Pixel 3a) and the behaviour is identical on both, so I don't think it's a phone issue.

Has anyone managed to roll back the firmware, or found a workaround? I've seen some chat on a couple of Facebook groups suggesting there's a known bug but I can't find anything concrete. Would be good to know if others are seeing the same thing before I fire off an email to the supplier.

HighlandDweller | 847 posts | ⚡ Solar Addict

@AngliaCruiser had exactly this with mine after 11.26 dropped - absolute nightmare. What sorted it for me was rolling back to 11.24 using the older APK version of the app (grab it from the JK official Telegram group if you haven't already - they keep archived versions there).

Worth checking whether your phone's Bluetooth is BLE 5.0 compatible as well, as 11.26 seems to have changed something in how it handles the BLE stack. My older Android tablet couldn't hold connection at all, but my newer phone was rock solid on the same firmware.

If rollback isn't an option, try toggling "continuous Bluetooth mode" in the BMS settings - buried in the advanced menu. Bought me another few weeks while I waited for 11.27 to sort it properly.

Midge52 | 203 posts | 🔋 Off-Grid Tinkerer

Same issue hit me on the 200A unit in my static. Rolled back to 11.19 and it's been solid since. JK's own Telegram group has a pinned message with the older firmware files — worth grabbing before they disappear.

One thing I noticed: keeping the phone really close (like 30cm) during the initial connect seems to help it stabilise before you walk away. Not a fix obviously, just buys you enough time to check cell voltages without it dropping mid-read.

@HighlandDweller did yours sort itself after rollback or are you still battling it?