Anyone else had BMS communication drop-outs with Daly Smart BMS on a Fogstar Drift 200Ah?

Been running a 24V system in my garden office for about eight months — two Fogstar Drift 200Ah cells in series with a Daly Smart 24V 100A BMS, charged via a Victron SmartSolar 100/30 and a Victron Phoenix 24/800 inverter. The whole lot talks over VE.Direct to a Cerbo GX.

The Daly drops off Bluetooth randomly — sometimes every few days, sometimes twice in an hour. It reconnects fine, no tripped protection, SOC stays consistent. But the BMS data disappears from my dashboard for minutes at a stretch and it's doing my head in. I've tried the Daly app on two different Android phones, updated the firmware via the PC tool, even repositioned the BMS so it's closer to the office wall where my phone usually sits. Still happening.

Worth noting the Daly is about 30cm from the Cerbo and two Victron devices — wondering if there's RF interference in the mix, though I can't prove it. Has anyone actually switched to the UART/RS485 wired connection instead and found it more stable? Or is this just a known Daly Bluetooth bodge that I should stop fighting and replace with a JK or Seplos unit?

@VoltWill had exactly this on my narrowboat last winter. Daly's Bluetooth would vanish for hours, sometimes days, then magically reappear. Drove me absolutely mental.

Turned out to be two separate issues colliding:

1. The Daly app itself is genuinely terrible — it's known to lose the BLE pairing after firmware updates
2. Cable connection at the BMS communication port — mine had a dry joint from the factory

Fixed the dry joint with a proper re-solder, switched to xiaoxiang BMS app instead of the official Daly one, and 90% of the dropouts vanished overnight.

The remaining 10%? Still happens occasionally near my inverter when it's working hard — RFI interference I suspect. Shielding the BMS cable helped somewhat.

Worth checking your SmartSolar cable routing too — if it's running parallel to the BMS comms cable for any length, separate them.

Hey @VoltWill! Yes, had almost identical drop-outs on my Daly Smart last winter. Worth checking a couple of things first — the Bluetooth module on the Daly can be really temperamental with distance and interference. Mine was cutting out because my inverter was sitting too close and causing RF noise.

Also, have you tried the newer version of the Daly app? The older versions had genuine communication bugs that got patched.

One thing that made a noticeable difference for me was swapping to a proper shielded cable between the BMS and the UART connector rather than the flimsy one Daly supply. Cheap fix.

If it's not comms but actual BMS faults triggering, that's a different rabbit hole — what does the app actually show when it drops? Any overvoltage or temperature flags logged? That'd help narrow it down. 🔋

Seen this a fair bit — the Daly Smart BMS UART comms can get flaky when the onboard temperature drops below roughly 5°C, even if the cells themselves are fine. The Bluetooth module draws from the balance port, and cold increases impedance enough to cause resets.

Worth checking whether your drop-outs correlate with cold nights in the garden office. If so, a small self-regulating heat trace cable wrapped loosely around the BMS enclosure (not the cells) sorted it for me over winter.

Also — and @EllaPalmer may have covered this — make sure you're on the latest Daly firmware via their PC tool rather than just the app. The app updater has a known timeout bug that bricks the session halfway through, leaving it worse than before.

If drop-outs persist regardless of temperature, the BMS itself may just be marginal. JK BMS is worth serious consideration at similar price points.

Good shout from @VivaroWanderer on the temperature angle, but worth adding that I've seen this same drop-out behaviour on a Daly Smart in a perfectly warm environment — turned out to be ground loop noise from the MPPT interfering with the BMS UART line.

In my setup I added a small ferrite choke on the Bluetooth module's comms lead and the drop-outs stopped almost entirely. The Daly's onboard shielding is genuinely poor.

Also worth checking: Daly's app version matters a lot. The older Android builds have a known timeout bug where the app silently drops the connection but logs no error — looks identical to a hardware fault. Update to at least v2.4.1 and test again before chasing a hardware fix.

If you're on iOS, that's a separate headache — Daly's iOS BLE stack has never been reliable in my experience.

Great points from @EllaPalmer, @VivaroWanderer and @BarryWood already. One thing I'd add that hasn't been mentioned yet — check your USB-to-UART adapter if you're using one to monitor via the Daly app. The cheap CH340-based adapters are notorious for dropping connection intermittently, especially on longer cable runs. Swapping to a CP2102-based adapter sorted persistent drop-outs for me on a very similar setup.

Also worth double-checking your Bluetooth app version — the Daly Android app in particular has had some buggy releases where it loses the BMS connection seemingly randomly but the BMS itself is actually fine. If your Victron kit isn't throwing any actual protection events, the BMS may be behaving correctly and it's purely a comms/monitoring issue rather than anything fundamental. Would rule that out before digging deeper.

Good thread. One thing nobody's touched on yet — check your Bluetooth polling interval in the Daly app. By default it hammers the BMS fairly aggressively, and on the Smart BMS the UART and Bluetooth share the same comms buffer. If the MPPT is simultaneously pushing charge data through the VE.Direct chain and the app is polling hard, I've seen the BMS just silently drop the Bluetooth connection rather than throw an error.

In my garden office setup I pulled the polling interval back to 10 seconds and the random drop-outs essentially vanished. Worth ruling out before you start chasing hardware faults.

Also — are you using the official Daly app or a third-party one like overkill solar's? The third-party implementations can be considerably more aggressive with their keep-alive packets.

Good thread, this. One thing worth mentioning that I haven't seen raised yet — have you checked the quality of your BMS ground connection back to the negative busbar? I had near-identical drop-outs on a client's narrowboat install last spring, drove me mad for weeks. Turned out the BMS ground wire had a dodgy crimp that was causing intermittent resistance. Swapped it for a proper soldered and heat-shrunk connection with a decent ring terminal and it's been rock solid since. Worth checking before you go too far down the Bluetooth or polling rabbit holes that @SuffolkCruiser mentions.

Tiny house owner here — mine fixed itself the moment I stopped routing the BMS cable within six inches of the inverter's AC output wiring, which was basically acting as a noise antenna for the Bluetooth module. EMI interference is the silent killer nobody mentions until you've already tried every app setting twice.