Victron MPPT kept dropping connection overnight — faulty unit or just settings?

Had this exact issue on my narrowboat last winter. Turned out to be the VE.Direct Bluetooth dongle rather than the MPPT itself — the dongle was dropping its BLE connection when temps dropped overnight, not the actual charge controller.

Few things worth checking:

• VE.Direct cable seating — give it a firm reseat at both ends. Sounds obvious but caught me out
• Victron Connect app version — there was a patch a while back specifically for connection stability
• Is it actually dropping, or just showing as dropped? The app can timeout and show disconnected even when the MPPT is happily charging away

If you're seeing the unit actually stopping mid-charge (not just the app losing comms), that's a different issue. Check your battery temp sensor readings if you've got one fitted — the algorithm can throttle or halt charging if it's reading something daft.

Also worth pulling up the history data in VictronConnect. The daily logs will tell you whether it actually stopped pushing amps or just lost the wireless link. That one data point narrows it down massively.

What MPPT model is it — SmartSolar or BlueSolar? And are you connecting via Bluetooth direct or through a Cerbo/GX device? Makes a difference to where the fault likely sits.

Others had similar with Renogy kit but Victron's firmware is generally solid in my experience. Wouldn't write the unit off yet.

@CaddyProject — that rings a bell from my own narrowboat days. The dongle issue is well documented but there's another culprit nobody mentions: if you're running VictronConnect on an older Android device, the app itself will drop the connection when the phone throttles its Bluetooth radio to save battery overnight.

Worth checking whether the MPPT is actually losing connection or just the app losing sight of it. Pull the history data directly via VE.Direct cable the next morning — if the charging cycles look clean and uninterrupted, the controller was fine all along and it's purely a comms problem.

My Fogstar batteries threw up similar phantom alarms once. Turned out the phone was the culprit the whole time.

Worth adding to what @CaddyProject and @HazelDawn are getting at — before replacing anything, check whether the MPPT itself is actually dropping out or just the Bluetooth visibility. Log into VictronConnect via USB/VE.Direct cable and pull the history data. If the charging cycles look uninterrupted overnight, your hardware is fine and it's purely a comms issue.

I had similar on my van build and the fix was simply disabling the dongle's "sleep mode" in the Victron app settings — easy to miss but it's under the device info screen. Some of the older dongles also benefit from a firmware update, which you can push through VictronConnect directly. Worth trying before spending anything.

@CaddyProject had the same faff on my static last year. Before you chase the dongle rabbit hole though — check your VE.Direct cable first. Mine had a dodgy crimp that only showed up when the van cooled down overnight, connector was expanding/contracting with the temp and losing contact intermittently.

Also worth checking if it's actually dropping connection or just the app timing out. Two very different problems. Victron Connect has a known issue where it'll show "disconnected" but the MPPT is cracking on fine in the background.

Genuine fault is rarer than people think. Usually settings or a naff cable tbh.

My Fogstar-fed setup in the shepherds hut did exactly this last January — swapped the dongle, problem vanished, felt like an absolute genius for about 30 seconds until I realised I'd just bought a £30 fix for a £15 cable issue.

Classic narrowboat winter gremlin, this one. Had the exact same drama on my old 57-footer two winters back — except I spent three days convinced my Victron SmartSolar 100/30 had gone doolally before realising the dongle was basically throwing a tantrum every time the bilge temperature dropped below about 5°C.

What nobody's mentioned yet: check whether you've got Bluetooth pairing conflicts. If you're also running a BMV-712 or Cerbo GX nearby, occasionally they'll all start squabbling over the BLE handshake like siblings in the back of a Transit.

The fix that actually sorted mine was switching to a VE.Direct USB cable into a Raspberry Pi running Venus OS — rock solid ever since, no Bluetooth nonsense whatsoever. Overkill for some, but on a narrowboat you've already accepted "overkill" as a lifestyle philosophy. 🚢

Worth checking one more thing before swapping the dongle — the VE.Direct cable itself. Had this on my garden office setup last autumn, Victron SmartSolar 100/30, and the culprit was a slightly loose VE.Direct connector that was expanding/contracting with the temperature swings overnight. Reseated it properly and the phantom dropouts stopped completely.

Also — if you're using the VictronConnect app on Android, there's a known issue where aggressive battery optimisation kills the BLE connection in the background. Worth whitelisting the app in your phone's battery settings before assuming it's hardware.

@ValleyChild's dongle swap is still a solid call if the above doesn't sort it, mind. Just cheaper to rule out the easy stuff first.

Really relates to my narrowboat setup this! One thing nobody's mentioned yet — check your MPPT firmware in the VictronConnect app. Had a dodgy overnight disconnect issue on mine and a firmware update sorted it completely, no hardware swap needed. Think it was a known BLE stability bug in an older build. Worth ruling out before spending on a new dongle. Settings-wise, also double-check your Bluetooth sleep timeout — some units will deliberately drop connection after inactivity to save power.