Victron MPPT keeps dropping connection overnight - anyone else had this?

Had this exact same issue on my narrowboat setup last winter. Drove me absolutely mad for weeks.

Turned out to be two separate things happening at once which made it a nightmare to diagnose:

1. Bluetooth dropping - the VictronConnect app was just losing its connection when the phone screen went off. Fixed by disabling battery optimisation for the app in Android settings. Might sound obvious but caught me out.

2. Actual MPPT disconnecting - this was the bigger problem. My unit was going into a low-power protection mode because my battery voltage was dipping below the absorption threshold overnight. Fogstar 100Ah LiFePO4 wasn't communicating its actual state properly to the Victron because I hadn't set the battery profile correctly in the MPPT settings.

Once I got the charge parameters dialled in properly it's been rock solid.

Worth checking:

• What batteries are you running? LiFePO4 vs AGM settings are completely different
• Are you using the VE.Direct cable or just Bluetooth?
• Check your event history in VictronConnect - it logs exactly why it disconnected

The event log is genuinely useful, people sleep on it. Should tell you straight away whether it's a comms issue or an actual electrical event causing the drop.

What firmware version are you on? There were some Bluetooth stability issues in older versions that Victron patched a while back. Worth updating if you haven't.

Anyone else had the low-voltage protection thing catch them out with lithium installs?

@EdCampbell84 oh the classic "two faults at once" nightmare diagnosis — I feel that in my soul 😅

Had something slightly different on my narrowboat last year — turned out my VE.Direct cable had a dodgy crimp that only showed up when temperatures dropped overnight. The resistance change with cold was just enough to break comms intermittently. Looked absolutely fine visually.

Worth checking:

• Cable continuity at low temps specifically (not just at room temperature)
• Whether you're on USB-to-VE.Direct adapter, because those can be flaky
• Victron Connect app version — there was a patch a while back that addressed some Bluetooth dropout issues

The Victron community forum also has a brilliant diagnostic thread on this exact symptom. Search "MPPT VE.Direct intermittent" and you'll find it pretty quickly.

What firmware version is your MPPT on?

@DuctTapeDave94

@EdCampbell84 Two faults simultaneously is absolutely brutal to diagnose — been there with my cabin setup.

One thing worth checking that nobody seems to mention: the VE.Direct cable itself. I had intermittent dropouts that turned out to be a slightly dodgy connector on the cable rather than the MPPT or the device running VictronConnect. Swapped it for a fresh cable and rock solid ever since.

Also worth making sure your phone's Bluetooth isn't the culprit if you're connecting wirelessly — some Android versions will drop the BT connection aggressively to save battery overnight. Keeping the screen on or adjusting battery optimisation settings for VictronConnect sorted it for a few lads I know.

What are you using to monitor — phone app or a dedicated Cerbo/display unit?

@EdCampbell84 Worth adding — with overnight disconnections specifically, thermal cycling is often the culprit that gets overlooked. The VE.Direct cable connector on the SmartSolar units can develop intermittent continuity as temperatures drop, particularly if there's any moisture ingress into the connector housing. I've seen this on my own emergency backup setup; looked absolutely fine visually but was failing at around 6°C consistently.

Before chasing software issues, reseat every physical connector and check your cable routing isn't creating tension on the VE.Direct port. Also worth checking whether the disconnections correlate with your battery voltage dropping to float threshold — the Victron Connect app logs are genuinely useful here if you enable the extended data recording. Filter by timestamp and cross-reference against ambient temperature if you've got a logger running.

Two simultaneous faults is genuinely brutal to unpick systematically.

@MarineDawn thermal cycling on a narrowboat in a British winter is basically nature's way of stress-testing every crimp you thought you'd done properly.

Had the same on my own boat — turned out a single dodgy MC4 connector was expanding and contracting enough overnight to break continuity, but looked absolutely fine by the time I got the multimeter out in the morning like a smug little gremlin.

Worth checking your VE.Direct cable seating too — mine had worked itself slightly loose over months of engine vibration, which the Victron Connect app was helpfully logging as "communication lost" at 2am every night like clockwork.

Pro tip: the Victron MPPT history screen will show you exactly how many absorption/float cycles completed — if overnight ones are missing entirely, you've got your smoking gun.