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

Had this exact faff with my SmartSolar 100/30 last winter — turned out the Bluetooth was essentially having a little kip whenever the battery voltage dropped too low overnight, which apparently is "by design" according to Victron's documentation if you squint at it hard enough.

Few things worth checking:

• VE.Direct cable instead of relying on Bluetooth — game changer for reliable logging, no more phantom disconnections
• Check your DVCC settings in VictronConnect, sometimes they get a bit argumentative with each other
• Make sure the controller itself isn't going into low-power mode — there's a setting buried somewhere that a lot of people miss on first setup

The Bluetooth dropout specifically tends to happen when the unit decides the battery is "resting" and throttles everything back. My Fogstar lithium setup sorted most of this because the voltage stays much more stable overnight compared to the old AGMs I was running, which would sag enough to trigger all sorts of dramatic behaviour from the Victron.

If you're monitoring via Cerbo GX rather than direct Bluetooth you'll probably find it's a lot more reliable — the dedicated data connection doesn't throw a wobbler the same way.

What firmware version are you on? There were a couple of updates last year that apparently addressed some of the sleep/wake nonsense, though Victron's changelog reads like it was written by someone actively trying to obscure information.

Anyone else found a fix for this that isn't just "buy a Cerbo"? Asking for my electricity bill.

@SolarKeith Classic Victron "feature" — the MPPT's Bluetooth module draws from the battery and below roughly 10.5V (12V system) it basically tucks itself in for the night.

Worth checking:

• VictronConnect → Settings → Bluetooth — some firmware versions let you set a minimum voltage cutoff for BT
• Update to latest firmware; Victron quietly fixed some sleep threshold behaviour around v1.59+
• If your battery is genuinely tanking that low overnight, that's the real problem — a Fogstar Drift LiFePO4 with a proper BMS won't let voltage sag that catastrophically

The Bluetooth dropping is honestly just the symptom waving a flag at you about your state of charge management. My 200Ah Fogstar setup paired with a SmartSolar 150/35 hasn't dropped connection once since I stopped abusing my batteries with 50%+ DoD regularly.

@OldSailor that 10.5V threshold caught me out badly first winter on the narrowboat. What nobody tells you is that the MPPT is actually fine — it's sitting there patiently waiting for dawn — but the Victron Connect app throws a wobbly and you assume something's catastrophically wrong at 0200.

My fix was embarrassingly simple: I added a Fogstar Drift 100Ah to the bank, which meant voltage never sagged that low overnight even running the inverter for a couple of hours. The dropouts completely vanished.

Worth also checking your battery cable connections before throwing hardware at it though — I had a dodgy terminal causing phantom voltage sags that looked identical to genuine low-battery disconnects. Took me three weeks of forum rabbit holes to realise it was a loose crimp all along.

@SolarKeith @OldSailor this is really useful — I've been scratching my head over almost exactly this with my motorhome setup. Quick question though: does the MPPT log data during the dropout period, or does it essentially create a gap in your VictronConnect history? Trying to work out if I'd be able to diagnose why the voltage dipped that low in the first place, or whether the evidence just disappears.

Also, does fitting a Bluetooth dongle on a VE.Direct cable change anything here, or is it drawing from the same source regardless?

@SolarKeith mine did this for three weeks before I realised I was essentially paying Victron to give me a mystery every morning — turns out a VE.Direct to USB cable bypasses the Bluetooth drama entirely and the connection never drops, because it's not relying on the unit having enough juice to shout wirelessly into the void.

Great thread, this. @SolarKeith @AnneButler — three weeks of head-scratching sounds about right, it's the sort of thing that makes you question everything except the obvious culprit.

One thing worth adding that I haven't seen mentioned: if you're running VictronConnect via Bluetooth and the MPPT is doing this, check your network key settings. I had a period where mine was "connecting" according to the app but not actually syncing properly — looked like a dropout but was actually an authentication hiccup after a firmware update.

Also worth enabling the history data in VictronConnect before bed. Even if Bluetooth drops, the controller logs overnight data locally, so next morning you can see exactly what voltage triggered the disconnect. Took me embarrassingly long to realise that was there. Saved a lot of guesswork.