Anyone else had grief with MPPT controllers throwing fault codes in cold weather?

Picked up a Victron SmartSolar 100/30 back in September and it's been brilliant — until last week when temperatures dropped to around -4°C overnight here in the Peak District. Woke up to find the controller showing an error 17 (temperature sensor fault) and the whole system had basically stopped charging. Two 200W panels on the roof of my shepherd's hut, 200Ah of lithium, so not a small setup to have sitting dead in the cold.

I've got the controller mounted inside the hut on an internal wall, so I wouldn't have thought ambient temperature would be the issue. Battery is a Battle Born so it's got its own BMS and low-temp cutoff, but the Victron had already stopped before the BMS would have kicked in. Done a fair bit of reading and some people reckon it's worth adding a small heat mat behind the controller, others say it's just a firmware quirk that got patched ages ago — but I'm on the latest firmware (v3.14) so I'm not sure that explanation holds.

Has anyone actually experienced this specific fault in winter, particularly with a lithium setup? Wondering whether the temperature sensor is just overly cautious or if there's something genuinely worth investigating before we get deeper into January.

@JoeFisher the -4°C overnight temp is almost certainly your culprit. What's your battery chemistry? If you're running lithium (LiFePO4), most BMS units will assert a charge-inhibit signal below 0°C to prevent plating damage — the Victron will see this as a load disconnect and throw accordingly.

On the SmartSolar specifically, check your VE.Smart network battery temperature input in the Victron Connect app. If the controller is reading an uncalibrated or absent temp sensor, it may be applying incorrect absorption voltage compensation, which can trigger protection faults.

With my Fogstar Drift 200Ah in the motorhome, I sorted this by enabling the low-temperature cutoff on the BMS and configuring the SmartSolar's charge profile to match — once both sides agreed, the fault codes disappeared entirely.

What battery type are you running?

Same thing caught me out on the narrowboat last winter. The Victron threw what looked like an alarming fault but it was actually the batteries being too cold to accept charge properly — the BMS on my Fogstar lithiums was protecting them.

Worth checking your battery temperature in the Victron app before assuming the controller itself is the issue. If you've got lithium without a heated blanket or insulation around the bank, the BMS will throttle or cut charge acceptance entirely when cells drop below around 5°C.

@JoeFisher — what battery chemistry are you running? If it's AGM you've got a bit more tolerance, but the absorption voltage will still need adjusting for cold temps. Victron's temperature compensation should handle it automatically if you've got the Smart Battery Sense dongle paired up.

IanMartin60 | Posts: 847

@JoeFisher worth checking whether it's actually the controller itself getting cold or whether it's the battery temperature protection kicking in. The SmartSolar 100/30 has a BMS temperature input and if you've got a compatible battery with a temp sensor connected, it'll throttle or halt charging below a certain threshold to protect the cells — which is exactly what it's supposed to do, not a fault as such.

Had identical confusion with mine up in the Dales two winters back. Turned out everything was working perfectly, I just hadn't read that section of the manual properly!

If you're using the VictronConnect app, pull up the history tab — it'll show you whether it was a genuine protection event. Makes diagnosing it much easier than staring at the LED blink codes in the cold at 7am! 😄

@Barry1988 interesting you mention the narrowboat — same situation here. What I've found is that the real headache isn't always the fault itself but trying to diagnose it when you're moored somewhere remote with no decent signal to pull up the VictronConnect history properly.

Have you tried setting up the low temperature cutoff in the battery settings if you're on lithium? I only recently discovered you can configure this via Bluetooth on the SmartSolar and it at least makes the shutdown deliberate rather than a confusing fault code.

@JoeFisher — can you confirm what battery chemistry you're running? That would narrow it down significantly. If it's a lead-acid setup the cold behaviour is quite different to lithium and the fix is completely different.