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

Mine's a Victron SmartSolar 100/30 and it's been playing up since the temperatures dropped here in South Wales. Woke up a few mornings this week to find it sat in a fault state with the absorption light flashing — had to go out and reset it manually each time. Panels are two 200W units wired in series, so around 45V open circuit in the cold which should be well within spec.

Did a bit of digging and I'm wondering if it might be related to the battery temperature sensor. I've got a 100Ah lithium (a Fogstar Drift 12V) and the BMS has been cutting out overnight when it gets below about 3°C in the garage — which then presumably confuses the Victron when it tries to wake up in the morning and sees no load acceptance. That's my best guess anyway.

Has anyone else seen this sort of thing with Victron and lithium in cold weather? I've got the VictronConnect app and can pull logs but I'm not entirely sure what I'm looking for. Wondering if I need to add the Victron temperature sensor dongle or whether there's a setting in the MPPT I should be tweaking. Any pointers would be dead helpful.

LiFePO4_King | 847 posts | ⚡ Verified Contributor

@DazHughes Sounds like it could be a low temperature cutoff situation if you're running LiFePO4 batteries. Below around 5°C the BMS should be blocking charge anyway to protect the cells, and Victron's kit is clever enough to detect that and throw a fault rather than force current in. Totally normal behaviour if that's your setup.

If you're on lead-acid, worth checking your battery cable connections — cold weather contracts the metal and loose terminals can cause voltage sensing issues that confuse the controller.

What battery chemistry are you running and what's the actual fault code showing? You can check the full history in the VictronConnect app which'll give you a much clearer picture of what's happening and at what temperature it's triggering. Usually tells you everything you need.

@DazHughes yeah had something similar with my SmartSolar last winter at the cabin. Turned out the battery temp sensor was reading way off because the sensor itself had come slightly loose from the terminal. Controller was seeing daft temperature data and throwing a wobbly.

Worth checking a few things:

• Is your temp sensor (if you have one) actually making good contact?
• Check the VE.Direct or Bluetooth app — the exact fault code will tell you a lot
• Cold batteries have higher internal resistance so absorption can behave strangely anyway

Also worth making sure your battery preset is correct for cold weather charging — Victron's adaptive absorption helps but if you're on a custom profile it might need tweaking.

What batteries are you running? AGM vs lithium makes a big difference here.

OhmsLaw | 1,203 posts | 🔧 Regular

@DazHughes South Wales winters are brutal enough to catch people out, aye. Had the exact same drama with my static van setup two winters back — Victron throwing a wobbly every morning until I worked out the panel temperature was the culprit, not the batteries.

Here's the bit nobody mentions: if your panels are rimed with frost at dawn, the Voc spikes significantly in the cold. On a 100/30 you want to double-check your array's cold-weather Voc isn't nudging past that 100V input limit. Caught me right out.

Download VictronConnect, pull the fault history properly — it'll tell you exactly which protection triggered rather than you guessing blind.

Ben1960 | 312 posts

@DazHughes One thing worth checking that nobody's mentioned yet - have a look at your VE.Connect app and pull up the history tab. The fault codes are logged there with timestamps, so you can see exactly what triggered it rather than guessing. If it's showing a #38 error that points to excessive input voltage, which can happen on very cold clear mornings when panel Voc shoots up. Cold panels produce higher voltage than the spec sheet suggests at STC, and if you're already close to your controller's 100V input limit it can push you over. Might be worth double-checking your actual panel Voc figures against last night's temperatures. Not saying that's definitely it, but it's caught a few people out and it's dead easy to rule out before pulling everything apart.