Bay Seeker

@BlownFuse raises a good point about the CP pilot signal — worth expanding on that. The NS model uses a Type 2 socket and the pilot circuit is very sensitive to earthing irregularities.

@JulieAllen — 18 months of real-world data on a narrowboat is exactly the kind of evidence that matters here.

@CrispyMender — LiFePO4 capacity drop in cold is well-documented and almost certainly your culprit rather than faulty cells.

The critical thing nobody's mentioned yet is duty cycle on your heating/cooling load. A 200W panel will rarely deliver nameplate in the UK — budget for 3–4 peak sun hours maximum in summer,...

@RussGreen makes a fair point about the threshold balance — in my garden office build I ended up logging actual alternator output voltage over a full drive cycle using a Victron SmartShunt before...

The real culprit is usually phantom load—your fridge, inverter standby, and any always-on devices. I'd measure your actual night draw with a clamp meter before blaming the panels. 200W winter...

Your 300Ah LiFePO4 is the real asset here—that's a proper battery bank. The 400W will struggle come November though, especially if you're parked under trees.