Anyone else found their garden office battery barely lasting through a cloudy week in winter?

Same issue hit me hard last January. Running a 200Ah LiFePO4 (Fogstar Drift) and even with a 400W panel array it was genuinely touch and go by day four of solid grey skies. Ended up having to throttle back the heating and swap to a laptop instead of the desktop just to stretch it out.

Few things that actually helped me:

• Bumped up to 600W of panels — more surface area matters more than you'd think when irradiance is rubbish
• Added a small Victron SmartShunt so I could actually see what was happening in real time rather than guessing
• Grid backup via a Victron MultiPlus on a timer — just tops up overnight on the cheap rate if SOC drops below 20%

That last one felt like cheating at first but honestly it's just being practical. Garden office has to be usable, not a survival exercise.

The bigger question is probably battery sizing. Most people underestimate winter loads — heating, lighting, monitors all running longer hours. I'd say whatever you think you need, double it if you want genuine off-grid confidence through December and January.

What are others running capacity-wise? Curious whether anyone's gone down the second-battery route rather than just grid backup.

@ShortCircuit yeah, this is the reality of UK winters that the YouTube solar crowd doesn't really talk about. A 200Ah bank sounds decent until you factor in that your panels might only pull 10-20% rated output across a full grey day in December.

Few things that helped my garden office setup:

• Grid tie-in as backup — even a cheap consumer unit feed means you're not dead in the water
• Victron MPPT with load output scheduling, so non-essentials cut automatically when SOC drops below ~40%
• Oversizing panels aggressively — I'd want 600W minimum for reliable winter use with that battery size

Honestly though, without mains backup you're always gambling against British weather. A second 200Ah Fogstar in parallel would help more than extra panels at that point.

What's your actual daily load in winter? That number matters more than most people realise.

@ShortCircuit my van taught me this lesson the expensive way — 200Ah in January UK is basically a decorative ornament, I've got a second Fogstar Drift wired in parallel now and it still gets sweaty by day three of proper grey soup weather.

@ShortCircuit 200Ah for a garden office through a British winter was always going to be marginal at best. I run 400Ah of Fogstar cells with a Victron Multiplus as backup from the mains — and I still had to lean on the grid twice last February.

The bit nobody mentions is that your panels are producing maybe 15-20% of their rated output on a proper overcast January day. Do the maths before you buy, not after.

Honestly the only sensible solution for a working office is either a significantly larger bank or a grid-tie fallback. Relying purely on solar in the UK between November and February is asking for trouble. It's not a van — you presumably can't just drive somewhere sunnier.

Really interesting thread — I'm facing a version of this on my narrowboat rather than a garden office, but the principle is identical.

One thing nobody's mentioned yet: have you looked at your inverter idle consumption? I found my Victron Multiplus was chewing through a surprising amount just sitting there during those grey stretches. Enabling the dynamic cutoff and ECO mode made a noticeable difference to how long the bank lasted through low-generation periods.

Also worth checking your actual usable capacity — not all 200Ah LiFePO4 cells are created equal, and if your BMS is cutting out early you might be losing 10-15% before you even start throttling loads.

@VitoProject curious what your monitoring setup looks like — are you using a Cerbo GX to track consumption patterns over those cloudy stretches?