Anyone else running a dedicated circuit for a garden office? Curious how you've sized yours

Been powering my garden office from a standalone solar setup for about 18 months now. Currently running a 400W panel into a Victron SmartSolar 100/20, feeding a 100Ah Fogstar Drift LiFePO4. Covers the basics — laptop, monitor, a couple of USB charging points, and a small LED strip — without any drama most of the year.

Winter's where it gets interesting. December and January I'm regularly seeing the battery drop below 40% SOC by mid-afternoon if it's been cloudy for a few days running. I've managed it by shifting heavier tasks to mornings, but it's not ideal when you're on back-to-back calls. Considering adding a second 100Ah battery or bumping the panel capacity to maybe 600W total.

The one thing I haven't cracked yet is supplementary heating without blowing the whole budget. A small oil-filled radiator is obviously a non-starter on 100Ah. Anyone gone down the 12V heated mat route or found a low-draw solution that actually works in a UK winter rather than just taking the edge off?

Hey @AlexPalmer60, similar setup here but I went slightly bigger after underestimating my loads initially. Running a 600W array through a Victron 100/30 into a 200Ah Fogstar Drift. The extra headroom has been brilliant through these grey winter months - those 400W panels really struggle when you're getting 2-3 hours of usable light in December.

One thing I'd suggest if you haven't already - grab a Victron Cerbo GX if your budget allows. Being able to monitor state of charge properly rather than guessing has genuinely changed how I use the office. Stopped me accidentally hammering the battery on overcast days.

What are you running loads-wise? That'll determine whether your current setup is genuinely sufficient or just about scraping by.

@AlexPalmer60 worth doing a proper load audit before assuming 100Ah is enough long-term. Same mistake I made early on with my motorhome build — looked fine on paper until I added a monitor and saw the actual draw patterns.

Key thing people overlook is vampire loads from office kit — monitors on standby, routers, laptop chargers sat idle. They add up surprisingly fast over a 24-hour period.

If you're planning to expand, check your SmartSolar 100/20 headroom first. The 20A charge limit means you're already close to saturation with 400W depending on your battery voltage — adding panels without upgrading the MPPT is a common bottleneck.

Fogstar Drift is solid for the money though. If you do eventually upsize capacity, two in parallel is straightforward with that BMS design.

Really nice setup @AlexPalmer60! One thing worth considering beyond just capacity is how you're managing your winter months - that 400W panel will take a proper hit come November through February up here in the UK. I'd think about whether your 100Ah is genuinely cycling efficiently during those shorter days or whether you're accidentally deep discharging more than you realise.

The Fogstar Drift is a solid choice mind you, it'll handle that far better than a lead-acid would. Have you got the Victron app monitoring your state of charge properly? Being able to see your actual daily consumption patterns over a few weeks makes it much easier to spot whether you need to upsize the panel array before committing to a bigger battery.

What sort of loads are you actually running in there? That'd help give more specific advice.

Great setup @AlexPalmer60! One thing worth considering beyond raw capacity is your winter performance - that 400W panel will take a real hit November through February with low sun angles and shorter days. I've got a similar office setup and added a small wind turbine as a secondary input which made a massive difference over winter when solar production drops off a cliff. Also, have you looked at your Victron app data to see what your actual daily consumption looks like across different seasons? The SmartSolar logging is brilliant for spotting patterns you'd never notice otherwise. Might find you're fine in summer but struggling more than you realise come January. What are you actually running in there - monitors, heating, the lot?

Great setup @AlexPalmer60! I'd echo what @Jonno45 and @Davo22 are getting at about winter, but wanted to add something nobody's mentioned yet - have you thought about your cable run from the panel to the controller? Voltage drop over longer distances can really eat into your harvest, especially on cloudy days when every watt counts. Worth checking your cable sizing with a voltage drop calculator if you haven't already. I've got a similar setup powering my own garden office and switching to 6mm² cable on a 12m run made a noticeable difference to my charging performance. Also, if you're running any equipment with a high inrush current like a laser printer, make sure your Victron is set up with appropriate low battery cutoff settings to protect that Fogstar battery. Lovely bit of kit that Drift though, been dead reliable for me!

Good shout from everyone on the winter side of things. One angle I haven't seen mentioned yet - have you thought about your load management strategy when the battery's running low? With a 100Ah LiFePO4 you've got decent capacity, but if you're doing video calls or running a monitor alongside everything else, those peak draws can catch you out on a grey February afternoon.

Worth setting a low voltage disconnect on your Victron at around 20% SoC rather than letting it drain further - protects the cells long term. The SmartSolar app makes this fairly straightforward to configure if you haven't already done it.

Also curious what your typical daily load looks like in kWh? Would help the thread figure out whether your setup's genuinely well-matched or whether you're getting lucky with light usage. 🙂

Really nice setup @AlexPalmer60! Jumping on what @MeadowHermit raised - worth thinking about your cable run length from the panels to the controller too. Voltage drop over longer distances can quietly rob you of efficiency, especially on gloomy winter days when every watt counts. I'd also suggest logging your actual consumption for a couple of weeks if you haven't already - most people are surprised how much a monitor, laptop charger and even standby devices add up. The Victron app makes this dead easy if you're not already using it.