Anyone else finding 200Ah LiFePO4 isn't actually enough for two people full-timing?

Converted a Transit last year with a 200Ah Fogstar Drift battery, 400W of solar on the roof, and a Victron SmartSolar 100/30. Thought that would be plenty based on everything I read. In summer it's fine — we rarely drop below 80% SOC. But now we're heading into proper British autumn and the panels are barely producing anything by 4pm.

Running a 12V compressor fridge (about 40Ah/day), charging two laptops, lighting, and occasional phone hotspot. That's pushing 80–100Ah a day easy, which means we're draining down to 40–50% most nights before hook-up. Not dangerous for LiFePO4 obviously, but feels uncomfortably close when we're trying to avoid campsites.

Has anyone upgraded from 200Ah to 300 or even 400Ah mid-conversion without completely rewiring everything? Wondering whether adding a second 100Ah battery in parallel is straightforward with the Victron setup, or whether I'm better off just fitting a bigger alternator and leaning harder on driving to top up.

@DownsDweller the maths usually falls apart when people forget to account for actual usable capacity versus nameplate. Your 200Ah LiFePO4 gives you roughly 180Ah usable — fine — but two people running a compressor fridge, devices, lighting, and maybe a diesel heater's control board can easily pull 80-100Ah overnight before solar's even woken up.

I run a similar setup on my shepherd's hut and had to double the bank before winter made sense. The 400W solar is actually your bigger bottleneck in low-sun months — December/January in southern England you're realistically seeing 1-2 peak sun hours, so 400-800Wh maximum on a good day.

What's your actual consumption? Victron's app will show daily totals if you've got it connected via Bluetooth. That number is more useful than any general advice.

@DownsDweller I had almost the exact same setup in my van before I repurposed the system for my garden office. Two people changes the maths completely — you're essentially doubling consumption on lighting, devices, water pump cycles, everything.

Worth actually logging your real daily draw with the Victron app before assuming you need more capacity. Sometimes it's a consumption problem rather than a storage one. A 12V compressor fridge on its own can quietly chew through 40-50Ah overnight depending on ambient temps.

That said, if you're confident the usage is genuinely high, I'd look at whether you can practically fit a second 200Ah before upgrading to a single larger bank — keeps your options flexible and Fogstar's pricing makes it less painful.

What's your winter solar yield looking like on the Victron dashboard?

@DownsDweller the other thing nobody mentions is winter derating — LiFePO4 drops usable capacity noticeably below 5°C, and charging slows dramatically at low temps. My cabin setup taught me that the hard way.

Also worth checking what's actually consuming your power with a Victron BMV shunt if you haven't already. In my tiny house build I discovered my 12V compressor fridge was pulling nearly double what the manufacturer claimed in real-world conditions.

Honestly for two people full-timing I'd say 300Ah minimum, ideally 400Ah. Fogstar do their Drift in 300Ah now — same footprint roughly. Alternatively, a second 200Ah in parallel isn't as daunting as it sounds wiring-wise if you've already got a decent cable run sorted.

@DownsDweller been through exactly this. 200Ah sounds generous until two people are actually living in it — laptops, phone charging, lighting, maybe a CPAP machine, and suddenly you're burning through it faster than solar can recover on a cloudy October day.

What sorted it for me was auditing actual consumption first. Stick a Victron BMV-712 in if you haven't already — you'll probably be shocked what's drawing what.

Second Fogstar battery in parallel is the obvious answer and relatively painless if your Victron controller can handle the extra capacity (yours can, 100/30 is fine). Went from constantly anxious about state of charge to genuinely not thinking about it.

400W solar is decent but two people full-timing really wants closer to 600W if roof space allows.

@DownsDweller Something worth checking that caught me out — have you looked at your parasitic loads? Victron kit is brilliant but the MPPT, BMV monitor, and any Cerbo if you've got one all draw continuously. Add a fridge compressor cycling overnight, maybe a diesel heater's control board, and you're easily losing 10-15Ah just keeping the system on before you've boiled a kettle.

Also, are you running both laptops simultaneously during the day? That's often the killer load people underestimate — two machines plus screens can be pulling 100W+ for eight hours.

My honest suggestion: before spending on more batteries, do a proper overnight audit with your BMV data. You might find one or two culprits rather than a fundamental capacity problem. Sometimes it's a surprisingly simple fix rather than needing to double your bank.

@DownsDweller one thing worth checking before you spend money on more batteries — have you looked at your actual consumption patterns with Victron's VRM portal? I ran a similar setup and assumed the problem was capacity, but logging revealed our inverter was idling and drawing a surprising amount overnight even with nothing "on."

Also worth auditing your 12V loads separately. Fridge compressor cycling is often the silent culprit nobody accounts for properly when planning a build.

That said, if your loads genuinely are what they are, a second 200Ah in parallel is a fairly clean solution with your existing SmartSolar — the 30A charge current will be a bit leisurely filling 400Ah though, so might be worth factoring in a charger upgrade alongside it.