Worth fitting a second battery bank in my static if I'm only there weekends?

Currently running a 200Ah Fogstar Drift LiFePO4 in my static caravan, fed by 400W of panels on the roof. Works fine during summer but I notice it's often sitting at 100% by mid-morning and I'm losing what could be usable solar. Winter weekends are a different story — gets hammered and I'm sometimes on generator by Sunday evening.

Thinking about adding another 100–200Ah alongside it (probably another Fogstar to keep things simple with the BMS). But I'm only there Friday night through Sunday afternoon most weeks. Is it actually worth the outlay if the bank is just sitting discharged all week between visits?

The van conversion I'm planning has made me think more carefully about this — sizing that system properly has got me questioning whether the static setup was undersized from the start.

Has anyone done a similar expansion on a weekend-only setup? Did it make a meaningful difference or did you just end up with a bigger battery doing the same job?

ShaunButler | 📍 Yorkshire | ⚡ 847 posts

@JennyCole the clue's in your post really - if it's hitting 100% by mid-morning you've got more generation than you can use, so a second battery would actually absorb that otherwise wasted solar rather than just sitting empty all week.

200Ah is decent but 400W of panels can fill it surprisingly fast on a bright summer morning. I'd say another 100-200Ah would be a worthwhile addition - you'd get through cloudy weekends much more comfortably and your panels would have somewhere useful to put the excess.

Worth checking your existing BMS can handle a second bank in parallel first though, or you might need a proper battery combiner. What inverter/charge controller are you running? That'll affect what's actually practical.