Anyone else struggling to keep the leisure battery topped up on short winter drives?

Really struggling with this at the moment. My 200Ah Fogstar lithium is barely seeing any meaningful charge from the alternator on my usual 20-30 minute school run errands — by the time the B2B charger has woken up and started pushing decent current, I'm already parked up again.

A few things I'm curious about from others' experience:

• Does anyone run a higher-output B2B? I've got a 30A Sterling at the moment but wondering if stepping up to a 60A would actually make a difference on short hops, or whether the limiting factor is just time rather than current
• Solar in winter — obviously not a silver bullet but does anyone find even a small roof panel helping maintain state of charge between trips? I'm in the Midlands so we're talking minimal sun hours right now
• Is anyone pre-warming their lithium BMS? Mine cuts out completely below about 3°C which isn't helping matters

The van mostly sits on the drive between weekend trips, so I'm also running a Victron IP22 mains charger overnight when I remember, but I'd rather the system be more self-sufficient.

Wondering if this is just a "wait for spring" problem or if there's actually a practical fix others have found. Anyone switched to a DC-DC charger with a larger alternator and noticed a real difference? Would be interested to know what setups people are running.

@CarolThomas79 your B2B is basically just warming up by the time you've parked — lithium's dirty little secret is it wants a long run, not a school-run.

Fit a proper solar top-up for the static days; even a modest 200W panel on the roof will do more heavy lifting through winter than 47 short drives ever will. My Victron SmartSolar on the garden office laughs at overcast skies more than I'd expect.

Alternatively, set your B2B profile to hit a lower absorption voltage so it charges faster in the window you've got — most Fogstar cells are perfectly happy at 14.2V rather than faff­ing about trying to squeeze to 14.6V on a 25-minute commute.

@CarolThomas79 welcome to the joy of British winters, where the sun disappears in October and your alternator does a 20-minute comedy warm-up act before actually doing anything useful — my Victron Orion-Tr Smart sits there looking smug in my van while I'm basically just moving electrons from one end of the car park to the other.

@CarolThomas79 mine spent three months last winter essentially acting as a very expensive paperweight until I wired in a proper shore power top-up at the house — B2B and a British winter are basically two people who've agreed to meet but keep missing each other. 🔌

Genuinely curious about something nobody's mentioned yet — what's your B2B charger rated at, @CarolThomas79? I've got a similar setup in my garden office feed from a van and found the sweet spot was massively dependent on whether the B2B could actually pull enough amps to matter in a short window.

I upgraded to a Victron Orion-Tr Smart 30A and even a 25-minute run shifted a noticeable chunk. Previously had an underpowered unit that was essentially ceremonial.

Also worth checking — is your alternator actually reaching full output before you've parked? Older diesels especially can take 10+ minutes just to settle properly, which eats into your already tight window.

What van and alternator are you running? That might narrow down whether it's the B2B spec or just the physics of winter driving working against you.

@CarolThomas79 worth bearing in mind that your B2B charger needs a decent chunk of time just to ramp up and stabilise before it's delivering meaningful current — on a 20-30 minute run you're probably only getting 10-15 minutes of actual bulk charging once everything's woken up. As @Macca97 hints, the charger rating matters, but so does your alternator's output once it's already managing engine electrics in cold weather. Have you checked what your starter battery voltage is sitting at mid-journey? If it's lower than you'd expect, the B2B will throttle back to protect it. Might be worth logging a longer run with a battery monitor to see what you're actually getting. Sometimes the numbers are more depressing than you'd imagine!