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

Short winter drives are genuinely brutal for battery management. I spent last December watching my Fogstar 100Ah LiFePO4 barely nudge above 50% SOC after a 45-minute run because the alternator time just isn't there.

The core problem is that modern smart alternators throttle output aggressively — your B2B (DC-DC) charger only gets maybe 20-30 minutes of proper charging before you're parked up again. At that point solar is doing virtually nothing useful either, especially if you're in Scotland or the north of England where the sun barely clears the roofline in January.

A few things that genuinely helped in my Transit:

• Renogy 40A DC-DC charger — pushing the charge rate as hard as possible during the limited drive time
• Prioritising loads — ruthlessly cutting anything non-essential (goodbye heated blanket during the day)
• Shore power top-up where available — even a cheap site hookup or a mate's driveway 3-pin once a week makes a difference

The Victron MPPT still earns its keep on bright winter days, but I wouldn't rely on it as a primary source November through February.

What's everyone else doing? Particularly curious whether anyone's fitted a larger B2B to squeeze more out of short runs, or whether you've just accepted that winter means managing lower SOC and sizing your consumption accordingly. There must be a reasonable middle ground between a full shore power dependency and constantly anxiety-watching the BMS readout.

@XO_Sparks not a motorhome situation for me but I had the exact same headache running a Victron setup in my garden office via a van-based charging arrangement last winter.

What finally made a difference was fitting a DC-DC charger (B2B) rather than relying on a direct split charge relay. The relay just couldn't push meaningful amps in time, but the B2B actually regulates the charge properly even when the alternator isn't fully warmed up.

Worth checking whether your van has a smart alternator too — loads of modern vehicles throttle output which makes short runs even worse.

Can I ask what you're currently using to connect the leisure battery to the alternator? That seems like the critical detail here.

@XO_Sparks this is a classic B2B charger situation. A decent DC-DC unit like the Victron Orion-Tr Smart 30A will properly regulate the charge going into your LiFePO4 rather than relying on the alternator doing whatever it fancies.

The key thing most people miss — standard split-charge relays see the lithium's low internal resistance and think it's already full. The B2B solves that by actively managing current.

I ran exactly this problem in my motorhome last January doing short school-run-style hops. Fitted the Orion and even a 20-minute drive was genuinely contributing meaningful charge.

Worth checking your alternator rating before sizing the unit though — some older MoHo chassis alternators struggle if you throw a full 30A demand at them cold.

@SimonKelly is right about the B2B, but worth adding — in winter you're also fighting cold battery chemistry slowing acceptance rates, not just alternator time.

I ran into this exact wall with my motorhome last January. Even with an Orion-Tr Smart fitted, I had to manually bump the charge profile slightly for the colder months. The "smart" part only helps if you've actually dialled in the settings to match your specific cells.

Also worth checking your battery's own low-temperature cut-off. Some Fogstar packs won't accept charge below a certain threshold at all — the BMS just refuses it. You might be sitting there thinking you're charging when you're not touching the battery whatsoever.

Short drives in December are genuinely a losing battle without also having solar or a mains hookup to compensate overnight.

@RustyTinker my cabin LiFePO4 laughs at short drives too — fitted an Orion-Tr Smart and now even a 20-minute school run charges more than my kids drain my wallet.