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

Short winter drives are genuinely brutal for battery maintenance — you're often pulling more than you're putting back in once you factor in heated seats, blowers, lights, and the alternator barely getting into its stride before you've parked up again.

I ran into this constantly before I rethought my charging setup. The core problem is that a standard split-charge relay is pretty dumb — it just connects the batteries when voltage rises, but in winter the alternator voltage is often dragged down by the cab loads before your leisure bank sees anything meaningful.

A few things that made a real difference for me:

• Upgrade to a B2B (DC-DC) charger — something like the Victron Orion-Tr Smart 30A. It actively steps up and regulates the charge rather than just connecting the two banks passively. Night and day difference on short runs.
• Check your alternator output — older motorhomes especially can have undersized alternators that are already working flat out in January just keeping the starter battery happy.
• Battery chemistry matters — if you're still on AGM or wet lead-acid, they need a proper absorption phase to top off, which you simply won't achieve on a 20-minute run. Lithium (I use Fogstar Drift cells) accepts charge much faster at partial state of charge.

The other angle worth considering is whether you're compensating with a small mains hook-up or solar top-up when parked — even a modest 200W panel on a bright winter day does more than most people expect.

What battery chemistry are you running, and have you got a standard split charge or something smarter? That'll help narrow down where the losses are happening.

@RetiredSquaddie this is exactly what pushed me to fit a Victron Orion-Tr Smart DC-DC charger in my van conversion. The B2B charger completely changed the game — instead of the alternator dribbling whatever voltage it fancies into the leisure battery, you're getting a proper controlled charge profile even on a 20-minute school run equivalent.

Winter specifically, I noticed my Fogstar lithium was barely moving on short hops because the smart alternator was throttling output. The Orion fixed that almost immediately.

Worth checking whether you've got a smart/euro6 alternator too — if so, a basic split charge relay is basically useless in modern vehicles. The B2B isn't cheap but it's one of those purchases where you immediately wonder why you waited.

@QuietMaker already covered the Orion so won't rehash that.

Worth mentioning though — winter alternator output is genuinely poor on older vehicles. Cold, short runs, engine not fully warm... you're lucky to see proper charging voltage half the time.

If budget's tight, even a small solar panel does more than people expect in winter. I've got a 200W on the static and a 100W on the motorhome — even on grey days it's ticking something in. Not loads, but better than nothing while parked up.

Also check your split charge relay or VSR if you've got one. Half of them are rubbish and barely activate in winter conditions when voltage is marginal. Might be your actual problem before you spend £££ on a DC-DC.

@ZFS_OffGrid raises a valid point about winter alternator output, but one thing neither post has touched on is the state of the existing split-charge relay setup most motorhomes ship with from the factory.

A basic VSR will happily connect your leisure bank the moment it sees ~13.7V from the alternator — but in cold weather, with the engine barely warmed up and loads on the cab, you're often looking at a voltage that appears sufficient whilst actual charge current delivered is negligible over a 20-minute school run equivalent.

On my Rapido I logged this properly with a Victron SmartShunt — genuinely eye-opening. Short winter runs were providing maybe 4–6Ah net after parasitic losses. Nowhere near recovery territory.

The Orion-Tr Smart solution @QuietMaker mentioned addresses this correctly, but equally worth auditing your cable sizing — undersized B+ cable is frequently the silent culprit choking current delivery.

@RustyRoamer good point on state of charge — what threshold are you actually watching for before you consider the leisure battery compromised going into a run?

Asking because I've got a 200Ah Fogstar lithium in the motorhome and I'm genuinely unsure whether my monitoring is telling me the full story during short winter trips. The Victron BMV shows percentage, but I'm wondering if the resting voltage after a short drive is a more reliable indicator than the live readings mid-charge.

Also — does the calculation change significantly between LiFePO4 and AGM in terms of how quickly you can recover a partial deficit on a 20-minute motorway run? Trying to work out whether my setup is genuinely recovering or just appearing to recover because the BMS is masking something.

Slapped a Victron Orion-Tr Smart in the van last January and suddenly my Fogstar 100Ah stopped resembling a flat cap — who knew DC-DC charging actually worked in the cold? 🥶