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

Short drives in winter are basically useless for charging. Your alternator's doing well to put 10-15 amps into a depleted battery at 14v, and by the time you've done a 20 minute run to the shops you've barely tickled it.

Couple of things that actually helped in my setup:

• B2B charger (battery-to-battery) — Victron make decent ones. Forces a proper charge profile instead of whatever rubbish the vehicle's ECU decides is appropriate that day
• Bigger cable runs — most factory wiring to the leisure battery is criminally undersized. Resistance kills your charge rate before it even gets there

The other problem nobody talks about is modern smart alternators. If your van's post-2015ish, the alternator voltage is all over the place. It'll see a "full" starter battery and throttle back. A B2B sorts this too.

Solar's obviously the proper answer but December in the UK is a joke — my 200w panel on the cabin roof barely generates enough to run the voltage display showing how little it's generating.

What battery chemistry are you running? LiFePO4 accepts charge much faster than AGM so if you're still on lead-acid that's part of your problem right there. Fogstar do decent value lithium if budget's tight.

What's your current setup? Alternator output, cable size, battery capacity? Impossible to give useful advice without knowing what you're actually working with.

@GrumpyBuilder yeah the short run problem is real. Worth looking at a DC-DC charger (B2B) if you haven't already — Victron Orion-TR Smart is the go-to. Proper 3-stage charging rather than just whatever the alternator dumps in. Makes a 20 min run actually count.

That said my setup's a garden office not a van, so I'm running solar year-round instead. Winter sun is grim but even 50w on a dull day beats nothing. Might be worth a small panel on the roof to supplement?

The other option nobody mentions — just plug in when you're home if you've got a hook-up point. A basic CTEK will do more overnight than a dozen short trips ever will.

@MarkAllen69 is right on the B2B, but worth clarifying why it makes such a difference on short runs — a conventional split-charge relay just parallels the batteries, so your depleted leisure bank drags the voltage down and the alternator never gets into proper bulk charge territory. A Victron Orion-Tr Smart in isolated mode will actually profile the charge properly and squeeze meaningful amps in even during a 15-minute run.

On my narrowboat I run the Orion 30A unit feeding a 200Ah Fogstar Drift LiFePO4 bank, and even a short engine run delivers a genuine bulk charge rather than a trickle. The engine-hours-to-Ah ratio improved dramatically compared to the old relay setup.

Also worth checking your alternator's actual output voltage under load in cold weather — some modern smart alternators drop to 12.8V when the ECU decides the battery is "full," which defeats everything regardless of charger topology.

Also worth remembering your alternator's working hardest keeping the starter battery happy first, so your leisure battery's basically sat at the back hoping for scraps like a neglected Labrador.

@DefenderAdventure makes a good point about the B2B. One thing I'd add — battery chemistry matters a lot here too. If you're still on AGM or wet lead-acid, you're fighting a losing battle on short runs because acceptance rate drops off sharply once it's past ~80% charge.

Swapped my boat setup to lithium (Fogstar Drift 100Ah) and the B2B actually has something worth feeding into — lithium will happily gulp amps right up to near full.

Short winter drives went from pointless to actually useful overnight.

If you're not ready to go lithium, at minimum make sure your B2B is sized properly — a 30A unit on a big AGM bank is just tickling it.