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

Really struggling with this at the moment. My 100Ah AGM leisure battery barely gets above 80% state of charge through the week because the daily commute just isn't long enough to put anything meaningful back in — by the time the alternator's properly charging, I'm already parked up again.

I've been looking at whether a B2B charger (DC-DC) would help squeeze more out of those short runs. Apparently a Victron Orion-Tr Smart would be more efficient than relying on the standard split-charge relay, which just isn't cutting it in winter. Has anyone actually seen a noticeable difference switching over?

The other issue is obviously the shorter daylight hours killing solar input. I've got a single 100W panel on the roof and it's doing virtually nothing from November through to February — partly shading, partly just rubbish irradiance levels.

My current workaround is plugging into mains via a hook-up lead once a week at home, which feels like it defeats the point of having a leisure battery setup at all. I'd rather the van was doing more of the heavy lifting itself.

A few questions for anyone who's been through this:

• Is a B2B charger worth the outlay if your drives are genuinely short (under 20 minutes)?
• Would adding a second panel help, or is the irradiance issue just too limiting in winter?
• Anyone tried Fogstar lithium as a swap — does better chemistry actually help with partial charging cycles?

Curious whether this is just a winter reality everyone accepts or whether there are practical fixes that actually work without spending a fortune.

@MandyMorris not really my world (narrowboat here) but same problem in winter — engine alternator just can't keep up with what you're pulling overnight.

Honestly the fix that transformed things for me was a Victron Orion-Tr Smart DC-DC charger. Properly charges the leisure bank rather than just trickling whatever the alternator feels like chucking over. Worth every penny.

Also worth checking if your split charge relay is actually doing anything useful in cold temps — they can be pretty rubbish.

Longer term, even a small Fogstar LiFePO4 swap would help massively since lithium accepts charge so much faster during those short runs.

@MandyMorris this is exactly why I fitted a Victron Orion-Tr Smart DC-DC charger between my van alternator and leisure battery. The standard split-charge relay setup is pretty useless in winter — your alternator voltage drops and the relay barely opens properly anyway.

The Orion properly regulates the charge and you can set absorption/float voltages correctly for AGM chemistry. Even on a 20-minute run I'm seeing meaningful charge put back in now.

One thing worth checking — what's your cable run length between alternator and leisure battery? Voltage drop kills efficiency on longer runs. Also, has your AGM had any deep discharge cycles? Once they drop below ~10.5V a few times they lose usable capacity permanently, so 80% SoC might actually be your new 100%.

What's the alternator output rated at on your motorhome?

@MandyMorris been there. Short runs in winter are basically useless for charging — alternator voltage drop across a cheap split charge relay means you're barely tickling it.

What sorted mine was ditching the relay entirely and going lithium (Fogstar Drift 100Ah). The Orion-Tr @WattKaren mentioned is decent but you still need a decent bulk charging window to see real benefit.

Honestly though if you're staying AGM, a small mains charger plugged in overnight whenever you're near a socket will do more than any amount of short drives. CTEK do a good one for AGMs specifically.

Also worth checking your AGM isn't just knackered — they sulphate badly if they've been sitting low repeatedly. 80% over winter weeks adds up to damage fast.

@WattKaren already nailed the Orion-Tr recommendation so won't rehash that — but worth noting if you're in a shepherd's hut or static setup like me, a small mains trickle charger overnight solves this completely. If you're genuinely mobile though, have you looked at your split charge relay? Cheap ones basically throttle your charge before it even starts. Replaced mine with a proper voltage-sensitive relay and the difference was noticeable immediately. Also worth checking your alternator output cable gauge — undersized wiring is basically an invisible tax on every charge cycle. AGMs need that bulk charge phase to hit properly or you'll be stuck in that 75-85% purgatory all winter. Fogstar do decent AGM replacements if yours is getting on a bit too.

@MandyMorris one thing nobody's mentioned yet — check what's actually drawing from that battery overnight. Even small parasitic loads (fridge on eco mode, alarm systems, habitation control panels) can quietly drag you down 5-10% while you sleep, which compounds the problem massively when you're already struggling to charge on short runs.

Fit a simple battery monitor if you haven't already — a Victron BMV-712 or even a cheap Votronic unit will show you exactly what's leaving and when. You might find you're losing more overnight than you think, which makes the short-drive charging problem look even worse than it actually is.

Fix the drain first, then address the charge input side. Otherwise you're essentially trying to fill a leaky bucket faster rather than just plugging the hole.