Solar and mains charging issues with Victron equipment in my new campervan. Please help

Had something similar crop up with my shepherd's hut setup a while back, so this rings a few bells.

The classic culprit when solar charges fine but mains charging plays up is the charge profile settings not being configured correctly for lithium. Victron gear ships with AGM profiles by default in a lot of cases — if nobody's gone in via VictronConnect and manually set the absorption/float voltages for your specific battery chemistry, the MPPT and the mains charger (MultiPlus, presumably?) could be working against each other or simply under-charging.

A few questions that'd help narrow it down:

• What's the actual battery — is it a named brand with a BMS, or something like a Fogstar Drift or similar drop-in?
• Are the solar controller and the mains charger both connected to a VE.Bus or VE.Network? If they're not networked together, they won't coordinate charging states
• Have you enabled DVCC in Venus OS if you've got a Cerbo GX or similar?

The DVCC point is a big one that catches people out. Without it enabled, your MPPT and MultiPlus essentially do their own thing independently, which can cause all sorts of odd behaviour with lithium packs that have a BMS talking back.

Worth downloading VictronConnect and posting screenshots of your charge settings — someone here will spot it quickly. The Victron community forum is also decent for this if you want manufacturer-level input, but honestly the collective knowledge on here is just as good.

What does the battery BMS actually report during a mains charge cycle? That'd tell us a lot.

Hey @WattCharlie, good shout on the charge profile — that's definitely worth checking first.

One thing I'd add that catches people out specifically with Victron kit: make sure your MultiPlus or Quattro input current limit is set correctly in VE.Configure. If it's been left too low (sometimes defaults to 16A or even lower), the unit will throttle the mains charging significantly or behave erratically, especially on a site with slightly weak supply.

Also worth checking whether you've got PowerAssist accidentally enabled — that can cause some confusing behaviour that looks like a charging fault but isn't really.

If you're using a SmartSolar MPPT alongside a MultiPlus, double-check they're both on the same VE.Smart network or VE.Bus so they're talking to each other properly. Conflicting charge parameters between the two units is a surprisingly common gremlin. 🔧

Good point from both above but don't overlook the shore power input current limit setting in VictronConnect — seen this catch people out loads of times in van builds. If it's set too low (sometimes defaults to like 6A or even less), the Multiplus will barely pull anything from the hookup and it looks like a fault when it's just throttled right back.

Also worth checking which assistant is loaded on the Multiplus. Had a weird one in my motorhome where the ESS assistant was conflicting with normal inverter/charger operation — completely wrong for a van setup, should've had the standard generator assistant or nothing.

What Multiplus model are you running and what's your battery — lithium or lead? Makes a difference to where I'd point you next.

Has anyone actually asked what the inverter/charger model is yet? Because the troubleshooting path is pretty different depending on whether we're talking a MultiPlus, a Phoenix, or something else entirely.

Also — is the mains charging failing completely or just underperforming? Big difference there.

I've had weird behaviour in my static caravan setup where the grid input voltage was slightly low (under 207V at peak demand times) and the Victron was quietly rejecting it without throwing any obvious alarms. Worth checking the actual incoming voltage with a multimeter rather than assuming it's fine.

@PanelNige's point on the shore power current limit is solid too — what's it currently set to?

@SmartSolarNerd makes a fair point — also worth checking whether the AC input assistant is actually enabled in the VEConfigure settings, because I've watched grown adults spend three days chasing a "fault" that was just an unchecked tick box.

Wired up enough Multiplus units in my time to know Victron's defaults aren't always what you'd expect out the box.