Before ordering cables & fuses: final technical review of 24V Victron campervan schematic

Good timing on this thread — I went through exactly this process before finalising my cable order and nearly made a couple of costly mistakes.

The thing that catches people out most on 24V Victron systems is cable sizing for the inverter/charger feed. Even though 24V halves the current compared to 12V for the same power output, folk still underestimate the voltage drop over longer runs in a Crafter-sized van. I'd strongly recommend running the Victron cable sizing tool and cross-referencing with the actual continuous draw of your MultiPlus, not just the peak rating.

A few things worth double-checking before anyone places their Fogstar or cable order:

• Fuse placement — fuse as close to the battery terminals as physically possible, ideally within 300mm. I've seen schematics where the ANL or MIDI fuse ends up halfway down the run.
• Busbars vs daisy-chaining — on a 24V LiFePO4 system with multiple loads, a proper busbar setup is far cleaner and safer than looping cables
• MCCB or fused isolator on the shore power input — easy to overlook if you're focused on the DC side
• VE.Bus cable routing — keep it away from DC cables to avoid interference with the BMS comms

If you're using Victron NG Lithium (which handles its own BMS internally), make sure your DVCC settings in VenusOS are configured correctly before you commission — it affects how the MultiPlus interacts with the battery.

Would be good to see the actual schematic posted here. Happy to give it a look alongside others on this forum — more eyes catch more issues.

Great thread @QJ_Builds — looking forward to seeing what caught you out, as I'm mid-planning on a similar build myself.

One thing I'd flag before anyone finalises their cable sizing: don't forget to account for voltage drop across your full cable runs, not just fuse ratings. On 24V systems people sometimes get complacent because the lower current compared to 12V makes everything feel more forgiving — but if you've got long runs to a bow thruster or a secondary distribution board tucked at the back of the van, it absolutely adds up.

I ran my calculations through the Victron cable sizing tool and double-checked with a separate voltage drop calculator just to be safe. Belt and braces approach, but saved me from undersizing my main battery-to-inverter run.

What specific section of the schematic are you reviewing first?

@QJ_Builds curious what your mistakes were — I'll share mine whilst waiting.

On my static caravan 24V setup, the two things that nearly bit me were:

1. Cable sizing at the inverter — people calculate for average draw but forget the surge current on startup. My Victron Multiplus pulls nearly 2x rated current for a few cycles. Undersized cable there is a fire risk, not just an efficiency issue.

2. Fuse placement — the fuse protects the cable, not the device. Anything over 300mm from the battery positive needs a fuse rated to the cable's capacity, full stop.

Also worth double-checking your busbar ratings if you're consolidating multiple loads. Cheap busbars are often wildly over-rated on the label.

@CotswoldBoater — what inverter size are you planning? That'll likely drive your biggest cable decisions.

@QJ_Builds — tale as old as time with 24V builds. My motorhome conversion taught me that most people undersize cables by calculating at 12V loads and forgetting to halve the current at 24V, then overcorrect on fusing because they're nervous.

The real trap I walked into was placing my Victron SmartShunt too far from the negative busbar — ended up with a section of unfused negative cable that technically shouldn't exist. Subtle thing but an inspector flagged it immediately.

Worth sharing your full schematic if you haven't already. Fresh eyes catch things you've stared past for weeks. I used the Victron wiring unlimited PDF as a checklist before my final cable order from Fogstar — genuinely saved me from a wrong ANL fuse rating on my multiplus feed.

Right, I'll chip in while we wait for @QJ_Builds to finish that sentence.

On my narrowboat I made the classic error of calculating cable sizing based on rated current alone and ignoring the voltage drop over longer runs. At 24V you've got more headroom than 12V, but my battery-to-inverter run was nearly 3 metres and I still had to go up a cable size to keep drop under 3%.

Anyone using Victron's own cable sizing recommendations — are they actually conservative enough in practice, or do you end up upsizing anyway?

Also curious whether people are fusing at the battery with a ANL or going MRBF. My last build I used MRBF blocks and they're neater but I've heard the ratings can be fussier. Is that just forum mythology or does it actually matter?