Anyone else find 12V vs 24V decisions genuinely confusing when starting out?

I've been piecing together a system for my Transit camper conversion and I keep going back and forth on whether to go 12V or 24V for the main battery bank. I've got two 200Ah LiFePO4 batteries sitting in my garage waiting to be wired up, and I originally planned to run them in parallel at 12V. But then I started reading about efficiency gains at 24V and now I'm second-guessing everything.

The main loads I'm planning for are a 40L compressor fridge (around 45W), LED lighting throughout, a 240V inverter for the occasional laptop and coffee grinder, and possibly a diesel heater controller. The inverter I've already bought is a Victron 12/1200 so I'm already a bit committed there, but I could return it if 24V genuinely makes a meaningful difference at this scale.

Has anyone actually done a proper comparison or switched from one to the other mid-build? I keep seeing people say 24V is "better" but struggling to find anyone who's run the actual numbers on a modest van system like this rather than a big static off-grid setup.

@DevonCamper the two batteries you've already got is actually the deciding factor honestly. What are they — same brand, same spec? If they're identical you can wire them in parallel for 12V 400Ah, which keeps things simple for a van build where most 12V accessories (lighting, compressor fridge, USB outlets) just plug straight in.

I went 24V on my T6 and immediately regretted how awkward cheap accessories become — everything needs a DC-DC converter or it's a faff.

24V makes more sense when you're running serious inverter loads or have really long cable runs. For a Transit camper with a Fogstar or Victron setup, 12V is generally the path of least resistance unless you're specifically planning a high-draw inverter like a 3kW+ unit.

What's your planned inverter size?

@DevonCamper I spent ages agonising over exactly this when I was setting up my shepherd's hut system. Honestly the voltage decision becomes much clearer once you look at your longest cable runs and your biggest loads.

For the hut I went 24V purely because the inverter was sitting about 4 metres from the battery bank — at 12V the cable gauge needed to handle that current was getting ridiculous and expensive. Victron's own guidance nudged me that way too.

For a Transit though, everything's relatively compact. If those two batteries @T6Project mentioned are identical spec, wiring them in series for 24V gives you headroom for an EV charging setup later without melting cables — which is exactly where I wish I'd planned ahead on my own install.

What inverter size are you targeting? That'll probably settle it faster than anything else.

@DevonCamper 12V if your appliances are already 12V, 24V if your inverter is massive and your cable runs are longer than a Monday morning — basically let the load make the decision for you before the batteries do.

@DevonCamper one thing worth adding that nobody's mentioned yet — think about your solar charge controller situation too. If you're planning to expand your panels later, a 24V system gives you more headroom with MPPT controllers before you start hitting voltage limits on the input side. That said, for a Transit van specifically, most of your loads are probably going to be 12V native (lighting, USB, compressor fridge etc.), so you'd be running a DC-DC converter constantly on a 24V setup anyway. That overhead adds up. With two 200Ah batteries already in hand, wiring them in parallel and keeping it simple at 12V honestly sounds like the path of least resistance for a camper build.

@DevonCamper two 200Ah batteries is actually the perfect fork-in-the-road moment — wire them in series and you've got 24V/200Ah, parallel gives you 12V/400Ah.

When I was fitting out my Kangoo (yes, tiny battery bank, hence the name...) I nearly went 24V purely because Victron's 24V inverter-chargers are noticeably cheaper per watt at that voltage.

The thing that actually made my mind up? Every single 12V appliance I'd already impulse-bought. Compressor fridge, diesel heater controller, USB hubs — all 12V native. Adding a DC-DC converter to run them from 24V felt like admitting defeat whilst also spending more money.

So honestly: inventory your existing kit first. If you're starting completely fresh, 24V is probably the smarter long-term choice. If you've already got a drawer full of 12V bits, save yourself the headache. 😄

@DevonCamper boat life forced me into this decision pretty early on — marine stuff is overwhelmingly 12V so switching everything over felt like a nightmare, which kept me at 12V even with longer runs.

One thing worth considering: what's your alternator setup? If you're charging from the van's alternator regularly, 12V is far simpler — no DC-DC converter faff, just a proper B2B charger like a Victron Orion. Going 24V means an extra layer of complexity there that caught me off guard when I was researching a similar setup.

Hey @DevonCamper, one thing I'd consider with a Transit specifically is your alternator charging setup. Most van builds rely heavily on a B2B (battery-to-battery) charger, and the 12V options are far more plentiful and cheaper than 24V equivalents. If you ever want to run a compressor fridge directly off 12V too, that's another point in favour of keeping things simple. 24V genuinely shines when you're pushing serious wattage through long cable runs, but for a camper van that's typically not the deciding factor. What's your main high-draw appliance going to be?

@DevonCamper one practical thing that'll help settle this — list every 12V load you're planning to run directly (compressor fridge, lighting, water pump etc.) and add up the current draw. If you're regularly pulling 60-80A+ through your main positive cable, you'll feel that in voltage drop and cable sizing costs. I ran 12V on my narrowboat initially and retrofitting heavier cable in tight conduit runs was genuinely miserable. 24V halves those currents, which means thinner cable and less heat. If your inverter is 2000W+, the argument for 24V gets even stronger — a 2000W 12V inverter pulls ~170A peak from your batteries, which demands serious busbars and fusing.

@DevonCamper with two 200Ah batteries you can series them for 24V or parallel for 12V — both totally valid. For a camper I'd probably stick 12V honestly. Your existing 12V accessories just work, alternator integration is simpler, and most budget inverters/chargers are 12V anyway.

24V starts making more sense once you're pushing serious wattage (think 3kW+ inverters) or running long cable runs where voltage drop matters. My garden office setup is 24V but that's because I've got a big Victron Multiplus and wanted efficiency gains. Camper loads are usually modest enough that 12V keeps life simple.