Complete camper van electrical system designer. Solar + alternator + shore power, per-circuit wire and fuse sizing, wiring schema, and 24-hour battery simulation.
Built for Sprinter, Transit, ProMaster, and any cargo van conversion. Pre-loaded with realistic van life appliances.
Toggle each source you'll have. Combining sources lets you safely reduce battery size.
| Appliance | Watts | Qty | Hrs/day | Wh/day |
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| Appliance | Watts | Peak W | Qty | Hrs/day | Wh/day |
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Hourly battery state-of-charge with current charging sources and loads.
Conceptual diagram showing busbars, charging sources, and circuits with cable/fuse sizing.
Each load needs its own properly-sized fuse and cable. Based on 3% voltage drop @ 4m wire length.
| Circuit | Type | Watts | Amps | Cable | Fuse |
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Most cargo vans have 60–120 sq ft of usable roof. That fits 400–800W of solar depending on panel size and roof fan/AC placement. Flexible panels fit curved roofs but lose ~5% efficiency vs rigid.
Vans have a major advantage over RVs: DC-DC alternator charging. A 30–60 minute drive can push 30–50A into your house battery. Most full-timers combine 200–400W solar + 30A DC-DC and rarely run out.
Nearly all van builds use 12V: short wire runs, plenty of 12V appliances, and a single 100–300Ah LiFePO4 covers most needs. Go 24V only if your bank exceeds 5kWh or you run heavy AC loads.
Most full-time van builds run on 200–400 W of roof solar combined with DC-DC alternator charging and 200–400 Ah of LiFePO4 storage. Weekend van campers can get away with 100–200 W. Heavy users running induction cooktop, AC, or working from the van usually install 600–800 W. The calculator above factors in alternator charging and shore power, which most van calculators ignore.
Yes — a 12V mini-split AC like the Cruise N Comfort or Velit 2000 draws 60–90 A at 12V (700–1,100 W). Running 4 hours overnight needs ~280–440 Ah of usable storage plus 400+ W of solar to recharge next day. This is achievable but represents the upper end of van system size.
Yes — a DC-DC charger (also called B2B) is essential for any van with lithium house batteries. It steps your alternator output up/down to the correct LiFePO4 charge profile and protects your alternator from overloading. Common sizes are 30–60 A; choose based on your alternator capacity (rule of thumb: B2B current ≤ 50% of alternator rating).
A standard van build uses 200–400 Ah of 12V LiFePO4. Weekenders and minimalists do well with 100–200 Ah. Builds with induction cooking, AC, or 24/7 fridge plus laptops/work setup usually go 400–600 Ah. The calculator above sizes your bank based on your actual appliances and how often you drive (alternator recharge).
A Sprinter 144″ wheelbase fits 600–800 W of flexible panels (3–4 × 200 W). ProMaster 159″ fits up to 1,000 W. Transit Mid-Roof fits 400–600 W. Add roof fan, AC, or vent placement and you usually lose 100–200 W of available area. Flexible panels are easier to install on curved roofs but degrade faster than rigid (5–7 years vs 25+).
12V is the right choice for nearly all vans — short wire runs minimize the voltage-drop benefit of 24V, and the entire RV/marine appliance ecosystem is 12V. Only consider 24V if your bank exceeds 5 kWh, you run continuous loads above 3 kW, or you want longer wire runs without thick cables.