In two years of publishing this site and running our community, we've reviewed hundreds of electrical setups posted by new builders. The same nine mistakes show up over and over. Every one of them is avoidable. Some are annoying. Two of them can cause fires.
⚠️ Electrical Safety Note
Van electrical fires are real and devastating. Mistakes #1, #2, and #3 below are fire risks. Please read them carefully and verify your existing wiring if you have any doubts.
01
No Fuse Within 18" of the Positive Battery Terminal
❌ What people do: Run a wire from the battery to a bus bar or inverter without a fuse at the battery end, thinking the fuse at the device end is sufficient.
✓ What to do: Install a properly sized fuse or Class T fuse holder within 18 inches of every positive battery terminal. This protects the entire length of that cable from the battery. If that wire shorts anywhere along its run, the fuse blows before the wire melts. Without it, you get a wire that becomes a heating element until something catches fire.
02
Undersized Wire on High-Current Runs
❌ What people do: Run 10 AWG wire from the battery to a 2000W inverter to save money. The inverter draws 160+ amps. 10 AWG is rated for 30 amps. This wire becomes a heater.
✓ What to do: Size your main cables (battery to inverter, battery to bus bar) based on the actual amperage at the load. A 2000W inverter needs 2/0 AWG at minimum. Use the Blue Sea Systems wire sizing calculator (available free on their website) — it accounts for temperature, length, and voltage drop. When in doubt, go one gauge heavier.
03
Twisted Wire Connections Instead of Crimped Lugs
❌ What people do: Twist two wires together and wrap in electrical tape. This works at first. Over time with vibration, the connection loosens, arcs, and creates heat at the joint.
✓ What to do: Crimp all connections. Use a proper ratcheting crimper (not the hardware store plier style). For large battery cables, use a hydraulic crimper or take your lugs to a battery shop that will crimp them for you. Solder and heat-shrink your smaller gauge connections. No twisted bare wire connections anywhere.
04
PWM Charge Controller Instead of MPPT
❌ What people do: Buy a PWM controller to save $40–$80 on a 400W system. Over a year in a typical climate, this wastes 200–350kWh of potential solar energy — energy that would otherwise be free.
✓ What to do: Use MPPT for any system over 200W. MPPT controllers are 25–30% more efficient in real-world conditions. The Victron SmartSolar 100/30 ($168) is our standard recommendation. It pays for the price difference in recovered energy within the first season.
05
No Battery Monitor
❌ What people do: Use the voltage readout on the charge controller or inverter to estimate state of charge. Voltage is a terrible indicator of actual battery capacity, especially on lithium.
✓ What to do: Install a proper battery monitor with a shunt (measures actual current in and out). The Victron BMV-712 ($108) is the gold standard. It shows accurate state of charge, power in/out, time remaining, historical data. You'll use it every single day. Budget for it from the start.
06
Running 12V and 120V Wires Together
❌ What people do: Bundle all wiring together in one conduit or wire chase for neatness. 12V DC and 120V AC wires sharing a conduit can cause interference and safety issues.
✓ What to do: Run 12V DC and 120V AC wiring in separate conduits. Label everything clearly. Mark your AC wires with a permanent marker or use colored wire from the start. This also makes future troubleshooting dramatically easier.
07
Undersizing the Battery Bank "To Save Money"
❌ What people do: Buy one 100Ah lithium because it fits the budget, planning to "add another later." The second battery never gets added, and they spend a year managing constant power anxiety.
✓ What to do: Budget for your full battery bank from the start. Calculate your actual daily usage (our solar guide has a calculator), add 30% buffer, and buy that much capacity upfront. Adding batteries later means rewiring the system. Do it right once.
08
Wiring Solar Panels in Series Without Checking Voltage Limits
❌ What people do: Wire 3× 100V panels in series, generating 300V open circuit, then connect to a charge controller rated for 150V max. This destroys the controller instantly.
✓ What to do: Add up your panel open-circuit voltages (Voc) for series strings. This must stay below your charge controller's maximum input voltage with a safety margin. When in doubt, wire in parallel (same voltage, higher current) rather than series.
09
No Shore Power / AC Charging Option
❌ What people do: Build a solar-only system with no way to charge from shore power. Works fine until 5 cloudy days in a row, a long time parked in a tree-covered campsite, or a winter trip to the Pacific Northwest.
✓ What to do: Install a DC-to-DC charger or a proper AC converter/charger so you can plug into shore power when solar falls short. The Victron IP22 or Sterling Power B2B charger are solid options. This is a $100–$300 addition that saves the trip when solar isn't enough.
Wire Gauge Quick Reference
| Wire Size | Max Amps (chassis) | Common Uses |
|---|---|---|
| 18 AWG | 16A | LED lights, small accessories |
| 16 AWG | 22A | USB chargers, small 12V devices |
| 14 AWG | 32A | Fan, water pump, outlets up to 15A |
| 12 AWG | 41A | Fridge, 20A circuits |
| 10 AWG | 55A | Shore power input, small inverters |
| 8 AWG | 73A | Medium inverters up to 1000W |
| 4 AWG | 95A | Large inverters, solar charge runs |
| 2/0 AWG | 190A | Main battery cables, 2000W+ inverters |
| 4/0 AWG | 260A | Large battery banks, 3000W+ inverters |