10 Common Van & RV Electrical Mistakes (and How to Avoid Them)
After seeing a lot of van and RV electrical builds, the same mistakes show up again and again — most of them avoidable with a bit of planning. Here are the ten most common, and how to sidestep them.
Avoid these mistakes from the start
Our free calculator sizes your wire, fuses, and battery correctly based on your actual build — no guesswork.
1. Sizing wire for current only, not voltage drop
A wire can be rated for the current and still cause significant voltage drop over a longer run, dimming lights and reducing charging efficiency. Always check both ampacity and voltage drop — see the AWG wire size chart.
2. Skipping or misplacing the main battery fuse
The main fuse must be within about 7 inches of the battery's positive terminal — not somewhere convenient down the line. Skipping it (or placing it too far away) leaves the entire cable run unprotected. See the fuse sizing guide.
3. Using a standard fuse on a LiFePO4 main circuit
LiFePO4 batteries can deliver very high short-circuit current. A standard ANL or blade fuse may not have the interrupt rating to safely break that fault — a Class T fuse is the correct choice for the main fuse on a lithium bank.
4. Not accounting for smart alternators
Many vehicles from the last decade have smart (variable-voltage) alternators that won't reliably charge a house battery through a direct connection. A DC-DC charger with the correct trigger setup is required — see DC-DC charger sizing.
5. Charging LiFePO4 below freezing
Charging LiFePO4 cells below 32°F (0°C) causes permanent damage. A good BMS blocks this automatically — but that means charging simply won't work in cold weather unless the battery has self-heating, like Battle Born's heated line. See LiFePO4 vs AGM.
6. Multiple ground points
Bonding the system negative to the chassis at more than one point creates ground loops that can cause stray currents, corrosion, and erratic readings on battery monitors. One deliberate bond point only.
7. Oversizing the inverter "just in case"
A bigger inverter than you need adds cost, standby drain, and demands heavier cable and a bigger fuse for no benefit. Size it to your actual loads plus ~25% headroom — see sizing an inverter.
8. DIY work on the 120V side
The 12V DC side is reasonable for a careful DIYer. The 120V AC side — shore power inlet, breaker panel, GFCI, any fixed inverter output — falls under NEC Article 551 and should be installed or inspected by a licensed electrician.
120V mistakes are the dangerous kind
A mis-wired 120V circuit can be lethal and isn't always obvious from the outside. If you're not confident on the AC side, get it inspected — it's a small cost relative to the risk.
9. Mismatched charge profiles across multiple chargers
If solar, DC-DC, and shore power all charge the same LiFePO4 battery, all three need a LiFePO4-compatible profile. A single charger left on an AGM profile can undercharge the battery or cause the BMS to behave unexpectedly.
10. No way to monitor the system
Without a battery monitor (shunt-based, like a Victron SmartShunt), you're guessing at state of charge — which leads to either running the battery too low (shortening its life) or topping off more than necessary. A monitor is one of the highest-value additions for ~$120.