Electrical safety
Fuses, Wire Size, and Not Melting Your Rig
Batteries do not usually cause electrical fires by themselves. Improper wiring does. The purpose of a fuse is not to protect your device. The purpose of a fuse is to protect the wire.
Why this matters
A 200Ah LiFePO4 battery is capable of delivering huge current. Without a fuse, a short circuit can turn a cable into a heating element.
Fuse placement
Every positive wire leaving the battery should be fused as close to the battery as practical. Not eventually. Not somewhere down the line. Close to the source.
Basic wire size categories
| Load type | Example wire | Common uses |
|---|---|---|
| Small loads | 16 AWG | Lights, USB charging, small accessories |
| Medium loads | 10 AWG | Fridges, DC outlets, moderate accessory runs |
| Large loads | 4 AWG or larger | Inverters, DC-DC chargers, battery connections |
These are broad examples. Final wire size depends on current, fuse size, cable length, insulation rating, and acceptable voltage drop.
Voltage drop
Long wires lose voltage. Undersized wire can create hot cables, lower device voltage, and poor efficiency. A fridge at the end of a long skinny cable may shut off even when the battery is not empty.
Common mistakes
- No fuse near the battery
- Wrong fuse size
- Cheap wire that is not real copper
- Undersized wire for the load
- Poor grounds and loose crimps