A widely used rule (from NEC-style continuous-load practice) sizes overcurrent protection at 125% of continuous current, rounded up to the next standard size, while never exceeding the ampacity of the wire it protects. Put the fuse as close to the battery positive as practical. Lithium banks can deliver very high short-circuit current, so many manufacturers specify a Class-T fuse at the battery. Solar strings use the panel maker's maximum series fuse rating. Your equipment manual overrides any rule of thumb.
| Continuous A | Fuse |
|---|---|
| 10 | 15 |
| 20 | 25 |
| 30 | 40 |
| 40 | 50 |
| 60 | 80 |
| 80 | 100 |
| 100 | 125 |
| 150 | 200 |
| 200 | 250 |
Safety: These are general estimates, not a design. Follow your equipment manufacturer's instructions and local electrical code, and consult a qualified electrician for anything connected to shore power, a house, or high-current batteries.
At 12 V a 2,000 W inverter can draw about 185 A continuous; 125% is about 231 A, so the next standard size is 250 A, with wire rated for it (often 2/0–4/0). Follow the inverter manual's specified fuse.
Both work if they are DC-rated for your voltage and interrupt current. Breakers can double as disconnects.
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