Size DC cable by continuous amps and run length, then fuse every positive cable to its capacity. A 12V/3000VA Victron MultiPlus pulls roughly 250–300A and needs 2/0–4/0 AWG cable with a 300–400A fuse mounted within about 7 inches of the battery. This chart gives you starting-point cable and fuse sizes for common Victron RV components — always confirm against your unit's manual and keep voltage drop at or below 3%.
How to size DC cable (the method)
Three things drive cable size: current (amps the device draws), length (total positive + negative run), and acceptable voltage drop (aim for ≤3% on power circuits). Higher current or longer runs both mean thicker cable.
- Find the device's continuous current (watts ÷ system voltage, or the spec sheet).
- Measure the round-trip cable length.
- Pick the gauge that keeps voltage drop ≤3% at that current and length (use the chart below as a start).
- Fuse the positive cable to protect the cable, mounted close to the battery.
Inverter / charger cable & fuse chart
Starting-point sizing for Victron inverter/chargers. Longer runs need a larger gauge.
| Unit | Approx. max DC current | Cable (typical) | Fuse (typical) |
|---|---|---|---|
| 12V / 1600VA MultiPlus | ~150A | 1/0 AWG | 200A |
| 12V / 2000VA MultiPlus | ~190A | 2/0 AWG | 250A |
| 12V / 3000VA MultiPlus | ~250–300A | 2/0–4/0 AWG | 300–400A |
| 24V / 3000VA MultiPlus | ~150A | 1/0–2/0 AWG | 200A |
| 24V / 5000VA Quattro | ~250A | 2/0–4/0 AWG | 300A |
Installing one of these? See how to install a Victron MultiPlus.
Solar / MPPT cable sizing
Solar has two sides with different needs:
- PV side (panels → controller): sized to the array's short-circuit current; often 10–8 AWG for typical RV arrays.
- Battery side (controller → battery): sized to the controller's max output current (e.g. a 50A MPPT → ~6 AWG, fused ~60A).
Match the controller to the array first — see MPPT vs PWM and shop charge controllers.
Busbars, Lynx & fuse types
For any build with more than a couple of DC connections, use a busbar or a Victron Lynx distributor instead of stacking lugs on the battery terminal. It gives you one clean, fused distribution point.
Fuse types you'll see:
- MEGA / ANL — common for inverter and main DC circuits.
- Class-T — high interrupt rating, preferred for lithium banks feeding big inverters.
- MIDI / blade — for smaller branch circuits.
Shop fuses and cables & interfaces.
Common mistakes to avoid
- Fuse too far from the battery — it must sit close to the positive terminal to protect the whole cable.
- Undersized ground/negative — size the negative the same as the positive.
- Mixing fuse types/ratings — match interrupt rating to the battery's potential fault current (lithium → Class-T).
- Ignoring run length — a gauge that's fine at 1 m may drop too much voltage at 4 m.
Frequently asked questions
What size fuse for a 3000VA MultiPlus?
For a 12V/3000VA unit, a 300–400A fuse close to the battery with 2/0–4/0 AWG cable is typical — confirm the exact value in your Victron manual.
Class-T vs MEGA fuse — which do I need?
Class-T has a higher interrupt rating and is preferred for lithium banks feeding large inverters; MEGA/ANL suit many standard DC circuits. Match the fuse's interrupt rating to your battery's fault current.
Do I fuse the negative cable?
No — fuse the positive cables. The negative/ground is sized to match but isn't fused in a standard single-battery DC system.
How close to the battery should the fuse be?
As close as practical — typically within about 7 inches (18 cm) of the positive terminal — so the entire cable downstream is protected.
Building your Victron system? Shop Victron cable, fuses, Lynx & busbars — in stock, ships from Upland, CA.