What gauge wire for a 3,500 watt amp?
A 3,500 W RMS class D amp draws about 317 A at full power: more than one 4/0 run carries. Use two power runs or a distribution block with fused leads, and plan it with an installer.
A class A/B amp of 3,500 W draws more, about 507 A, and takes a split the load fuse.
Power and ground wire gauge for a 3,500 W amp
Power and ground wire gauge for a 3,500 W amp| Power run | Class D copper | Class D CCA | A/B copper | A/B CCA |
|---|
| 5 ft | 4/0 | two runs | split the load | split the load |
|---|
| 10 ft | 4/0 | two runs | split the load | split the load |
|---|
| 15 ft | 4/0 | two runs | split the load | split the load |
|---|
| 20 ft | 4/0 | two runs | split the load | split the load |
|---|
| 25 ft | 4/0 | two runs | split the load | split the load |
|---|
Current draw and fuse for a 3,500 W amp
Current draw and fuse for a 3,500 W amp| Amp class | Current draw at full power | Fuse at the battery |
|---|
| Class D | 317 A | 350 A |
|---|
| Class A/B | 507 A | split the load |
|---|
Good to know
Use the same gauge for the ground, as short as you can, to bare metal on the body or frame.
Several amps on one run: add their RMS watts. With a distribution block, each amp’s own lead can be thinner, with its own fuse.
Method: current at full power = RMS ÷ efficiency (class D 80 %, A/B 50 %) ÷ 13.8 V; the next standard fuse; the thinnest wire rated for that fuse (33 CFR 183.425 Table 5, 105 °C, × 0.85 for the engine bay; CCA × 0.79) with at most 0.5 V drop over the power run plus 3 ft of ground.
Guidance only, never a safety rating. Follow your amp and vehicle manuals. The fuse protects the wire: put it within 18 in of the battery. Disconnect the battery before you wire.
Wire gauge for other amp sizes
Frequently asked questions
What gauge wire do I need for a 3,500 watt amp?
A 3,500 W RMS class D amp draws about 317 A at full power: more than one 4/0 run carries. Use two power runs or a distribution block with fused leads, and plan it with an installer.
What size fuse for a 3,500 watt amp?
About 350 A for class D, the next standard size above its full-power draw of 317 A, and never bigger than the wire is rated for.
Will my alternator keep up with a 3,500 watt amp?
At full power the amp alone draws about 317 A (class D), on top of the 40–60 A the vehicle uses. Music averages less; check yours with the current draw calculator.