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Amps and Wire Gauge - 12V Circuit
Maximum current - amps - through a 12V circuit in combination with size (AWG) and length of wire
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In an electrical systems the conductors should not be sized with voltage drops exceeding 3%. For a 12V system the maximum voltage drop should be less than 12 (V) x 3% = 0.36 (V).
The table below can be used to determine the combination of maximum current through a 12V electrical wire, size (AWG) and length of cable.
| American Wire Gauge (AWG) | ||||||||||
| Length (feet) |
Current (amps) | |||||||||
| 5 | 10 | 15 | 20 | 25 | 30 | 40 | 50 | 60 | 70 | |
| 15 | 16 | 12 | 10 | 10 | 8 | 8 | 6 | 6 | 4 | 4 |
| 20 | 14 | 12 | 10 | 8 | 8 | 6 | 6 | 4 | 4 | 4 |
| 25 | 14 | 10 | 8 | 8 | 6 | 6 | 4 | 4 | 2 | 2 |
| 30 | 12 | 10 | 8 | 6 | 6 | 4 | 4 | 2 | 2 | 2 |
| 40 | 12 | 8 | 6 | 6 | 4 | 4 | 2 | 2 | 1 | 1/0 |
| 50 | 10 | 8 | 6 | 4 | 4 | 2 | 2 | 1 | 1/0 | 1/0 |
| 60 | 10 | 6 | 6 | 4 | 2 | 2 | 1 | 1/0 | 2/0 | 2/0 |
| 70 | 10 | 6 | 4 | 2 | 2 | 2 | 1/0 | 2/0 | 2/0 | 3/0 |
| 80 | 8 | 6 | 4 | 2 | 2 | 1 | 1/0 | 2/0 | 3/0 | 3/0 |
| 90 | 8 | 4 | 4 | 2 | 1 | 1/0 | 2/0 | 3/0 | 3/0 | 4/0 |
Note! Failure to use an adequate size may result in fire. Always secure a wire with a fuse.
- 1 ft (foot) = 0.3048 m
Wire Gauge Design Procedure
- calculate the total length of the wire from the source to the device and back again
- determine the amount of current in the wire
- correct wire gauge is in the intersection of amps and feet
Note! The wire size is required for a 3% voltage drop in 12 Volt circuits. Oversize the wire if the voltage drop is critical.
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