10
AWG
Ω / kft (km)
L in ft (m) Current Load Volts Use Case or Example
14 2.58 (8.51) 6 (2) 2A 13.7 KX3‐only in small car
12 1.62 (5.34) 10 (3.3) 2A 13.7 KX3‐only in pickup truck
10 1.02 (3.37) 15 (4.9) 25A 13.0 KX3 in cab with KXPA100 under seat
8 0.64 (2.11) 25 (8.3) 25A 13.0 KX3 in cab with KXPA100 in trunk
Table 1. Practical wire gauges and lengths for the KX3 and KXPA100 in a mobile setting. DC resistances
shown are at 77 deg F, 25 deg C. Source voltage used is 13.8VDC.
For normally constructed, negative ground vehicles (Unibody), only the positive lead is needed for
power. The vehicle body can and should be used, where possible, as the return or ground. Running a
separate return is generally not necessary and saves money as well. Seat‐mount bolts make good
ground bonds and they’re accessible. You can use them as grounds near the loads.
When you perform your own voltage drop calculations, be sure and include the contact resistance of all
connectors in the series circuit to the load. The table above assumes APP connectors as shown in the
photos.
Figure 5. 40A branch circuit switch on the Civic’s instrument panel. There were two “dummies” in this
panel, so I removed the rightmost one and filled its slot with a Honda standard panel switch
replacement. The KX3 and mount aren’t seen, but they are located directly above this panel. The
microphone cable is shown hanging at the left.
