Like most car enthusiasts, you’ll want to add some modern comforts to your classic or muscle car – and that means an alternator upgrade to power them all. In the early days, there wasn’t much need for high-amp alternators because the only accessory they really had to deal with was an additional pair of speakers in the back. But after the 1980s, accessories became more popular as fog lights, sound systems, electrical fans, air suspensions, sophisticated alarms, cameras and more slammed the market.

With many older alternators, the 14-16 gauge wiring alone can’t handle more than the 45-60 amps factory alternators were putting out – and upgrading the wiring is a daunting task. Fortunately, there are great one-wire alternator solutions that use a single wire to connect the alternator to the battery. The voltage regulator is internal and no other wires need to be connected to your electrical system (except a good ground).

But that connection between the alternator and the battery is very important. Using too small of a charge wire or improperly attached terminals could result in voltage loss. When upgrading your alternator you have increased the volume of current, and in most cases you will need to increase the size of the charge wire to accommodate the increase in amps.

Recommended Charging Cable Gauge Size

AMPS	Up to 4′	4-7′	7-10′	10-13′	13-16′	16-19′	19-22′	22-28′
35-50	12	12	10	10	10	8	8	8
50-65	10	8	8	6	6	6	6	4
65-85	10	8	8	6	6	4	4	4
85-105	8	8	6	4	4	4	4	2
105-125	6	6	4	4	2	2	2	0
125-150	6	6	4	2	2	2	2	0
150-175	4	4	4	2	2	0	0	0
175-200	4	4	2	2	0	0	0	00

Source: Powermaster Performance