Posted by Sherman in Idaho [209.33.95.254] on Sunday, January 04, 2015 at 12:25:21 :
In Reply to: battery cable shortened = success!! posted by scott 56 [24.130.235.145] on Saturday, January 03, 2015 at 16:43:50 :
A little bit of resistance makes a huge difference with starter cables. At 100 amps, which is a reasonable draw for a starter on a small, old engine(300 or more more for a big tight V8), 10 milliohms, which you'll never measure with an ohm-meter, means a 1 volt drop, which when you only have maybe 11 volts to start with, is significant. The jumper cable vendors try to claim that #4 wire is super heavy duty, and the really cheap cables have only #8 wire (but lots of insulation to make them look fat). If you were wiring up a house, #8 would be rated for 40 amps and #4 for 70 amps, and that's based on overheating of the wire, not on wasted voltage. In a 6 volt system, you need twice as much copper for the same amount of starter power as at 12 volts. It's tough to over-do it in terms of battery cable size, especially with jumper cables or if the battery is mounted some distance from the starter.
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