Amps Draw and Voltage Drop Question 2
Question 2 -17 Oct -------- There are no dumb questions--until now! If the furnace draws 8 amps and there is a 0.2v drop when it is on, and you change the positive wire to the furnace to a fatt...
Forum Discussion
BFL13 wrote:
DC-DC in thread about that last Spring it came out that if you used thin wire the draw on the alternator would be 30 amps for a 20 amp output, but if you used fat wire, that draw was much less, but still above 20 of course.
OK, got it!
Yes, feeding a DC to DC charger with a wire ga of sufficient size that will have much less voltage loss because the resistance of the wire is much lower.
Yes, the draw will be more than 20A with a larger wire to a DC-DC charger but will be less than if you feed it with a small wire ga that has higher resistance..
The key here is with high amperage 12V items, use as large of wire and as short of a run as possible. Yes, 12Ga wire will support 20A, but as the run gets longer the resistance of the wire adds up zapping your voltage at the end of the line.
Wire resistance is a big issue when it comes to high current 12V items. Basically in 12V battery world we are talking a operating voltage range of 1V-2V between fully charged to a dead battery.. That means every tenth of a volt reduction in voltage drop means a lot. Comes into play especially when you are dealing with heavily discharged batteries.
