Re-Wiring the brakes.

mrekim wrote:
Here's a nice voltage drop calculator:


http://www.bulkwire.com/wireresistance.asp

Assumptions:
12.8 Volts at battery
4 Ohm per magnet
25 foot cable run


1 10G case:
If the 4 magnet are at the end of 1 10G wire run the the wire "sees" a 1 ohm resistance.

Wire Resistance: .04054.
Voltage at magnets : 12.3 Volts


4 16 G case:
In this case, since there are 4 wire runs, we use 4 ohms as the resistance at the end of the wire.

Wire Resistance: 0.10211
Voltage at magnet: 12.48

So, it appears that home running 16G wire would produce a somewhat better result than running 10G and then a star configuration from there.

I've simplified things and ignored the star at the end of the 10G wire. I'm hoping that simplification isn't skewing things too much...

[ EDIT ]

I redid the math and assumed a 20' run of 10G and then 4 5' runs of 10G. I got 12.52 volts to each magnet that way. So it still seems that, in theory, I would get the same results as as 10G wire.

I also looked for a 2nd way to check my math. The cross sectional area of the 10G wire is 5.26 mm and 16G is 1.31 mm. Well 5.26 / 4 = 1.315, so it appears that 4 16 gauge wires is electrically the same as one 10 gauge.


[ / EDIT ]

Your resistance assumptions need to be doubled since the ground return MUST be terminated at the front of the trailer.. And the ground wire resistance will be the same as the plus wire. Both resistances add together..

So instead of 25ft of wire it is now 50 ft of wire and your resistance from that wire is now double.. Hence the reason as to why going to at least 10 ga wire IS better and doubling up on 10 ga is even better yet..

Additionally any 16 ga wire used will become a "fuse" so to speak if just one of the 16 ga wires (or magnets) happen to short out. A short on the 16ga wire will eventually cause the insulation to melt or burn..

16 ga wire in a very short distance like from the magnet coil to the outside of the drum back is ok since the distance is short and possible damage is minimal..