[PSUBS-MAILIST] Battery Wires Too Long

[Alan via Personal_Submersibles]

Just passing on this link about battery wire length to speed controller that
I think is reasonably important.
https://www.rcgroups.com/forums/showthread.php?952523-too-long-battery-wires-will-kill-ESC-over-time-precautions-solutions-workarounds
As a rule of thumb it is suggesting adding 220uf extra capacitance for every
4" of wire from battery to electronic speed controller. 
The other suggestion is that where possible lengthen the wires from the 
speed controller to the motor rather than battery to speed controller.
Below is a quote from a guy that has been designing motors & controllers
for 30 years.
Alan

I will repeat the message previously given. I hope you heed some sound advice
based on theory and practice.
1. wire resistance my rob you of a bit of power but will not destroy
your speed control or motor.
2. wire inductance will not damage your motor nor will you be able to
detect any effect even with 100 feet of wire.
3. wire inductance will kill the mosfets in your control and may even blow the caps
I am a design engineer and manufacturer of motors and controls for over 30 years.
you must keep battery wires as short as practical . short means 1 foot or less.
brushed or brushless makes no difference.

here are some example of problems some customer have had
1. blimp 30 feet of wire to speed control and steering motor in the tail.
control voltage rating 60 volts 50amps motor load 12v 20 amps
result instant smoke first run of motor. I replaced control at no
cost . same result instant smoke. then i was told about long wires
ran a test with 3 ft cord result 30 volt swithching spikes on 100 uf input cap.
had customer put control near battery in gondola. 30 ft wire to motor
end of problems.

we have customers running very long wires to motors for industrial applications
with no problems. hundreds of feet or more.

on robots running two or more motors on one battery. 2 feet battery wires
to non opto coupled controls will make motors hunt. no problem with
opto coupled controls. with BEC controls keep battery wires short. PERIOD
astrobob

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