Wire Length to Motor vs ESC from battery - RC Groups
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Jun 27, 2008, 11:16 AM
Registered User

Wire Length to Motor vs ESC from battery

I have my HV ESC (Large 4-Motor Bomber) mounted at each nacell next to motor. I have the battery wire from each ESC running back to batteries to be located in main fusilage. The battery wires to ESC are quite long at about 3 ft. I read this am that I need to have the long wires (36" +/-) between motor and ESC and short wire (18" or less) between ESC and battery to avoid adding capacitors or something. I hate to rewire every thing but will do what is required. The batteries will not fit in the outer nacells but I have plenty of room for them in the fusilage and can provide good ventilation.
I am using the Turnigy "Sentilon 100A-HV ESC's with Astro 5020-30 motors
Need help -Thanks
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Jun 27, 2008, 12:47 PM
jrb's Avatar
Info I found soemtime ago: http://www.schulze-elektronik-gmbh.com/tips_e.htm .

“Electronic speed controllers have been designed to operate correctly with a cable length between battery and controller at a maximum of 20 cm (7 inch) each lead.
In some installations it will be necessary to increase the length of the battery cables. In this case it is necessary to install additional low-ESR decoupling capacitors. The installation of these additional capacitors allows the increase to a total length of battery cables to as much as 30-50 cm (12-20 inches), depending on the motor load or 30 cm when using not inline (not end-to-end) soldered packs (12“ pos.+ 12“ neg. cable between "saddle-packs" and controller).
schulze Order Term: cap-330µ/50V (2 pieces - up to 32 Ni-Cd/Ni-MH cells / with mounting instruction).
schulze Order Term: cap-330µ/16V (2 pieces - up to 11 Ni-Cd/Ni-MH cells / with mounting instruction).”
Jun 27, 2008, 08:28 PM
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BEC's Avatar
This is what Patrick DelCastillo (founder, CEO and chief designer at Castle Creations) said about this: https://www.rcgroups.com/forums/show...8&postcount=14

I was going to suggest you ask the ESC maker what the best course was until I saw that they're Hobby City ESCs. Not likely to get a lucid answer if you get one at all.

I have seen input capacitors explode with long battery leads. It's not pretty. I also know from sad experience that much of this Chinese stuff is overrated (ratings quoted, if trusted, lead to immediate failure under NORMAL conditions).

What is the claimed voltage rating of these controllers and what battery are you using? The safest course is probably to use auxiliary input capacitors as described by the quote from Matthias Schulze. Note that the voltage rating on those added capacitors must be quite a bit higher than your battery voltage. You see, what's going on here is that - on the battery side - the controller starts and stops the flow of current at whatever the switching rate of the controller is. Long leads form an inductor and this start/stop gives you voltage spikes. The longer the leads the higher the added voltage from that inductance. Think "water hammer" with electricity.

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