David Gower

G'day

Quick question - Is there any problem with having somwehat longer leads from the LiPo powerpack to the ESC? Not too much longer than normal, but enough to fit in an outside disarming switch into the line for safety reasons. This would be fitted into an e-sailplane's nosecone which has no canopy or hatch, and would be similar to this - http://www.espritmodel.com/index.asp...OD&ProdID=5527 - which comes from Esprit Models in FLA I appreciate that motor leads should not be shortened, and probably the leads from the ESC to the motor either, and that all power leads should be kept as short as practical, but I was hoping an extra few cms (or an inch or two) between the LiPoi and ESC through a switch would not be problem. []

Regards

David.

Red Scholefield

My Feedback: (9)

LONG BATTERY TO ESC WIRES OR LONG MOTOR WIRES FROM ESC?

There has been a fair amount of controversy on this subject as e-flighters move into multi-engine models. Logic would tell us that just lengthening the battery leads so the ESCs could be located in the engine nacelles for cooling would be the way to go. Well that isn’t the way it goes according to those that design the ESCs.

Patrick del Castillo of Castle Controllers has this to say, “On the HV controllers especially, the battery-ESC length is the critical length. You should not extend the wires more than a total length of greater than 12" without additional capacitors. On the motor side, length is less critical 18" is fine.

While Bob Boucher (Astrobob) http://www.astroflight.com has this to say on the subject with a bit more detail,
“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.

You must keep battery wires as short as practical. Short means 1 foot or less.
Brushed or brushless, it makes no difference.

Here are some example of problems some customer have had;
1. Blimp with 30 feet of wire to ESC near the steering motor in the tail.
ESC rating 60 volts 50amps, motor load at 12v was 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 and ran a test with 3 ft cord result 30 volt switching spikes on 100 uf input capacitor. I had the customer put the ESC 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.

With ESC keep battery wires short. PERIOD!

But if you must run long battery leads Shultze shows us how to add extra capacitors (English and German): http://www.schulze-elektronik-gmbh.d...e/gfutc-de.pdf

David Gower

Thanks Red

That answers my question in far more detail than I expected. Like I noted originally, there would only be amatter of an additional 4 or 5" max, between the LiPo and ESC, probably a lot less as I intend to make up the 'ignition key' myself, and will make is short as possible.

Regards from Oz

David.

lejongleur

My Feedback: (10)

I recently posted a virtually identical question (somewhere) on RCU. Based on the responses, the information above is exactly correct.

For my application, I made up some big fat extension wires 13 cm long from ESC to motor, using 4mm bullet connectors. I put a watt meter on before and after. Here are the results for an E-Flite Power 32, 13x6 prop, 4S lipo.

Direct connect - 780+ watts
With 13cm extensions - 760 watts, a 2.5% drop in power. Not too bad.

cyclops2

When 13 cm ( 5.1" ) causes a 2.5 % drop in power. The wire is way too small.

A 4' extension should show NO measurable voltage or power drop, ever.

sparky925

My Feedback: (1)

Sorry Cyclops, but i beg to differ!
A 4 ft extension can and will show a very measuravle differance.
I have recently used a power supply for power to an ESC and brushless motor.
using no extensions on a 35 amp ESC and pulling 40 amps i have 532 watts, but when i use 24" of the same 16 guage as comes on the ESC i onlt got 520 watts. that alomost 2% loss over 24". That would be almost 4% over 48" at about 505 watts! \
The only way i got almost 0 loss was with a 24" 12 gauge extension. i got 1 watt loss on 24" so 48" would still Be 2 watts!

Just my 2 cents

cyclops2

You may not realize what amount of excessive current you are putting thru the wires. So I am posting a accurate chart to help people use # 14....#12......#10....and larger guages, to prevent melted wires, charred connectors & low power of the drive.

Should the wires melt and touch, the short circuit can & has caused LIPOS to catch fire for no apperant reason.