Long motor leads

[fly boy3]

Hi all, building a delta type foamy for my grandson with pusher configuration. I need to lengthen the motor leads to enable correct CoG position on plan. Is there a max length to these leads to consider without giving me trouble. Thanks. I could use heavier batt. but I do not wish to add weight if need be. Cheers

[Bob Cotsford]

I've run leads up to about 12-15" without problems, that's at around 200W or so. How far do you need to go?

[fly boy3]

Thanks Bob, I only need around 9-10 inches. Should be fine then. Not a lot of info on the motor exept its a 3000kv BW, on an 1000mah 2 cell lipo, 18amp ESC, 6x4 prop. Not enough experience on leccys to work out the watts. Cheers.

[Tom Wright 2]

Well as a starting point a two cell lipo has a nominal voltage of 8 volts and if the esc is rated at 18amps then the max power chain power capability will be 8 x18 = 144 Watts .

So if you look at the motor specs for the max current rating it will need to be at least 18 amps to achieve 144 Watts .Useing a watt meter is the best way to find the optimum prop for the set up .

Based on the information supplied so far 100 Watts would give decent margins for the motor and esc.

Hope this may be of some help FB3 ,if not just ignore .

Tom.

[Ponty Bri]

Hi Tom

When increasing the length of wire to keep the resistance down then you must increase the thickness of the wire to maintain the same current carrying capability without incurring voltage drop. There is no theoretical limit, just consider the cable to you car's starter motor which takes an enormous current.

Brian

[fly boy3]

Cheers Tom, never thought about checking the spec. Doooah. Its all there Cheers, For Ponti Bri, will do and thanks.

[Frank Skilbeck]

FB3, heres a run on drive calc with a 3,000 kv motor 6 x 4 prop and 2s lipo, based on this an 18A ESC maybe a little marginal.

[Simon Chaddock]

FB3

Just remeber there is no limit on the length of the motor/ESC leads other than the voltage drop but there is on the ESC to battery. Much over 15" and you run the risk of damaging the ESC's smoothing capacitors and when they go the ESC goes as well.

I am running a 5x3 GWS prop on an Emax 2805 3000kV with a 2s and it draws just under 10A static.

Even with the same pitch and diameter the type of prop can make a considerable difference to the current drawn.

[Frank Skilbeck]

Simon, running drive calc as above but with a GWS 5 x 3 prop gives 9.7A so pretty much what you are measuring.

[fly boy3]

Hi Frank, as a new comer to electrics, it took some time to interpret the info, but I bow to your experiance,and during the maiden will fly slower, and mod the fuz. to allow extra ventilation over the ESC. I followed the spec to the letter for this model, and to be fair it said 18-20 amp ESC. Always tight ,I am using the 18a one as it is spare. LoL. Might have to speculate though for a 20a. Afterall the model is a delta type foamy jet, which should be flown fast. Thanks both for the info.