Longer Power wires on Speed Cotrollers

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Steve Leach
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Longer Power wires on Speed Cotrollers

Postby Steve Leach » June 2nd, 2012, 6:58 pm

Hi,

I have an electrified B25 of around 84 inch span. I have made battery placings in the large wheel nacelles which house the battery and speed controller for each motor. Unfortunately the model seems to be quite tail heavy so an option would be to place the batteries into the main fuselage in a more forward position and so hopefully negate the need for added weight up front. I am aware that extending the power leads as would be necessary, may cause other problems. Has anybody else had similar problems and how were they overcome ?

many thanks in advance.

Cheers Steve

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Chris Bradbury
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Re: Longer Power wires on Speed Cotrollers

Postby Chris Bradbury » June 3rd, 2012, 12:07 am

I would strongly advise against extending power leads by more than a couple of inches on any brushless system. Power leads as with the motors themselves are inductive and the modern brushless motors are essentially a three phase alternating device. What happens is voltage spikes are created by the esc as the phases switch, (and by spike think upwards of 200v even on a 3-4s set up) these spikes are very low ampage (remember there's a big difference between amps and volts) so the battery absorbs them before they can bounce back to the esc. If you extend the wires too much (the limit of length will vary from motor to esc, to brand etc as its down to the capacitors built in to them) then essentially you reach a point where the esc effectively no longer sees the battery and the spikes bounce back to the esc rather than being absorbed. This creates heat issues in the esc capacitors, along with voltage fluctuations and will result in a failure at some point. You may then argue that you could extend the three wires to the motor instead, but again you risk a similar issue, plus the additional problem that you may now effect the timing, which will also stop the motor running.

Now this is for brushless and is a side effect of the pulsing the motor goes through. Brushed is different and far less effected as the power is run smoother.

My advice, which I have done on models like this is to move the receiver battery further forward instead, or even use a bigger one too. Make the weight added to balance the model something useful rather than just extra lead.
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Steve Leach
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Re: Longer Power wires on Speed Cotrollers

Postby Steve Leach » June 3rd, 2012, 12:20 pm

Chris,

thanks for the information. Unfortunately the battery packs are as far forward in the nacelles as they can be so it looks like nose weight will be my only option.

Thanks again,
Regards Steve

Barrie King
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Re: Longer Power wires on Speed Cotrollers

Postby Barrie King » June 3rd, 2012, 1:18 pm

Hi, I ran into similar problems with my Mossie, so moved the 2 lipos from the wheel wells into the nose so extended the power leads by a foot or so and had no problems at all.
Barrie

IVAN GOODCHILD
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Re: Longer Power wires on Speed Cotrollers

Postby IVAN GOODCHILD » June 3rd, 2012, 2:03 pm

Steve - I have designed many large scale electic models such as the A10 Concorde and Mossi all electric powered and all using 2 or 4 power trains. To balance all of these models which have wing spans of 3.5M plus and fus length of 2M plus I have positioned the motor batteries so as to balance the model thereby avoiding the need for additional battery weight. You can extend the length of the battery to esc cable by up to 500 mm by fitting low impedance capacitors across the two power cables every 200mm this takes care of the spikes issue outlined by Chris. As it so happens there is a very good explination and pictures of how to do this on the schulze web site www.schultze-elektronik-gmbh.de. GIven your wing span of 84" you should be able to reposition you batteries in the fuselage and make sure that the cable is rated for the current you wish to draw which is likely to be 6mm not 4mm over that length. Send me a pm if you wish any more info.
regards

Steve Leach
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Re: Longer Power wires on Speed Cotrollers

Postby Steve Leach » June 3rd, 2012, 9:10 pm

Thanks to all for the information received - I will take a look at the schulze website - thanks again.

Regards Steve

Ron Pearman
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Re: Longer Power wires on Speed Cotrollers

Postby Ron Pearman » July 4th, 2012, 8:50 am

The link given by Ivan is incorrect. Should be- http://www.schulze-elektronik-gmbh.de/index_uk.htm
(NO "t")

Steve Leach
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Re: Longer Power wires on Speed Cotrollers

Postby Steve Leach » July 11th, 2012, 5:34 pm

many thanks,

I didn't get any where with the other link.

Regards Steve

Robert Mahoney
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Re: Longer Power wires on Speed Cotrollers

Postby Robert Mahoney » July 11th, 2012, 7:31 pm

Hi, this is what is on there web site! you have to look for their TIPS page
Regards Robert Mahoney

Long battery cables etc. on future and other speed controllers


The future (and other types e. g. smart or slim ) 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).

What can i do to use a future speed controller on battery cables which exceed 20 cm (7 inches)?
What can i do to use a future speed controller with a not inline (not end-to-end) soldered battery pack?
What can i do, when the future-9.xx does not arm and beeps four times?
How do i mount additional capacitors to the battery cables of the future?

Steve Leach
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Re: Longer Power wires on Speed Cotrollers

Postby Steve Leach » July 11th, 2012, 8:44 pm

Many Thanks Robert.

Best Regards Steve


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