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Old May 12, 2002, 10:25 PM
Tasmanian Tiger
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Hobart, Tasmania, Australia
Joined Aug 2000
273 Posts
Capacitor for long wires between BL ESC and battery

Hi all.

OK, I have a Jeti 40A BEC brushless controller (gold label) and the model I am going to put it in requires me to have about 300 to 400mm of wire between the batteries and the controller. Jeti state that the wires between the battery and controller should be no longer than 200mm. As I understand it there is some problem with voltage spikes building up along long wires. Any way to overcome the problems it has been recommended that an extra capacitor be placed between the pos and neg wires to soak up the voltage spikes.

My questions are, what type, and rating of capacitor should be used and where should it be placed in respect to the controller and battery?

Thanks for your time

Dean
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Old Jun 03, 2002, 08:17 PM
Tasmanian Tiger
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Hobart, Tasmania, Australia
Joined Aug 2000
273 Posts
OK, I will answer my own question.

I wrote to Jeti with this question and received the following reply the very next day:

If you use 300 mm between controller and battery it is no problem. If you
need more than 300 mm it is necessary to add capacitor between red (+) and
black (-) wires at 50% of length. If it is nescessary I send you capacitor
( special ) to add it to the wires.


Best regards J.Tinka

So I said yes please send me a capacitor. They actually sent me 4 capacitors and they arrived last Friday.

I must say this is great service from Jeti.

I hope this helps anyone else in the same situation.

Cheers

Dean
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Last edited by DeanW; Jun 03, 2002 at 08:19 PM.
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Old Jun 03, 2002, 08:18 PM
Tasmanian Tiger
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Hobart, Tasmania, Australia
Joined Aug 2000
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This is what one side of the capacitor looks like
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Old Jun 03, 2002, 08:18 PM
Tasmanian Tiger
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Hobart, Tasmania, Australia
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and this is the other
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Old Jun 03, 2002, 08:27 PM
BEC
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Auburn, Washington USA
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Good to hear this......

Lengthening wires, and on which end of the controller is is safer to do so, is an area where makers vary widely. I'm glad Mr. Tinka was able to answer (and provide parts). I'll try to remember this the next time I get the question.
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Old Jun 03, 2002, 08:42 PM
RIP Ric
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Marietta, GA
Joined Jun 1999
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I see a 220uF, but the other? Any idea?
Still, any cap in this order of magnitiude should be OK, I guess..
..a
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Old Jun 03, 2002, 08:55 PM
Tasmanian Tiger
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Hobart, Tasmania, Australia
Joined Aug 2000
273 Posts
Andy,

The photos are the two sides of the same capacitor, the first photo shows its rated to 105 dec C the second shows its rating 220uF 35V. The 4 caps Jeti sent me are the same so I will have 3 spare for future needs.

Cheers

Dean
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Old Aug 24, 2002, 03:53 PM
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United States, TX, Midland
Joined Apr 2001
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re: input filter caps

having recently had this problem with my Kontronik 3SL controler I have learned from the "experts" that the type of cap to use is a low ESR rated cap. This is a capacitor that is designed for switching power supplies and will tolerate high ripple currents. As for the uf rating, more is better limited by the physical size of the cap. Also recomended is a voltage rating at least twice the voltage of the largest battery pack you will use. I ended up using a 1000uf low ESR cap ordered from Mouser Electronics. Cost about $3. Before I learned this I tried a standard Radio Shack cap. The wires glowed red hot before they finally melted and the cap fell off. This happened real fast, before I could even pull the throttle back. BTW, ESR stands for "low equivilent resistance". Hope this helps.

John
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Old Aug 24, 2002, 06:31 PM
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and all this time i thought ESR meant " Equivilent Series Resistance" ......... you learn something all the time .............. kw
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Old Aug 24, 2002, 06:35 PM
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or even " Effective Series Resistance "......... i like this one even better !!!!!! ............ kw
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Old Aug 25, 2002, 09:25 AM
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United States, TX, Midland
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re: ESR

Oops, yes it is equivilent series resistance. I was thinking that and I even previewed my post and still didn't catch it. It must be ESO (Early Senility Onset).
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Old Aug 25, 2002, 10:25 PM
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Folsom,Ca,USA
Joined Apr 2001
992 Posts
Hi,

I had a similar problem with a scratch built pusher prop 50" Lockeed T-33 with a Phasor 30/3, 12 cells, BEC not in use.
Instructions warned that 20 cm was max battery to esc.

So I put the esc by the battery and exteded the motor leads 24" (600mm)

Works fine. Motor runs and starts like it still had short leads, no problems.

Plane flew for the first time this weekend with no problems

Wonderful power system!! Smooth strong rush of power accelerated 6+ lb plane to flying speed in about 200 ft ( good for a model jet, they need speed) lifted off, Pulled up the gear and away it went!!
What a relief!! Took months to build.

Perfect motor response for whole 6 minute flight
(Missed the first approach)

Love that motor!!

And the gear came down and locked for landing too!

Life is good

DaveW
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Old Oct 02, 2013, 11:14 PM
Explorocam
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Canada, ON, Ottawa
Joined Feb 2012
429 Posts
Quote:
Originally Posted by DeanW View Post
OK, I will answer my own question.

I wrote to Jeti with this question and received the following reply the very next day:

If you use 300 mm between controller and battery it is no problem. If you
need more than 300 mm it is necessary to add capacitor between red (+) and
black (-) wires at 50% of length. If it is nescessary I send you capacitor
( special ) to add it to the wires.


Best regards J.Tinka

So I said yes please send me a capacitor. They actually sent me 4 capacitors and they arrived last Friday.

I must say this is great service from Jeti.

I hope this helps anyone else in the same situation.

Cheers

Dean
I'm about to add capacitors to my 40Amp battery wires to combat the inductance problem.
Could you send an example of how you would wire these so as to make sure the positive and Negative can't possibly touch?

My idea.
I am planning to open the sheath at 50% mark and slip the terminals under the sheath and then solder to hold in place. Then I'll coat everything in Liquid Electrical tape, but I'm not sure if I should cover the capacitor as well or just coat up to the capacitor.

I was also wondering if I should make some of holder for the capacitor that can sit between the two terminals but must be small enough to fit inside a 25mm diameter carbon tube. I think the Liquid Electrical tape should be fine, but not sure.
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Old Oct 03, 2013, 01:03 AM
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Australia, VIC, Melbourne
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The tape should work, personally I would use normal electrical tape (or something else) and tape the cap to the wires so it cant vibrate. Should be all thats needed
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Old Oct 03, 2013, 02:40 AM
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Quote:
Originally Posted by Exploroman View Post
...I am planning to open the sheath at 50% mark and slip the terminals under the sheath and then solder to hold in place. Then I'll coat everything in Liquid Electrical tape, but I'm not sure if I should cover the capacitor as well or just coat up to the capacitor.

I was also wondering if I should make some of holder for the capacitor that can sit between the two terminals but must be small enough to fit inside a 25mm diameter carbon tube. I think the Liquid Electrical tape should be fine, but not sure.
Remember, carbon fibre conducts electricity

I've never used liquid tape, but the way I would do it is cut a small piece out of the sheath, as you plan to do, and solder the capacitor in place, leaving it standing about 1/2" above the cables. Then I would fold it back so that the capacitor and its wires lies flat against the cables, and install heatshrink to cover each joint and the 1/2" of capacitor wire. For installation in a carbon tube I would then use a large-diameter heatshrink to cover the whole capacitor and cables, just to be sure.
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