Ye olde "Don't lengthen the battery(ies) to ESC(s)" debate...anything new?

Wingnutz · October 03, 2015, 06:49:31 PM

Has anybody had ESC problems because the of long leads from ESC to battery?Andre L (my electronics go to guy)says the old guideline of keeping battery to ESC wires short has little or no validity. Other people who claim to know something about electronics say you risk damaging or destroying your ESC(s) if you lengthen the battery(ies) to ESC(s) leads.
I know a number of TEMACers (including me) fly models with long leads between battery(ies) and ESC(s) with seemingly no ill effects.
I'm resurrecting an e-Flite twin engine model where the ESCs are mounted in the wings and the batteries in the fuse, necessitating battery to ESC leads that are long...
Anybody think it's worth the effort to move the ESCs to the fuse to shorten the battery/ESC leads?

Frank v B · October 03, 2015, 09:26:08 PM

Mr. Nutz,

I lengthened the ESC to battery wires on several airplanes (incl. two twins) and no problems. Of course, I never tested regular length versus longer length and measured the change. The motors worked, the plane took off and it landed fine. I just made sure I lengthened both wires the same amount. Passed the acid test. Good enough for me.

I have never lengthened the motor to ESC leads. My rationale: why lengthen 3 wires when you can lengthen 2 and be done with it!
Moral: don't over-think the problem.

Frank

Andy Hoffer · October 03, 2015, 09:43:50 PM

Quote from: Frank v B on October 03, 2015, 09:26:08 PM
Mr. Nutz,

I lengthened the ESC to battery wires on several airplanes (incl. two twins) and no problems. Of course, I never tested regular length versus longer length and measured the change. The motors worked, the plane took off and it landed fine. I just made sure I lengthened both wires the same amount. Passed the acid test. Good enough for me.
I have never lengthened the motor to ESC leads. My rationale: why lengthen 3 wires when you can lengthen 2 and be done with it!
Moral: don't over-think the problem.

Frank

One thing I would never conceive of is accusing Frank of over-thinking a problem!!

Andy

Frank v B · October 04, 2015, 08:51:52 AM

Andy,

re: "One thing I would never conceive of is accusing Frank of over-thinking a problem!! "

...says a problem creator to a problem solver.

Frank

Andy Hoffer · October 04, 2015, 10:52:17 AM

Quote from: Frank v B on October 04, 2015, 08:51:52 AM

Andy,

re: "One thing I would never conceive of is accusing Frank of over-thinking a problem!! "

...says a problem creator to a problem solver.

Frank

Thanks so much Frank. It is most gratifying to finally get some accolades for my main contributions to TEMAC!!

Skyking · October 04, 2015, 12:01:47 PM

Hi Bill,

I have built a couple of planes with really long wires (2' to 3' ) between Battery and ESC.
No problems at all.

wollins · October 04, 2015, 03:22:37 PM

Rule of thumb (as I understand it) is 12" limit for esc to battery ... unlimited for motor to ESC.

Colin

sihinch · October 04, 2015, 03:55:44 PM

I'm only going off what I read from other forums and articles but I understood it to be more risky to increase motor to esc wires. What I understood is that, because the ESC has to control the timing of our motors very accurately, increasing the motor wire increases the risk of timing issues.

So I read that extending the battery wire is safest. But I did read that twisting the wires around each other is better too (to limit impedence?)

wollins · October 04, 2015, 04:15:04 PM

Quote from: sihinch on October 04, 2015, 03:55:44 PM
I'm only going off what I read from other forums and articles but I understood it to be more risky to increase motor to esc wires. What I understood is that, because the ESC has to control the timing of our motors very accurately, increasing the motor wire increases the risk of timing issues.

So I read that extending the battery wire is safest. But I did read that twisting the wires around each other is better too (to limit impedence?)

It's no wonder there is confusion regarding this subject ... my understanding is the complete opposite!

pmackenzie · October 04, 2015, 07:43:45 PM

My 2 cents on this debate:

Longer motor esc wires will cause no problems with timing.
The ESC looks at the phase that is "off" to see when its voltage crosses zero to sync the commutation.

Longer battery to esc wire will cause increased voltage spikes as the FETs in the ESC switch on and off.
This is because the longer wires have high inductance.
Both the FETs and the input capacitors will have a maximum voltage rating.
The AC voltage spikes will sit on top of the DC battery voltage. If they add up to enough to blow the FETs then the ESC will be done.
Same for the input caps. In addition, the input caps will have to absorb these voltage spikes as current into and out of the capacitor.
The current can be enough to damage the capacitors, and in some cases even burn out the leads.

You can get away with longer battery to ESC leads if you don't operate near the voltage and current limits of the ESC.
But if you are near the edge on either one then you run the risk of blowing up the ESC.

Another option is to add additional capacitors to the ESC, look at Colin's build thread for an example of this.

Pat MacKenzie

piker · October 04, 2015, 09:35:55 PM

That was my understanding as well Pat, but not to your level of understanding.

But I did asked the question many years ago, and got that answer from... umm.... Castle Creation guy... name escapes me now. I was really surprised of the answer as I expected short wires between the ESC and motor made sense because of the need for accurate switching, but your explanation for that is a good one. Thanks.

BTW, I've stuck with the "long wires between ESC and motor" on a few planes and it has worked out well, with no mods to the wiring or caps, etc. So that's my vote.

sihinch · October 04, 2015, 09:50:44 PM

Wow! Good to know. I would have done it all wrong.

Thanks Colin, Pat & Robert.

Skyking · October 04, 2015, 10:26:17 PM

Simon,
You don't have to worry about impedance.
I'm 65 and I'm not bothered by impedance.
What does that have to do with motors and stuff anyway?

sihinch · October 04, 2015, 10:29:47 PM

I just find it hard Ken!

eddiecj · October 05, 2015, 12:00:39 AM

I'm surprised that the word (Ohms) has not come into the conversation here haha, the only one that matters, electrical current passing through a wire meets resistance as individual electrons collide with atoms the wire itself is made of, causing a resistance to the flow of electricity which is measured in Ohms. Different types of wires have different resistivity characteristics depending on what they're made of, and the resistance measured in Ohms is directly related to the cables length, material type, and area (cross sectional diameter, having said that, has anyone ever purchased an ESC that came with a recommended wire length? Or a (DO NOT EXCEED 10 inch cable length) warning? I'm guessing not because the measurable difference between a 10 inch wire and 20 inch wire although double the resistance I'll bet is not nearly enough to cause any issues. I'm no electrician, but unless you're planning on putting 50ft of ESC wire in then I'll bet you have nothing to worry about.