How does the length of the battery lead affect performance???

[KingKow]

Hi,
Just wondering, will the length of the battery affect the performance in an electric Heli? Some have really long leads and I think I read that it is not good as it introduces more resistance or something in that line.

Also using the Y cable to connect 2 batteries in series, is it better for it to be short or it is irrelevant?

Thanks for your input.

Cheers

[rexingtheair]

its best to have all the wires as short as possible, the longer the wires the more resistance they produce, meaning less power

[Pinecone]

The difference in resistance isn't that much.

But longer leads between the battery pack and the ESC can cause problems with the ESC. The ESC is constantly switching the current on and off, this leads to the draw from the pack to actually be in pulses. Those pulses, combined with the inductance in the longer wires can lead to voltage spikes and damage to the ESC. It will depend on the wire length, amp draw, and how much capacitance is on the ESC input.

IIRC, most ESC manfacturers say to not increase the length of the battery or ESC leads by more than something like 3". And any Y connector would be counted.

[SNAFU]

Yea Pinecone has it right. When dealing with DC the line loss is very significant over distance. However the distance you'll start to see line loss is like over 40 ft. when dealing with 12-20 Volts. We run into this problem at work when someone decided instead of running the leads for our 2-way radios through the wall on the crane cab, to run the wire down one side of the cab, across the bottom, back up the other side then over part of the top. They couldn't figure out why the radio would shut down every time they would key it up. Duh!

This is also why now have AC power coming into our houses. Originally Edisons' power plants were all DC powered, but the power could only be transmitted a relatively short distance. Sometime around 1890's George Westinghouse invented AC current, with it's ability to be transferred long distances with minimal line loss, it prevailed and is what we power out homes with today.

Sorry didn't mean to give a school lesson here, but I thought it was pertinent.

Bill

[KingKow]

Yea Pinecone has it right. When dealing with DC the line loss is very significant over distance. However the distance you'll start to see line loss is like over 40 ft. when dealing with 12-20 Volts. We run into this problem at work when someone decided instead of running the leads for our 2-way radios through the wall on the crane cab, to run the wire down one side of the cab, across the bottom, back up the other side then over part of the top. They couldn't figure out why the radio would shut down every time they would key it up. Duh!

This is also why now have AC power coming into our houses. Originally Edisons' power plants were all DC powered, but the power could only be transmitted a relatively short distance. Sometime around 1890's George Westinghouse invented AC current, with it's ability to be transferred long distances with minimal line loss, it prevailed and is what we power out homes with today.

Sorry didn't mean to give a school lesson here, but I thought it was pertinent.

Bill

Hey that's cool. Thanks for sharing. We sure learn something everyday.

Cheers
:thumbup:

[Nyther]

Very nicely explained SANFU.:thumbup:

Thanks,
Ken

[Mercuriell]

The Ac vs DC - Edison vs Westinghouse is a fascinating story - Edison promoted DC claiming that it was safer because on trials with the electric chair AC needed less power to fry the hapless victim

[jamesotron99]

Not only that but he fried a live elephant to prove his point, the stubborn bastard :D

[Pinecone]

As I understand it, Nicole Tesla was instrutmental in AC power being the standard.

[pwoodyp]

As I understand it, Nicole Tesla was instrutmental in AC power being the standard.
He was but from what I've read Tesla was working for or under contract or being backed (or whatever they called it) by Westinghouse ... so yes both are correct ;).

[gpach]

More on the AC/DC

The primary problem with DC was that there is no such thing as a DC transformer. Transformers only work with AC.

With any given size of wire there is a certain amount of resistance per length. If you are putting DC or AC down it the losses due to the resistance are relatively the same for the same voltage. The reason AC won out is you can put it through a transformer and up the voltage for transmission. This is why we have 2500 volt and higher transmission lines runing across country, When the power gets to point of use the voltage is dropped down to useable (and safe) levels, again with a transformer. The amount of power lost in the lines is a function of the current in the line. By increasing the voltage, you decrease the current. By decreasing the current you reduce the losses. If the power lines across country had to be 120 or 220 volt, the losses would be prohibative as would the required wire size.

EG

If we put 120 volts in and and want to move 10 000 watts through
P = E*I we need 83 amps.

If we have 2500 volts we will only need 4 amps.

In addition to reducing the losses on the line by going to high voltage, they also reduced the requirement for conductor sizes.

[Rick Rotorhead]

Yeah, its the Current draw that creates the heating effect that wastes energy.
As I recall from my school physics the rate of energy loss (in Watts) is:
Resistance (in Ohms) xCurrent(Amps)xCurrent(Amps)

So, doubling the current leads to 4x the wasted heat
So for any given power transmission, higher voltage reduces the current drawn and therefore very significant drop in heating of the conductor. Of course, extreme voltages also lead to arcing and contact breaker damage due to pitting, cant win 'em all..........

[Pinecone]

BTW the top line on the poles in your neighborhood run at 9.7KV, further upstream probably runs 19.2KV in the US, and cross country transmission lines can run up in the 225 KV range.

So down your street that 10,000 watts runs 1.03 amps and cross country is it a whopping 0.0044 amps. :)

[Steel Butcher]

The development of power electronics have allowed for DC transmission. The losses are a bit lower and it comes with other advantages / disadvantages.

[ct420]

I'm glad to see that Nikola Tesla's name at least came up once or twice during this thread. The man was a true genius, and our modern world absolutely would not exist as we know it had he never been born.

After all, he is the one that invented radio control in the first place. His first practical test was with a small electric powered boat. He could send a signal that turned the rudder. This was in the early 1900s, remember!


It's a real crime how history has virtually ignored Tesla. He was a bit of an odd-ball, but I can't think of any single person who has contributed more to the modern era than him. If you ever get some time, do some research on Tesla. You'll be shocked at all the discoveries and inventions he produced.

Hell, even Marconi (credited with inventing the radio) had to use about 10-15 of Tesla's patents relevant to radio transmission to pull that off :)

[Rick Rotorhead]

Tesla, hmm, didn't he invent the 'coil' (sorry, thats a bit rude isn't it)..........

Oh, BTW, I think our 'National Grid' power lines run about 440 KV - thats a scary HV. Anyone want to stand under one on a damp day...........

I the dry, Electricity needs 1MV to jump 1m - lightning strikes are often in the GV range!!!!!!!, but in the wet it needs much less potential difference to jump a spark across a gap - hmmmm, thinking about those cracklin' HV lines........

[gpach]

Pinecone, I must admit I didnt realize how high the transmission lines run for voltage. Am use to more of an industrial in plant setting and the most we see coming in is 2500.

In regards to the high tension overhead lines. When I was a lot younger (many years ago) I use to dirt bike in the hills in BC. There were places under the HV lines that due to sag from pole to pole and the hills that the lines came closer (relatively) to the ground. I parked under them once and stoped to look around and listen to the noise of the transmission lines. When i went to start again, put my hands on the bars and got a mild shock. As I was poor my bike was older and the grips were worn on the end and when I touched each end of the handle bar I am assuming they were picking up enough field to give me a mild shock.

[Dynamic]

1.21 gigawatts is enough to travel back in time with a flux capacitor dontchaknow

[goldslinger]

I did lengthen the esc wire to the front of the heli on my JAZZ, there are no splices; I did it from the board, but I'm under 40 feet, so okay?

I maybe added 3 inches. I did it so I could turn the ESC around (I have it mounted under the battery tray on lower frame) so that the 3 wires to the motor could do a u turn from the front to go under and make a straight shot underneath the lower frame to the motor; nice and tidy.

Gary

[Pinecone]

I haven't heard of 440 KV, but it could be.

The 1 MV per m also is for non-ionized air. Get an ion path the voltage requirement goes down. Basis of a Jacob's ladder.

[chrisag]

KingKow,

I found a site that calculates the resistance of wire by length.
http://www.stealth316.com/2-wire-resistance.htm (http://www.stealth316.com/2-wire-resistance.htm)

Here is a site that lists the resistance of several connectors including Deans. It's in German but it has numbers.
http://www.elektromodellflug.de/hochstromst/hochstromstecker.htm (http://www.elektromodellflug.de/hochstromst/hochstromstecker.htm)

Three inches of 14 awg wire has a resistance of .0006 ohms. The problem becomes very complex because load varies, batteries vary, and everything changes with temperature. However, with a 2.1 ah source at 11.1 volts with a constant load for 6 minutes you would loose less than 1 second of flying time. Bottom-line don’t worry about wire length affecting flight time unless you start talking in terms of several feet of wire.

[MichaelJones]

Nikola Tesla was THE inventor of the alternating current power system. He developed these concepts independently of his employment by Westinghouse and his name alone appears on many of the patents pertaining to the production of alternating current and the alternating current motor and power transmission systems. Westinghouse was fortunate to have recognized Tesla's genius and we are all the beneficiaries. Even our radio systems owe a debt to Nikola for proving that power and information can be transmitted at a distance by alternating currents of high frequency. Tesla was a pioneer in radio transmission and was awarded precedent over Marconi for the invention in 1943 by the US Supreme Court.

History of Science buff.....and Heli addict. Now, who invented the Helicopter?

Mike

[KingKow]

KingKow,

I found a site that calculates the resistance of wire by length.
http://www.stealth316.com/2-wire-resistance.htm (http://www.stealth316.com/2-wire-resistance.htm)

Here is a site that lists the resistance of several connectors including Deans. It's in German but it has numbers.
http://www.elektromodellflug.de/hochstromst/hochstromstecker.htm (http://www.elektromodellflug.de/hochstromst/hochstromstecker.htm)

Three inches of 14 awg wire has a resistance of .0006 ohms. The problem becomes very complex because load varies, batteries vary, and everything changes with temperature. However, with a 2.1 ah source at 11.1 volts with a constant load for 6 minutes you would loose less than 1 second of flying time. Bottom-line don’t worry about wire length affecting flight time unless you start talking in terms of several feet of wire.
Thanks mate. As you said. nothing to worry about.

Cheers.

[Pinecone]

Again, nothing to worry about over resistance, but it can be a big deal due to inductance, with our pulsed use of power.

DO NOT EXTEND the leads between the battery and ESC, the increased length can cause damage to your ESC. If you have to extend, extend between ESC and motor.

Now, some ESC have very short leads, so extending to the equivalent length of other ESCs should be fine.

[TGibe]

Again, nothing to worry about over resistance, but it can be a big deal due to inductance, with our pulsed use of power.

DO NOT EXTEND the leads between the battery and ESC, the increased length can cause damage to your ESC. If you have to extend, extend between ESC and motor.

Now, some ESC have very short leads, so extending to the equivalent length of other ESCs should be fine.

Pinecone,

What total length is acceptable between ESC and battery?

For instance I lengthened the power cables on my TRex500 as the ones that came with it were very short... I am not sure what the length is currently, but this is being fed into my eagletree (the one with wire leads) whichs adds even more length....

Thanks,
Allen