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lizardmech

Melting wire solution?

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Posted (edited)

Helukabel Helutherm 400 should be good up to 400 degrees Celcius (450C for short term), and is available in sizes like 1.5mm2 (about 16-15AWG) and 2.5mm2 (about 13AWG) which should be close to the current cabling size, as well as in smaller and larger sizes. The minimum bending radius is about 15 times the cable diameter, which might cause problems...

http://www.tme.eu/en/Document/b5a01e37d893e323b7efb45b27a09bf5/K_029_HELUTHERM___400.pdf

http://www.tme.eu/en/details/hterm1x2.5/heat-resistant-cables/helukabel/50968/

 

 

Edited by esaj
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4 hours ago, lizardmech said:

Stumbled across this product on digikey, 600V 300 degree celcius  rating on this wire. You would have to resolder the motor but might be a useful short term fix that doesn't require the axle to be redesigned.

https://www.digikey.com/en/product-highlight/a/alpha-wire/thermothin-hook-up-wire

This wire has great temperature specs but Wow is it expensive! Maybe all of EUC can pitch in a purchase a roll together.:) It appears 16awg is the largest they offer.

W5CynMm.jpg

3 hours ago, esaj said:

Helukabel Helutherm 400 should be good up to 400 degrees Celcius (450C for short term), and is available in sizes like 1.5mm2 (about 16-15AWG) and 2.5mm2 (about 13AWG) which should be close to the current cabling size, as well as in smaller and larger sizes. The minimum bending radius is about 15 times the cable diameter, which might cause problems...

 

Definitely cheaper. What are your thoughts about GW using mismatched motor and mainboard wires? My thoughts are if they used the same 14 awg silicone wire that is soldered to the board for the motor wires exiting the axle shaft there would be less resistance = less heat. Unfortunately it is a very tight fit but doable. 

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1 minute ago, Rehab1 said:

This wire has great temperature specs but Wow is it expensive! Maybe all of EUC can pitch in a purchase a roll together.:) It appears 16awg is the largest they offer.

Definitely cheaper.

Actually, the Helukabel is more expensive at around $5/meter depending on size, a little less if ordering 50, 100 or more meters, in comparison the Alpha Wire's 16AWG is around $2.48/meter, it's just that the Alpha is sold in 1000-feet (304.8m) reel, whereas the minimum amounts TME sells the Helukabels' are 5 or 10 meters (depending on size), with the price dropping a bit going to higher amounts. Then again, TME doesn't have all the sizes listed in the PDF datasheet available, and it probably wouldn't make sense to order from Poland for the non-EU -riders. Couldn't find it (just a quick search) in Digikey, but probably there are US-based dealers too. Still, the bending diameter could be problematic, the datasheet says that it should be 15 times the diameter in minimum, and for example the 2.5mm2 (13AWG) has a total diameter of 3.4mm, making the minimum bending diameter around 51mm (about 2 inches).

 

1 minute ago, Rehab1 said:

What are your thoughts about GW using mismatched motor and mainboard wires? My thoughts are if they used the same 14 awg silicone wire that is soldered to the board for the motor wires exiting the axle shaft there would be less resistance = less heat. Unfortunately it is a very tight fit but doable. 

I think it's quite common (the Firewheel also had very tiny looking cables coming from the motor in comparison to those coming from the mainboard), although not wise for higher powered motors, those wires are going to carry a lot of current under hill climbing and such. But I'd expect them to be able to persuade the motor manufacturer to use thicker gauge, if they buy more motors..? Lowering the resistance produces less heat for the same amperage, so going thicker on the wiring would seem like a good idea, then there'd be no need to use special heat-resistant wiring ;) 

The PowerStream AWG-table ( https://www.powerstream.com/Wire_Size.htm ) has resistances for different cable thicknesses (although, they're calculated based on solid single-strand wire):

10AWG:  3.276392 milliohms per meter
12AWG:  5.20864 milliohms per meter
14AWG:  8.282 milliohms per meter
16AWG:  13.17248 milliohms per meter

Since the power lost over the wire is current squared times resistance (I2R), the power loss increases linearly with the resistance (for the same current). Looking at those values, when going 2 numbers "smaller" in AWG (like 10 -> 12AWG, or 14->16AWG), the power loss raises by about 60% each time! Depending on the actual current & wattage heating the wires, it might make a big difference or not be very meaningful...

 

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3 hours ago, esaj said:

Lowering the resistance produces less heat for the same amperage, so going thicker on the wiring would seem like a good idea, then there'd be no need to use special heat-resistant wiring ;) 

Unfortunately until they enlarge the axles and shaft to accept the larger wires that will not happen soon.

 

3 hours ago, esaj said:

The PowerStream AWG-table ( https://www.powerstream.com/Wire_Size.htm ) has resistances for different cable thicknesses (although, they're calculated based on solid single-strand wire):

That is a great wire size table and voltage drop calculator! One of the other tables depicts a huge difference between max amperage for chassis wiring and power transmission. Why the large discrepancy between the two?

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4 hours ago, Rehab1 said:

That is a great wire size table and voltage drop calculator! One of the other tables depicts a huge difference between max amperage for chassis wiring and power transmission. Why the large discrepancy between the two?

Those are more like "conservative" values, it's explained at the top of the page:

Definition: ampacity is the current carrying capability of a wire. In other words, how many amps can it transmit? The following chart is a guideline of ampacity or copper wire current carrying capacity following the Handbook of Electronic Tables and Formulas for American Wire Gauge. As you might guess, the rated ampacities are just a rule of thumb. In careful engineering the voltage drop, insulation temperature limit, thickness, thermal conductivity, and air convection and temperature should all be taken into account. The Maximum Amps for Power Transmission uses the 700 circular mils per amp rule, which is very very conservative. The Maximum Amps for Chassis Wiring is also a conservative rating, but is meant for wiring in air, and not in a bundle. For short lengths of wire, such as is used in battery packs you should trade off the resistance and load with size, weight, and flexibility. NOTE: For installations that need to conform to the National Electrical Code, you must use their guidelines. Contact your local electrician to find out what is legal! 

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Posted (edited)
On 7/9/2017 at 1:55 AM, esaj said:

Definition: ampacity is the current carrying capability of a wire. In other words, how many amps can it transmit.

I must be going to bed to early and missing posts. Sorry. How do you determine the amount of current (amps) that is being carried through the motor wires of an EUC at a given time?

My dilemma is what size bullet connector to use when  I reinstall the new board on the ACM. Castle is a superior bullet connector so I have selected it. The 4mm connectors are designed for 16 - 13 awg wires and can carry up to 75A each. The next size is 5.5 mm, which are arriving today, are designed for 10-12 awg wires and double the current capability to 150 amps. The problem is the recessed hole in the end of the bullet for the wire is way too large for the 14 awg. I would have to fill the hole with an over abundance of solder in order to encapsulate the wire adequately.  I'm not sure if this will add additional resistance to the connector.  Ideas?

 

 zO7sZh6.jpg

Edited by Rehab1
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31 minutes ago, Rehab1 said:

... The next size is 5.5 mm, which are arriving today, are designed for 10-12 awg wires and double the current capability to 150 amps. The problem is the recessed hole in the end of the bullet for the wire is way too large for the 14 awg. I would have to fill the hole with an over abundance of solder in order to encapsulate the wire adequately.  I'm not sure if this will add additional resistance to the connector.  Ideas?

You could maybe "fold" the bare 14 awg wire a couple of times, so the copper fills the hole of the bullet connector? Or "press" the awg 14 wire with an solid copper wire into the hole? (if this is then still reliable solderable and without destroying the threads of the awg14 ... )

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Maybe we should go the HI-FI route and replace our copper cables with silver?... :D

Though the difference is not massive, every little bit helps.

Mighty expensive wheels!

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Posted (edited)
57 minutes ago, Rehab1 said:

I must be going to bed to early and missing posts. Sorry. How do you determine the amount of current (amps) that is being carried through the motor wires of an EUC at a given time?

Without measuring, you don't, you could try estimating them based on the figures the wheel gives you, and then using an average, but the actual current changes a lot during riding depending on situation. Probably you could just go with a conservative value, like using a very low battery voltage and maximum peak power (4kW?), if the wiring should be able to handle that, you should have no issues with the wiring being inadequate at any point... 

3V per cell * 20 cells = 60V  (probably the wheel won't let you even ride it this empty)

The current needed to produce 4kW at 60V would be 4000W / 60V = 66.666... A .  The conservative value for 14AWG cable for chassis wiring is 32A, so roughly half of that. But, you won't be using 4kW of power constantly, or riding with depleted battery packs, and at higher voltages the current will be smaller. A more realistic scenario is likely that the average power you're using is typically way less than 1kW (probably a few hundred watts for riding a level road at steady speed, if that), and only goes up during acceleration and climbing. I'm not even sure if ACM/MSuper can peak up to 4kW.

"In careful engineering the voltage drop, insulation temperature limit, thickness, thermal conductivity, and air convection and temperature should all be taken into account."

Kinda hard without pretty good measurements or simulations of everything... just go as thick as possible? ;)

 

Quote

My dilemma is what size bullet connector to use when  I reinstall the new board on the ACM. Castle is a superior bullet connector so I have selected it. The 4mm connectors are designed for 16 - 13 awg wires and can carry up to 75A each. The next size is 5.5 mm, which are arriving today, are designed for 10-12 awg wires and double the current capability to 150 amps. The problem is the recessed hole in the end of the bullet for the wire is way too large for the 14 awg. I would have to fill the hole with an over abundance of solder in order to encapsulate the wire adequately.  I'm not sure if this will add additional resistance to the connector.  Ideas?

Adding more solder into the cup shouldn't raise the resistance, by the contrary, it should lower it, as there's more cross-sectional "path" for the current to travel through. Still, it might be tricky to solder, and you want as much as possible of "copper-to-copper" -contact to minimize resistance. Not that soldering tin's a really bad conductor either, but copper (and silver) are superior.

 

Material

Resistivity
p(Ω•m) at 20°C

Conductivity
σ(S/m) at 20°C

Silver 1.59x10-8 6.30x107
Copper 1.68x10-8 5.98x107
Annealed Copper 1.72x10-8 5.80x107
Gold 2.44x10-8 4.52x107
Aluminum 2.82x10-8 3.5x107
Calcium 3.36x10-8 2.82x107
Beryllium 4.00x10-8 2.500x107
Rhodium 4.49x10-8 2.23x107
Magnesium 4.66x10-8 2.15x107
Molybdenum 5.225x10-8 1.914x107
Iridium 5.289x10-8 1.891x107
Tungsten 5.49x10-8 1.82x107
Zinc 5.945x10-8 1.682x107
Cobalt 6.25x10-8 1.60x107
Cadmium 6.84x10-8 1.467
Nickel (electrolytic) 6.84x10-8 1.46x107
Ruthenium 7.595x10-8 1.31x107
Lithium 8.54x10-8 1.17x107
Iron 9.58x10-8 1.04x107
Platinum 1.06x10-7 9.44x106
Palladium 1.08x10-7 9.28x106
Tin 1.15x10-7 8.7x106
Selenium 1.197x10-7 8.35x106
Tantalum 1.24x10-7 8.06x106
Niobium 1.31x10-7 7.66x106
Steel (Cast) 1.61x10-7 6.21x106
Chromium 1.96x10-7 5.10x106
Lead 2.05x10-7 4.87x106

As you can see, silver & copper are actually superior to gold as a conductor, often you see connectors advertised with "gold-plated", they're actually higher resistance than copper or silver, but the point of gold plating seems to be the better corrosion resistance.

Edited by esaj
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26 minutes ago, Chriull said:

You could maybe "fold" the bare 14 awg wire a couple of times, so the copper fills the hole of the bullet connector? Or "press" the awg 14 wire with an solid copper wire into the hole? (if this is then still reliable solderable and without destroying the threads of the awg14 ... )

That's an idea! When the Castle 5.5s arrive today I will have a better idea. I could also  double up on the connectors and slide the 4mm into the 5.5mm.

If the amperage never exceeds 75 amps per motor wire then the 4mm would be sufficient. Sometimes bigger is not better.

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Posted (edited)
11 minutes ago, Rehab1 said:

That's an idea! When the Castle 5.5s arrive today I will have a better idea. I could also  double up on the connectors and slide the 4mm into the 5.5mm.

If the amperage never exceeds 75 amps per motor wire then the 4mm would be sufficient. Sometimes bigger is not better.

When the ampacity of a connector is defined, what would happen if the current momentarily gets above the defined number?

I kind of doubt there is more than 75A going through the connectors for very long, if for no other reason that we don't fry the isolation that often... But someone with a bit more knowledge of this might want to pipe in?

Edit: Aaaaaand, then I read the post right above and realised I should read before I ask questions :D

You would probably be good with 75A max...

Edited by Scatcat
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7 minutes ago, esaj said:

Kinda hard without pretty good measurements or simulations of everything... just go as thick as possible? ;)

Excellent info. Thanks! This comment really stood out. 

9 minutes ago, esaj said:

As you can see, silver & copper are actually superior to gold as a conductor, often you see connectors advertised with "gold-plated", they're actually higher resistance than copper or silver, but the point of gold plating seems to be the better corrosion resistance.

Silver is at the top of your list for conductivity. I do have silver solder but it requires a much higher temperature to become molten. I will experiment with it today. Thanks again! 

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Posted (edited)
38 minutes ago, Rehab1 said:

That's an idea! When the Castle 5.5s arrive today I will have a better idea. I could also  double up on the connectors and slide the 4mm into the 5.5mm.

If the amperage never exceeds 75 amps per motor wire then the 4mm would be sufficient. Sometimes bigger is not better.

Yes and no, using thicker/higher ampacity cable causes less power loss at the cable (less resistance = less voltage drop for same current vs. higher resistance), so the cables shouldn't then heat up as much. But of course especially in mass manufacturing, they won't use thicker wiring than is necessary, because copper ain't free and you can run into problems with space, bending radiuses for the wires and such.

 

30 minutes ago, Scatcat said:

When the ampacity of a connector is defined, what would happen if the current momentarily gets above the defined number?

Nothing, sort of. ;) The ampacities of the connectors are likely based on some (more or less theoretical?) model of the amount of power wasted as heat in the connector, and then they put a (conservative?) value on the connector at which it shouldn't heat "too much". Higher current will cause the connector to heat up more (I2 * R), then it's up to the specific heat capacity of the material (how many joules you need per gram of material to make it go up one Celcius degree) and the rate that heat flows off (radiates/conducts off from the connector) that can be used to determine where it will heat too much (like start to melt off plastic around the connector, if there is such). I don't know the specifics, probably there's a certain temperature (above ambient) that it's guaranteed to stay below at the maximum (continuous) current. I don't know if the values given in the connectors take into account power dissipation at soldered/crimped connections going to the connector ends.

Of course, if you go above the rated ampacity, there's a chance that the connector will heat enough to melt the plastics (or the wire sheathings nearby), even the metal, or welds itself. Over a short period, you're likely looking at hundreds or thousands of amperes though. Otherwise the connector might heat up a little bit over that short period, but then cools down again once the current drops lower, as the heat flows off / radiates into the surroundings.

I don't think this connector (and the nut, and the cable) were designed for this much power dissipation (here it's likely because of a bad contact, causing more resistance at the connection and heating up things through wasted power):

w11p9Ij.jpg

 

 

Quote

I kind of doubt there is more than 75A going through the connectors for very long, if for no other reason that we don't fry the isolation that often... But someone with a bit more knowledge of this might want to pipe in?

I think that @zlymex said that he's put 60A fuse in his Gotway (MSuper V3?) and it has never blown, although fuses will allow higher current for short periods (there are different "speed ratings" for fuses, like slow, fast, very fast, ie. how long and how much overcurrent they can pass before blowing), but at least on average it would seem it won't stay above 60A for long. 

Edited by esaj
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35 minutes ago, esaj said:

 

I don't think this connector (and the nut, and the cable) were designed for this much power dissipation (here it's likely because of a bad contact, causing more resistance at the connection and heating up things through wasted power):

w11p9Ij.jpg

 

 

 

Great picture.  Worth a thousand words as they say.  Where is it from and what is the application?

 

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Posted (edited)
17 minutes ago, Pard said:

Great picture.  Worth a thousand words as they say.  Where is it from and what is the application?

It's from imgur, the picture only had the title "rugged Russian LED indicates a slight overload":

http://imgur.com/gallery/YegLM

Could be some house mains, the copper bar might be neutral or one of the phases (or the phase, I don't know if they use 3- or 1-phase systems there). No idea also if it's really Russian, or someone just made up the topic. I first thought the nut glowing red hot was some sort of see-through plastic, but nope, apparently it's just a steel nut around 800 degrees Celcius :D

EDIT: There's the letter "N" on one of the cables going to the bar and the wires are blue, so likely it's the neutral. Not that it really matters ;)

Edited by esaj
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Just now, esaj said:

 "rugged Russian LED indicates a slight overload":

 

:roflmao:

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On 7/12/2017 at 5:32 AM, esaj said:

Yes and no, using thicker/higher ampacity cable causes less power loss at the cable (less resistance = less voltage drop for same current vs. higher resistance), so the cables shouldn't then heat up as much. But of course especially in mass manufacturing, they won't use thicker wiring than is necessary, because copper ain't free and you can run into problems with space, bending radiuses for the wires and such.

 

Nothing, sort of. ;) The ampacities of the connectors are likely based on some (more or less theoretical?) model of the amount of power wasted as heat in the connector, and then they put a (conservative?) value on the connector at which it shouldn't heat "too much". Higher current will cause the connector to heat up more (I2 * R), then it's up to the specific heat capacity of the material (how many joules you need per gram of material to make it go up one Celcius degree) and the rate that heat flows off (radiates/conducts off from the connector) that can be used to determine where it will heat too much (like start to melt off plastic around the connector, if there is such). I don't know the specifics, probably there's a certain temperature (above ambient) that it's guaranteed to stay below at the maximum (continuous) current. I don't know if the values given in the connectors take into account power dissipation at soldered/crimped connections going to the connector ends.

Of course, if you go above the rated ampacity, there's a chance that the connector will heat enough to melt the plastics (or the wire sheathings nearby), even the metal, or welds itself. Over a short period, you're likely looking at hundreds or thousands of amperes though. Otherwise the connector might heat up a little bit over that short period, but then cools down again once the current drops lower, as the heat flows off / radiates into the surroundings.

I don't think this connector (and the nut, and the cable) were designed for this much power dissipation (here it's likely because of a bad contact, causing more resistance at the connection and heating up things through wasted power):

w11p9Ij.jpg

 

 

I think that @zlymex said that he's put 60A fuse in his Gotway (MSuper V3?) and it has never blown, although fuses will allow higher current for short periods (there are different "speed ratings" for fuses, like slow, fast, very fast, ie. how long and how much overcurrent they can pass before blowing), but at least on average it would seem it won't stay above 60A for long. 

That picture is showing overload of bus. Look at the size of the cable compared to the little screw made is steel. 

The cable is pulling way too many amps for the connection type. Just like the bullet connectors. 

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