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Wire Gauge in Esk8

vesc

#1

I’m about to solder a bunch of things together and it occurred to me; I have 4 different wire gauges I’m using in my electrical setup and I haven’t thoroughly thought this through.

The forums I’ve reviewed in the RC world suggest that this would be alright, but I’d feel a lot more confident with some input from all of you!

In the pic there are the 4 different wire gauges in my build. The 16AWG serial adapter seems like the most likely bottleneck; but I think 16AWG is able to handle the draw from an 8S battery to a 245Kv motor. Does that sound right?

Other info about the build: Enertion VESC, 14T/40T, 127mm pneumatic wheels


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#2

In any electrical system you are only as good as your weakest link.
in your case its the 16AWG joiner. which according to the chart below is good for 35Amps
Personaly I’d use a minimum of 12AWG throughout.


#3

I use 10 gauge silicone wire on everything unless I’m trying to preserve a particular component for a possible return if it fails. 10 guage silicone and 5.5mm bullet connectors on both sides of the ESC.

But i think what you’ll find typical is 10 gauge between the battery and ESC and 12 gauge between the ESC and the motors. I’m pretty sure that Enertion is the only vendor putting 10 gauge silicone leads on the motors with 5.5mm bullets. Most motors we use have 12 guage non-silicone leads which i would then replace with 10 gauge silicone.

However, I’d be shocked if I saw any performance difference at all between a completely 12 gauge wiring harness and a 10 gauge harness at 6S. Maybe at 8S or 10S you might see a difference in heat or load handling or something. In fact I’m considering going completely 12 gauge in my 6S system because it will help eliminate some of the spaghetti monster as well as shed a few grams of metal.


#4

Thanks @lowGuido , I’m going to toss the serial adapter I have and make a new one using 12AWG silicone wire. I’ll use the remaining 12AWG wire for the rest of the connections, and solder that onto my VESC.


#5

Thanks @longhairedboy - Your response begs another question; does everyone replace their motor wires if they buy a “hobby” motor (i.e. one that isn’t from @onloop or @torqueboards ?) I have an SK3 and truthfully, the wire coming out of it looks flimsy. I thought I would just have to live with it because I wasn’t aware that motor wire is replaceable.

Can I just snip the leads that extend from the motor and then solder on the 10AWG, or do you suggest that I dismantle it and replace the wire from its source?

This forum rocks! Thanks everyone!


#6

you can “replace” the motor wires, I have done it before. but it is a little painful.
because the “leads” coming from the motor are actually a group of intertwined single strand windings of the stator they are the source, so to speak. and all the strands are individually insulated from each other.
so if you do decide to cut the leads and replace them you will need to scratch the insulator off each strand first.

I have had a little success with dipping the ends in acetone before soldering, but it was painful and potentially dangerous.

edit: in case I haven’t been clear… don’t do this. its not worth the effort for the little (if any) reward.


#7

Yikes! Thanks @lowGuido. I think that I’ll skip this step in my first build. I’ll just use the wire and connectors that came from the factory on the SK3.


#8

I have used seven SK3’s in my builds and I have always used the stock leads and connectors. never had a problem with them


#9

I didn’t go all the way into the stator with these though. I cut the leads at about 1/2" past the casing and butt-soldered the silicone leads on at that point, then heat shrinked everything together nicely.

The main reason i did this was because the silicone wire is flexible and springy, which is what you need in this application. Not because i needed a higher gauge wire at the motor. The leads on the motor are properly rated for what the motor can accept already.


#10

Great to know @lowGuido! Thx again!


#11

I can see an issue with the drive train.

Drive pulley 14
Driven pulley 40
Nominal Battery voltage approx 30
Motor [kV] 245
Tire diameter [mm] 127
Final ratio 2.86
Engine revolution 7350 rpm
Top speed 62 km/h

This top speed is too high. You will not have enough torque. Especially with pneumatic tyres. I think the motors will overheat and may suffer an early death.

You should aim for max torque with pneumatic.

I suggest gearing for top speed of 35km.

Which means you need a wheel pulley around 70 teeth.

However the problem with that size pulley it is not much smaller then the wheel and very close to the ground and debris.

After testing several variations I ultimately had to go with 3mm pitch pulleys at 15mm wide so i could achieve an appropriate reduction whilst maximising pulley/ground clearance.


#12

Thanks for thinking this through @onloop. I’ve been wondering the same thing; there’s a 60T wheel pulley available for the pneumatic wheel I’ve got, it’s 5mm pitch and 9mm wide; probably not optimal, but I think it would accomplish a better gearing. Does that sound like it’d solve this problem?

When I selected the drivetrain, I based it on @psychotiller’s pneumatic build posted here that featured a 245Kv motor, 6-inch pneumatics (opposed to my 5-inch), 14T/40T gearing, and 8S. @psychotiller, maybe you could weigh in on your experience with that build?

Thanks again, so glad to have everyone’s input!


#13

12AWG is relatively smaller
10AWG is not too bad
8AWG is even thicker.

Depends on how much amps you are pulling at what area.
Ex. 8AWG wire to your UBEC would be pointless.

I think 10AWG is a happy medium for all wiring since it’s still relatively small. You can run 8AWG if you plan on running higher amps but it’s not recommended since higher amps = more heat.

Onloop makes the motor wires like that since 5.5mm bullet connectors don’t come undone like 4mm bullets tend to do. You also can’t space out the 4mm male connectors like you can for a 5.5mm male connector.

He uses the 10awg wire to allow the wire to have more flexibility.

It’s over spec’ed but doesn’t hurt it either. Great idea…

Motors will only deliver 30-80 amps a piece which is rated for like 14AWG wire or something and by default they are usually all 12 awg.

@treenutter - You don’t need to replace your motor wires, just don’t stress the motor wires and/or if they are being stressed run an extension wire so the wire that flexes is the extension wire and not the actual motor wire.

I find the SK3 motor wires very strong and rigid which is a good thing IMO. You just need to run an extension.


Blank Custom | SK3 192KV | VESC | 9S LiPo | Custom Mount kit | Caliber Raw 44s | 83mm | GT2B Mod Sparkle
#14

When I built my pneumatic, I knew with 150mm wheels i’d be pushing the motor. I can bust 40mph on that board, but it does have some grunt too. it hasn’t stalled out on any hills I’ve tried yet. It’s a very smooth board to ride. Get the 60 and if you don’t like the 40 switch it out. Easy enough.


#15

Thanks @psychotiller … 40mph sounds scary! I’ll start off with the 60T and see how it goes.


Cable Porn! Ohhhhh yeahhhh
#16

Thx @torqueboards I’ll keep an eye on the motor wires over time, if they look like they’re aging prematurely l’ll replace then with more flexible silicone wires.


#17

In summary, the way to select wire gauge is to compare the power-handling limits of your wires and connectors with the maximum current your motor can draw.

In my case, the motor has a max 70A draw. 12AWG wire can handle up to 84.40A, so 12AWG would be the minimum wire gauge to use, just as @lowGuido suggested. Heavier wire (10AWG) would provide further overhead.

That just leaves the issue of connectors! So far I’ve been using Deans connectors. Although Dean’s doesn’t publish an official rating, I read lots of reports of folks pulling 100A with no issues. However, these reports are from the RC world, where the duration of a usage session is about 10-20 minutes (much lower than our typical esk8 application). I like Deans because they’re small and they seem capable of the draw. I also have a bag of them so I’ve been practicing my soldering!

Does anyone have experience with Deans (good or bad)?


#18

I think deans are ok. Evolve uses deans and I think I seen a few other decks use Deans. Deans seem like the connected would come off easily. Personally, I like 5.5mm bullets, EC5 or XT90 connectors. The cost isn’t much so I’d go for something better. I also think Deans are easier to short on accident.


#19

i prefer bullet connectors because they are a simple butt-joint type connector that can be easily taped or heat shrinked together without taking up any more space in the box than the wire itself. The 4mm for the 12 gauge and the 5.5mm for the 10 gauge wires are basically the only connectors you need in a build. Oh and they’re dirt cheap and come by the bag.

The only disadvantage to using them is the occasional arcing, sparking, and possibly even slag splattering that happens when the battery leads touch each other, but as long as you tape them up during the disconnect process that’s a non-issue. Once after accidentally allowing the leads to come in contact with each other i found myself looking down at a shirt covered in molten metal. The connector had literally melted and sprayed onto my shirt much like welding slag. Good times.


#20

@longhairedboy I can certainly appreciate the space-saving and ease of bullet connectors! As I’ve been planning out my enclosure I see all kinds opportunities to reduce wasted space; connectors and extra wires are the major culprits my case. I think I’ll have quite a spaghetti monster by the end! I’m not as experienced as you are; not sure I trust myself to remember to keep battery leads from making contact!