Is using thick silicone wire a waste of money?

[EdwardNY]

In my 48volt setup I used 10AWG wire throughout. I think that was a huge waste.
Here are the Continuous amp ratings for different wires

20AWG 15 Amps
18AWG 20 Amps
16AWG 35Amps
14AWG 60 Amps
12AWG 90 Amps
10AWG 150 Amps
8AWG 200 Amps

I would say that on a 48volt 30Amps setup that I use. Having 12s4p setup, it should only draw from each paralleled batteries about 8 amps each at the max.
This means I should get away with the main battery line being 16AWG, and the wires connecting the different batteries 20AWG and I would never go over the rated amps usage from the batteries. Remember those are continuous ratings so most likely it can handle a higher peak, also you most likely will never be drawing the max amp from the batteries so most of the time you will be far below a 30 amp draw.

Say you have a higher end setup and are drawing 100 amps. In a 4p setup (max draw 25amps from each paralleled batteries) you should be able to get away with 16AWG wires connecting your parralel packs and have a 10AWG (probably be OK with 12AWG wire) wire as your main battery wire.

I know from various hobbies that people like to go overboard with things. Like computer cooling etc., When it seems that it is mostly a waste. SInce I am using 10AWG wire for my complete 12s4p setup, that was a total waste of money and space inside my battery bag to use such heavy wires. Not only was it a waste but soldering those 10AWG wires into small connectors was a big pain, especially considering 4mm bullet connectors do not fit over 10AWG wire.
You may say that well, it is not much more money etc. But I would have easily made my parallel harness double the size to make it easier to connect my batteries if I was using much cheaper and smaller AWG wire.

I would like to know what people think about this and if the reality of it is that most people waste money on oversizing the AWG wire as they really do not need to.

 

[hydro-one]

I think your wires are melting and you have been sniffing the fumes!!!

Just kidding man , but there is no way those numbers are right!! the amp ratings i mean

 

[EdwardNY]

I think your wires are melting and you have been sniffing the fumes!!!

Just kidding man , but there is no way those numbers are right!!

Those numbers are correct. I think people really underestimate the amp draw and the size of the wires needed to carry that amp draw.


I would like to see if someone can disprove those numbers though. Maybe I am overlooking something.

I got the continuous amp draw from EPbuddy.com. Take a look at any of their silicone wire. It says Continuous current safe. Also, this is silicone wire, they can take lots of heat. I mean, think about how much we heat those up soldering our connections without any problems.

 

[dnmun]

but the heat is from the energy lost to the resistance of the wire. but you asked if you really need to use the silicone wire. that is a different question. it is useful because it is so flexible. which is why people use it. you should stick to 12AWG up to 40A.

 

[Farfle]

The leads coming out of batteries are big overkill for most ebike use when paralleled several times (assuming turnigy packs with 10/12Awg leads). They could stand to be smaller.

 

[Punx0r]

Those numbers are correct. I think people really underestimate the amp draw and the size of the wires needed to carry that amp draw.


I would like to see if someone can disprove those numbers though. Maybe I am overlooking something.

I got the continuous amp draw from EPbuddy.com. Take a look at any of their silicone wire. It says Continuous current safe.

They're talking shit.

If you want your 200*C rated cable to actually be at 200*C in use then by all means use their numbers

Just Google something like "AWG current rating" to see dozens of data tables with more realistic, industrial ratings.

 

[itchynackers]

Didn't LFP test a 10awg wire at 50a? If I remember correctly, it began to smell.

 

[bigmoose]

Here is a screen shot of my XLS file that I keep on wire and such. It should contain the information you need. The quoted ampacities are theoretical for the wire at 200 degC. Not a suitable design condiditon IMHO.

 

[liveforphysics]

Here are the Continuous amp ratings for different wires

20AWG 15 Amps
18AWG 20 Amps
16AWG 35Amps
14AWG 60 Amps
12AWG 90 Amps
10AWG 150 Amps
8AWG 200 Amps

Whoa! They must do all there testing in liquid nitrogen or something. lol Most of those numbers are roughly 4x too high.

I've had 4awg melt it's insulation off at 150amps. 90amps for 12awg? It's going to be glowing red. Most 10awg is on fire in under 2 minutes with 100amps constant going through it. 200amps for 8awg??? Holychit batman! I want what they are smokin!

 

[Eascen]

Okay: Voltage matters when it comes to amperage going over these wires, as well as length of the run. Those numbers might be safe for a 3" run, but I personally wouldn't trust them. I have 14 gauge wiring in my house (as most likely everyone here does) for a 15 amp breaker, and 12 gauge for 20 amp...

 

[redstone02]

If you want your 200*C rated cable to actually be at 200*C in use then by all means use their numbers

Just Google something like "AWG current rating" to see dozens of data tables with more realistic, industrial ratings.

+1 real $hit.
Not only should you think about wire insulation, include terminations, termination shrouds, and everything else along the circuit.
200C being conducted wonderfully via copper to you controller.
If you want heater for your legs, use those ratings.

 

[liveforphysics]

Okay: Voltage matters when it comes to amperage going over these wires, as well as length of the run. Those numbers might be safe for a 3" run, but I personally wouldn't trust them. I have 14 gauge wiring in my house (as most likelyr a 15 amp breaker, and 12 gauge for 20 amp...

Nope. Voltage matters zero for a wires current handling. The reason you see it on charts for braindead folks is becsuse they have an acceptable percentage of energy they deem OK to waste.

Length only plays a factor again if you have some limit set as an acceptable amount of power to waste in cabling, or in the event its a very short piece with substantial heatsinking from each connected end. Like the element in a fuse for example.

A system will continue to increase in temp as long as the heat added to the system exceeds the rate heat is shed from the system. If you have a 10ft wire at some current, say 50amps, and you have a 10000ft piece of thst wire at the same 50amps, the 10,000ft piece will have 1000 times more voltage drop across it, and hence 1000 times more power wasted heating it, but it also has 1000x more ability to disipate that energy its getting (unless its just in a coil or something where the heat from adjectent loops of wire are close enough to be heating eachother).

 

[amberwolf]

Here are the Continuous amp ratings for different wires

20AWG 15 Amps
18AWG 20 Amps
16AWG 35Amps
14AWG 60 Amps
12AWG 90 Amps
10AWG 150 Amps
8AWG 200 Amps

I see a fire in the future of whoever is using that chart as a guide.

 

[Eascen]

Okay: Voltage matters when it comes to amperage going over these wires, as well as length of the run. Those numbers might be safe for a 3" run, but I personally wouldn't trust them. I have 14 gauge wiring in my house (as most likelyr a 15 amp breaker, and 12 gauge for 20 amp...

Nope. Voltage matters zero for a wires current handling. The reason you see it on charts for braindead folks is becsuse they have an acceptable percentage of energy they deem OK to waste.

Length only plays a factor again if you have some limit set as an acceptable amount of power to waste in cabling, or in the event its a very short piece with substantial heatsinking from each connected end. Like the element in a fuse for example.

A system will continue to increase in temp as long as the heat added to the system exceeds the rate heat is shed from the system. If you have a 10ft wire at some current, say 50amps, and you have a 10000ft piece of thst wire at the same 50amps, the 10,000ft piece will have 1000 times more voltage drop across it, and hence 1000 times more power wasted heating it, but it also has 1000x more ability to disipate that energy its getting (unless its just in a coil or something where the heat from adjectent loops of wire are close enough to be heating eachother).

Thanks for the clarification, I was simply going by the housing wiring code requirements I'm used to. When I ran the new wires for my oven, because the run was longer than 20' I ended up with 6awg instead of 8, but after a bit more research it appears that's due to the voltage drop which makes complete sense. While I have someone on the subject, it's my understanding that the resistance = voltage/current, lowering the loss across a given medium (which is why power lines run in the kv range). Am I completely off base?

 

[mvly]

Maybe those numbers are for ultra short wires open into moving ambient 25 degree C temperature?

I run 30A through my 14G wires all day without problems. But the moment I put them in the bag, it start heating up fast. These are 200 degree C silicone wires from HK.

 

[liveforphysics]

I made this test lead to do a little experiment.

At 60amps and 90amps. At 60amps, it seemed to stabilize at around 208-212degC in ambient temp air. That's hot enough to melt a solder joint made with standard electronics solder (40/60 or 37/63 etc).

[youtube]pLHKh1zxze0[/youtube]

 

[TMaster]

Great video!

I always go here to get continuous amp ratings for wires: then I add a little more for silicone
http://www.powerstream.com/Wire_Size.htm (scroll down to table)

 

[liveforphysics]

Great video!

I always go here to get continuous amp ratings for wires:
http://www.powerstream.com/Wire_Size.htm (scroll down to table)

Yep, that chart is fair (the chassis wiring numbers seem slightly aggressive if you don't want your wires being flesh-cooking hot in continuous duty, but unlikely to be failing good wire insulation) and matches up with my own testing and experiences pretty well.

 

[recumbent]

The wires on my 7 foot long bike is 12ga, and the controller is rated at 35 amps, after a few years like this it only warmed-up a tad after a long grind up a steep hill wide open. But it was also a hot day so it may have been the sun and black wire combo soaking.

But the 45 amp Anderson connectors and the 16ga wire exiting the 9c motor spindle were definately very warm but not hot. The bike CA was reading more than 1500 watts continuously for 5 minutes.

So from my experience 12 ga wire is safe for ebikes with 35 amp controllers for sure.

 

[Eascen]

I made this test lead to do a little experiment.

At 60amps and 90amps. At 60amps, it seemed to stabilize at around 208-212degC in ambient temp air. That's hot enough to melt a solder joint made with standard electronics solder (40/60 or 37/63 etc).

Epic, thank you sir!

 

[Punx0r]

I was simply going by the housing wiring code requirements I'm used to. When I ran the new wires for my oven, because the run was longer than 20' I ended up with 6awg instead of 8, but after a bit more research it appears that's due to the voltage drop which makes complete sense. While I have someone on the subject, it's my understanding that the resistance = voltage/current, lowering the loss across a given medium (which is why power lines run in the kv range). Am I completely off base?

House wiring it likely more conservative (higher factor of safety) as the wiring can be buried in walls/insulation and the consequences of failure can be catastrophic.

If you need to transmit a given power then high voltage/low current means less losses (losses are I^2R). If you're pushing a given current thought it doesn't matter if it's at 10V or 100V. Only current and (wire) resistance matter.

 

[Stevesie]

Surely that table is of little use in this context without specifying length and acceptable voltage drop/power wasted as heat?

 

[John in CR]

The bigger the wire the better. Screw losing power and voltage drop just because of the wire. I use thick stuff already, but my next build gets some wire for welding leads I was eyeballing at the hardware store the other day. Six phase wires (its a 6 phase motor) and 2+2 for the battery mains will make for some interesting cable routing. If I can arrange them neatly and balanced, then maybe make them a focal point on the bike. Gotta keep them short though so as not to add too much weight in overkill, but like clamping dropouts there's really not such thing as overkill. That's even more true with wiring, since extra thickness always reduces resistance.

John