What is the max amps for different awg wire sizes?

[silviasol]

This is for the build I have linked in my signature. It is really cramped in the pan and for better flexibility of the wiring I want to redo it with smaller wire then the 12 awg I have been using. The main lines will be 12awg but inside the pack I have wires that would need 15amp max draw and 30 amp max draw. Is there a chart online somewhere that shows the max amp draw for different awg sizes?

 

[ridethelightning]

good stuff to know..

 

[Frank]

Yes. Do a search. It sounds like you are paralleling two strings, perhaps you could join them outside the pan (whatever that is, I cannot see your Sig. line on my tablet.)

 

[major]

..... Is there a chart online somewhere that shows the max amp draw for different awg sizes?

Do a google search (images) for Ampacity, Ampacity chart, Ampacity table, Ampacity of wire, etc. There are thousands of hits. The actual values may vary depending on the type of wire and how warm you allow it. It can boil down to a trade off. Loss (Watts) or voltage drop vs ease of packaging. You should also be able to find the resistance per unit length of the different wire gauges. With that and the length of the wires, calculate the resistance. Then Ohm's Law will tell you the voltage drop at a specific current draw. Judge that against the system voltage.

 

[Russell]

Here's one;

http://www.batteryspace.com/wirescables.aspx

-R

 

[bigmoose]

Here is a screen shot off of my Excel spread sheet for sizing wires. Google for code compliance information. I parallel strands all the time to up the ampacity of the run.

When you size the wire you are determining the amount of power you are willing to "loose" in the cable as I^2 * R heating losses. In the extreme that heating will play into the insulation capability at temperature. You can upgrade the insulation, and run the wire hotter... but you are increasing losses in that wire run.

 

[silviasol]

Good info! Going to order some 14awg to 22awg stuff.

..... Is there a chart online somewhere that shows the max amp draw for different awg sizes?

Do a google search (images) for Ampacity, Ampacity chart, Ampacity table, Ampacity of wire, etc. There are thousands of hits. The actual values may vary depending on the type of wire and how warm you allow it. It can boil down to a trade off. Loss (Watts) or voltage drop vs ease of packaging. You should also be able to find the resistance per unit length of the different wire gauges. With that and the length of the wires, calculate the resistance. Then Ohm's Law will tell you the voltage drop at a specific current draw. Judge that against the system voltage.

Ok so it also depends on the wire length, hmm. Most of the wiring I need is 3" or less to parallel the cells. Sounds hard to calculate though, I will try!

 

[dnmun]

i had to use 10AWG stranded to get my big 100A gel VRLA batteries back into my ZENN car in a different arrangement.

i was averaging about 80A and then had some 134A peaks and the wires did not get hot. but i had a wattmeter with 12AWG stranded for leads and the solder melted on the shunt from overheating and the 12AWG wire pulled out of the wattmeter when it melted.

 

[silviasol]

i had to use 10AWG stranded to get my big 100A gel VRLA batteries back into my ZENN car in a different arrangement.

i was averaging about 80A and then had some 134A peaks and the wires did not get hot. but i had a wattmeter with 12AWG stranded for leads and the solder melted on the shunt from overheating and the 12AWG wire pulled out of the wattmeter when it melted.

So you are saying there is a big difference in the max amps of 10awg then 12awg?

 

[Hillhater]

Somewhere in this discussion there should be a reference to the wire material (copper presumably) quality, purity etc.
There is some crap chinese wire around if you are not careful.
Terminations, solder joints etc also need some thought for higher current.

 

[John in CR]

So you are saying there is a big difference in the max amps of 10awg then 12awg?

12awg has over 50% more resistance. That's big to me.

To me anything higher than a pedelec type power ebike should use the largest practical wire gauge. When you skimp a shoot for the minimum wire gauge, then heat related failures in the wiring become pretty common around here. When you look at the maximum current listed on wire gauge charts like the one BigMoose shared or the one here http://www.powerstream.com/Wire_Size.htm it becomes apparent why ES members have so many wire related failures. This is especially true once you consider that while a controller may be rated as say a 40A controller, that's on the battery side, but the phase wires can easily see 80-100A due to phase current multiplication that occurs with PWM.

The flip side of that is that our bikes move through the wind, so we typically have good air flow available to use to help keep wire temps down, so the max amps for chassis wiring or power transmission don't necessarily apply.

 

[silviasol]

Somewhere in this discussion there should be a reference to the wire material (copper presumably) quality, purity etc.
There is some crap chinese wire around if you are not careful.
Terminations, solder joints etc also need some thought for higher current.

I am using silver solder with flux making sure the solder goes about 1/4" into the silicone tube and more then enough to cover the wire at the terminals.

To me anything higher than a pedelec type power ebike should use the largest practical wire gauge. When you skimp a shoot for the minimum wire gauge, then heat related failures in the wiring become pretty common around here. When you look at the maximum current listed on wire gauge charts like the one BigMoose shared or the one here http://www.powerstream.com/Wire_Size.htm it becomes apparent why ES members have so many wire related failures. This is especially true once you consider that while a controller may be rated as say a 40A controller, that's on the battery side, but the phase wires can easily see 80-100A due to phase current multiplication that occurs with PWM.

The flip side of that is that our bikes move through the wind, so we typically have good air flow available to use to help keep wire temps down, so the max amps for chassis wiring or power transmission don't necessarily apply.

Phase wiring, that is on a brushless motor? I have brushed.

 

[dnmun]

you should not have to worry too much about impurities in copper wire. copper has to be very pure and that level is easily achieved in order for it to be worked by pulling it through the die to make wire.

solder has 5-8 times the resistance of copper. hi temp solder is the worst, use lead solder if you can. brass has much higher resistance but it cannot be worked because it is not pure copper.

if you looked inside the lipo pack or inside the lipo can you would see tiny tiny surfaces that are the internal contacts between the cells of the battery. imagine two fingernails touching tip to tip. that is how the 20C of the 5Ah packs is carried through the pack.

then add on the 12" of wire between each pack and the contact resistance of the little connectors, about 5mR/pack so if you have 6 of these 4S packs to make a 24S lipo pack then you are carrying about 30mR of contact and connector wire resistance to each battery.

push 100A through it and you get 3V of voltage drop in the contacts and wires inside the battery. keep it to 30A and you only have 1V or about 1% voltage sag from the current, in the contacts only. add in the resistance of the tiny contacts between pouches and you lose another 1-2% from the true voltage expressed on each pack.

so you are already looking at about 2-3% sag just from the current flowing through the contacts inside the battery.

i have no concerns about using 12AWG for my battery leads but i only expect to see a maximum of 80A current and usually around 40A which the 12AWG can manage with not any heating at all. 10AWG should handle up to about 120A without much heating either imo.

the current induced heating is inside the battery packs. that is where the wires are tiniest and the amount of solder or crimp used to make the contact is the least.

 

[silviasol]

solder has 5-8 times the resistance of copper. hi temp solder is the worst, use lead solder if you can. brass has much higher resistance but it cannot be worked because it is not pure copper.

then add on the 12" of wire between each pack and the contact resistance of the little connectors, about 5mR/pack so if you have 6 of these 4S packs to make a 24S lipo pack then you are carrying about 30mR of contact and connector wire resistance to each battery.

push 100A through it and you get 3V of voltage drop in the contacts and wires inside the battery. keep it to 30A and you only have 1V or about 1% voltage sag from the current, in the contacts only. add in the resistance of the tiny contacts between pouches and you lose another 1-2% from the true voltage expressed on each pack.

so you are already looking at about 2-3% sag just from the current flowing through the contacts inside the battery.

Ouch, leaded solder is my worst enemy. I have went thru like 5 tips from oxidation using leaded solder, now using unleaded I have the same two tips, large tip and small tip, I have used for over 6 months. I think the new hakko stuff(blue/yellow colored equipment and they say "blue and yellow make green" as their slogan) is meant to perform best with leaded solder. I am only running 1c to maybe 1.15c with my 40ah pack, should I be concerned with any extra resistance of solder/wiring? Is resistance just an enemy for high voltage/high drain applications?

 

[dnmun]

with solder, you want the minimal thickness between the two conductors you are making the contact with and the maximum surface area wet by the solder between them in order to keep the contact resistance low.

the current flows in the cooper so the quicker it gets through the solder to the copper then that is the best. metal to metal contact of the conductors is the ideal. so crimp the ring terminals, butt solder wires by pushing their strands together so they intertwine at the joint to make the best linear connection.

my 40W soldering iron is so corroded it has a cup on the end, not a tip. but it is useful because the way i have to solder the battery pack leads, balancing leads between packs and the sense wires as well as the serial connections, the cup allows me to hold several wires together under the tip as i add a new wire to the pile at the connection without the wires squirting out of the stack when the solder melts.

 

[silviasol]

with solder, you want the minimal thickness between the two conductors you are making the contact with and the maximum surface area wet by the solder between them in order to keep the contact resistance low.

the current flows in the cooper so the quicker it gets through the solder to the copper then that is the best. metal to metal contact of the conductors is the ideal. so crimp the ring terminals, butt solder wires by pushing their strands together so they intertwine at the joint to make the best linear connection.

my 40W soldering iron is so corroded it has a cup on the end, not a tip. but it is useful because the way i have to solder the battery pack leads, balancing leads between packs and the sense wires as well as the serial connections, the cup allows me to hold several wires together under the tip as i add a new wire to the pile at the connection without the wires squirting out of the stack when the solder melts.

OK. What I had been doing is pressing the wiring down with a dull exacto knife while melting then allowing the solder to harden. This would make a difference for amp draw only? Will it matter with the balance leads?

 

[dnmun]

your balancing leads should see very low current unless you use the BC168 type charger.

50A continuous on 12AWG gets hot, but slowly. 10AWG will get hot at the 100A level too, but slowly. if you wanna keep the voltage drop low on a long run of wire then use a large enuff gauge to make it low. i use what i have available usually.

 

[liveforphysics]

Whenever it's possible to use a properly cold-forged crimped joint that causes the metals to flow together, do so.

Likewise, to answer your question, even the smallest wire can handle greater than millions of amps for extremely short duration pulses provided it's mechanically constrained in a way that prevents the magnetic fields induced by the current pulse from shredding the wire. However, even when the wire does shred, the plasma from the locally ionized gasses is also capable of millions, if not billions of amps of current transfer (think about a lightning bolt).

I made a magnetic pulse can shrinker for fun a few months ago. I'm using a few foot long piece of 10awg coiled up as the work coil. It seems to be undamaged with a calculated current >50,000A when connected through the spark gap to the 60,000kV pulse discharge capacitors.

If you wish to know the practical continuous current for an ebike application, use the brilliant table Bigmoose was so kind to provide.

 

[silviasol]

Whenever it's possible to use a properly cold-forged crimped joint that causes the metals to flow together, do so.

Likewise, to answer your question, even the smallest wire can handle greater than millions of amps for extremely short duration pulses provided it's mechanically constrained in a way that prevents the magnetic fields induced by the current pulse from shredding the wire. However, even when the wire does shred, the plasma from the locally ionized gasses is also capable of millions, if not billions of amps of current transfer (think about a lightning bolt).

I made a magnetic pulse can shrinker for fun a few months ago. I'm using a few foot long piece of 10awg coiled up as the work coil. It seems to be undamaged with a calculated current >50,000A when connected through the spark gap to the 60,000kV pulse discharge capacitors.

If you wish to know the practical continuous current for an ebike application, use the brilliant table Bigmoose was so kind to provide.

Thanks. I have a whole lot on info to look into now. Was thinking with my 18650 build I will do next I could use wiring to create an amp limit type setup to keep the controller/motor from drawing more the amps I want. Say I have the correct type wiring(sustains the extra heat without damage overtime) that allows only a certain amount of amps thru along with some amp circuit breakers set at the max c rating the pack can handle. With a powerful motor would it then accelerate without having too much torque and get to top speed at the desired rate I want? This way of course would keep the batteries within their amp ratings and keep them healthy. Is this a win win setup or are there disadvantages like loss of energy?

 

[Arlo1]

Whenever it's possible to use a properly cold-forged crimped joint that causes the metals to flow together, do so.

Likewise, to answer your question, even the smallest wire can handle greater than millions of amps for extremely short duration pulses provided it's mechanically constrained in a way that prevents the magnetic fields induced by the current pulse from shredding the wire. However, even when the wire does shred, the plasma from the locally ionized gasses is also capable of millions, if not billions of amps of current transfer (think about a lightning bolt).

I made a magnetic pulse can shrinker for fun a few months ago. I'm using a few foot long piece of 10awg coiled up as the work coil. It seems to be undamaged with a calculated current >50,000A when connected through the spark gap to the 60,000kV pulse discharge capacitors.

If you wish to know the practical continuous current for an ebike application, use the brilliant table Bigmoose was so kind to provide.

I for got to see your handy work from this.