Wire size for 1200W?

8 posts / 0 new
Last post
mf70
Offline
Last seen: 6 years 1 month ago
Joined: Friday, December 1, 2006 - 09:01
Points: 712
Wire size for 1200W?

I've been looking at my well-mauled Yonkang Crown scoot "Hummer". I've got about 3000Km on it; the odo went out at 2400K.

It has a nominal 700W brushed motor that actually draws about 20A measured at full throttle, or about 1200W. The odd thing is that the wire from the controller to the hub is 14GA! In fact, after pulling up a long hill, the wires will be detectably warm.

Would upping the connection to 10GA, say, increase efficiency and potentially range, or would it open the door to melting the windings? (I.E. is the 3 feet of 14ga wire acting as a current limiter?) According to a DC motor rebuilder, the discoloration on the comm that I'm seeing is from overloading it already.

I had a look at the wire resistance table linked in the "Wiring brushless Etek, cable guage?" thread, but they don't go small enough for me.

MF

strawhistle
Offline
Last seen: 8 years 2 weeks ago
Joined: Monday, March 10, 2008 - 08:43
Points: 340
Re: Wire size for 1200W?

:?
For wire sizes , it goes by AMPS at any voltage !! 14g = 15A 12g =20A 10g = 30a 8g =40A 6g =55 to 75 depending on the type of outer insulation If the max Amps to the motor is 20A then 20g wire with thhn coating (90degree ) will work for you , 10g would be called monster cable

thank GOD I wake up above ground !!!!

LinkOfHyrule
LinkOfHyrule's picture
Offline
Last seen: 14 years 9 months ago
Joined: Wednesday, October 17, 2007 - 14:54
Points: 730
Re: Wire size for 1200W?

Hmm, lets see:

14AWG wire has a resistance of 0.00297Ω/ft. You say there is 3 feet of wire between the batts and the motor, so I'm assuming a 6ft round trip. Since heat = current^2 * resistance, then you're losing 20A^2 * 0.00297Ω(6ft) = 7.128W of power to heating in the wire. A paltry amount. You're probably losing more in the contacts and controller workings.

For 10AWG it's 20A^2 * 0.00118Ω(6ft) = 2.832W of heat. Not worth spending the money on barely 4W of difference, unless you plan on upgrading to a much more powerful motor (like 40+A).

Now that I think of it, I wonder what I'm losing to heat? 33^2A * 0.00187Ω(8ft) = 16.29144W of heat. Had I went with 14, I would have been losing 25.87464W of heat. Still a small amount compared to the 1300W I'm running. The motor itself is probably losing dozens if not hundreds of watts to inefficiencies.

The author of this post isn't responsible for any injury, disability or dismemberment, death, financial loss, illness, addiction, hereditary disease, or any other undesirable consequence or general misfortune resulting from use of the "information" contai

andrew
andrew's picture
Offline
Last seen: 14 years 1 month ago
Joined: Tuesday, November 28, 2006 - 17:21
Points: 1361
Re: Wire size for 1200W?

What system voltage does the scooter run at?

[url=/forum-topic/motorcycles-and-large-scooters/587-my-kz750-electric-motorcycle-project]KZ750 Motorcycle Conversion[/url]
[url=/forum-topic/motorcycles-and-large-scooters/588-fixing-my-chinese-scooter]900 watt scooter[/url]
Pic from http://www.electri

LinkOfHyrule
LinkOfHyrule's picture
Offline
Last seen: 14 years 9 months ago
Joined: Wednesday, October 17, 2007 - 14:54
Points: 730
Re: Wire size for 1200W?

What system voltage does the scooter run at?

1200W / 20A = 60V. :P

The author of this post isn't responsible for any injury, disability or dismemberment, death, financial loss, illness, addiction, hereditary disease, or any other undesirable consequence or general misfortune resulting from use of the "information" contai

mf70
Offline
Last seen: 6 years 1 month ago
Joined: Friday, December 1, 2006 - 09:01
Points: 712
Re: Wire size for 1200W?

OK, thanks for the feedback. I guess I won't worry about it 'till I wire up the series-parallel plug so I can charge it with a single 12V charger.

It is a 48V system. The current draw may not be exactly 20A max, but it is WAY beyond the 14A I expected from a 700W nominal motor.

Mark

PJD
PJD's picture
Offline
Last seen: 1 day 13 hours ago
Joined: Wednesday, November 22, 2006 - 05:44
Points: 1416
Re: Wire size for 1200W?

It is a 48V system. The current draw may not be exactly 20A max, but it is WAY beyond the 14A I expected from a 700W nominal motor.

Motor wattage ratings are usually conservative, continuous-duty ratings and have nothing to do with the power the motor is capable of safely producing for shorter (but still minutes-long) periods of time.

My "2000 watt" e-max scooter motors have been run, even in hot weather, at 5000 watts, for 2-3 minutes, without problems.

BTW, I use 8AWG wiring. Never noticed any heating at the wires or connectors.

LinkOfHyrule
LinkOfHyrule's picture
Offline
Last seen: 14 years 9 months ago
Joined: Wednesday, October 17, 2007 - 14:54
Points: 730
Re: Wire size for 1200W?

My "2000 watt" e-max scooter motors have been run, even in hot weather, at 5000 watts, for 2-3 minutes, without problems.

My G1 skateboard's 200W motor has been run at 48V and 33A. In other words, over 700% of it's rating. Didn't take it on a very long ride, but it barely got warm 8).

I was using crappy 16AWG wiring, but it didn't get very warm.

The author of this post isn't responsible for any injury, disability or dismemberment, death, financial loss, illness, addiction, hereditary disease, or any other undesirable consequence or general misfortune resulting from use of the "information" contai

Log in or register to post comments


Who's online

There are currently 0 users online.

Who's new

  • xovacharging
  • stuuno
  • marce002
  • Heiwarsot
  • headsupcorporation

Support V is for Voltage