# Whatsup with Watts?

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jdh2550_1
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Whatsup with Watts?

Hi,

My high school physics tells me that Power (Watts) = Current (amp) * Potential (volts).

So, my XM-2000 states that it has a 40 amp controller and 60 volt battery pack. That means peak power would be 2400 Watts. Now, given that the speed and distance specs are "optimistic" I find it strange that the power rating would be pessimistic.

So, can anyone explain how the XM-2000 gets its 2000 Watt rating? Is it to do with motor efficiency? Or complete system efficiency? (i.e. losses in the battery, controller, wire and motor) This would make the system about 83% efficient - 2400 * 0.83 = 1992. That sounds plausible.

Any thoughts?

Thanks,
John H.
XM-2000
Ann Arbor, MI, USA.

andrew
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Re: Whatsup with Watts?

So, can anyone explain how the XM-2000 gets its 2000 Watt rating?

The 2000 watt spec is the continuous output power rating of the motor. This is how much power the motor can put out at 60v without overheating. It has nothing to do with how much power the scooter will actually produce.

So, my XM-2000 states that it has a 40 amp controller and 60 volt battery pack. That means peak power would be 2400 Watts.

After you figure in motor losses, than the theoretical peak power is probably about 2000 watts, but I can't say for sure without more information.

---
Avatar taken from http://www.electricmotorbike.org/
Anyone got one they want to sell?
My KZ750 Project: here

[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

PJD
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Re: Whatsup with Watts?

Nothing too odd about it. The motor's rating is 2000 (electrical) watts for continuous duty. It can draw and produce much more power than this for shorter periods, and hundreds of percent more for very brief periods.

Yes, I know, it seems it would be like a car manufacturer under-representing the horsepower of the engine. But you have to understand that the sellers of these scooters usually don't know an amp from a volt.

Also, the motors are often conservatively rated. My e-max was also rated at 2000 watts but with my modifications it often sees up to 5 minutes continuous usage at about 3200 watts, without getting too hot. Admittedly, the moderate summer temperatures around here help.

mark IV
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Joined: Wednesday, July 18, 2007 - 12:36
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Re: Whatsup with Watts?

Wow that's a lot of power, must have good pull.
I remember my elec class formula was E/RxI but don't know if this applies tho motors.
However, a 500 watt 48V Hyosung(Korean) scooter I test drove last week had ample power with the speed limited to 35 KM/H, priced at \$1,400 cdn.

E-bike platforms so far:
36 v geared Hienzmann frnt wheel dr (6yrs old)
36 V 350-watt Bionx-li-on hybrid bike (new)

E-bike platforms so far:
36 v geared Hienzmann frnt wheel dr (6yrs old)
36 V 350-watt Bionx-li-on hybrid bike (new)

PJD
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Last seen: 1 week 21 hours ago
Joined: Wednesday, November 22, 2006 - 05:44
Points: 1416
Re: Whatsup with Watts?

Yes, it was a needed improvement. Goes 35-40 mph (about 60 kph) up an 8% hill. And, even battery range was unaffected - the higher amperage keeps the hub motor in the peak of it's power output curve while getting you up the hill faster - you actually use no more, and possibly less electrical energy in up and down hill situations. Why the manufacturer didn't know this and set the controller amperage limits accordingly shows how little design effort they put into these scooters.

andrew
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Last seen: 13 years 3 days ago
Joined: Tuesday, November 28, 2006 - 17:21
Points: 1361
Re: Whatsup with Watts?

I'd be really interested to see how the MX-2000 motor would do with more current. How hot is the motor casing getting after a long run?

---
Avatar taken from http://www.electricmotorbike.org/
Anyone got one they want to sell?
My KZ750 Project: here

[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

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