jn1 said...
pweedas: Not sure where you got 19 HP from ?.. The web site is quoting 54 ponies (I assume from the back wheel ?). Yes, I agree with you about the L-ion batteries. Their capacity decays as soon as they are manufactured, unless Zero have a special manufacturing technique that prevents this ?
No. I think they have a special advertising campaign that prevents this.
So where did the 19hp come from?
I ran through a few figures at variious power settings to see how realistic the stats quoted in the videos were, considering the capacity of the battery,.. I didn't say it all because most will glaze over and not bother with it,. but since you ask,..
Here are a few details.
Firstly, the figures I take as accurate are the battery capacity because it's easy to read off the label on teh battery and quote it, and although it's also usually overrated, sometimes it's accurate, so lets say it is.
They say it's 14.2 KWhrs.
Secondly, the quoted maximum engine power of 67hp equates to 50 kilowatts and would be the power consumed by the motor, not the power output of the motor. They usually rate electric motors that way rather than state the power output. Thus when they say a 50kw motor you can take it they mean it draws 50kw, not that it will supply 50kw.
It would only output 50kw if it was 100% efficient. I discounted that error and thus continued on the basis of a 100% efficiency.
so,..Take the case of a flat out run at the stated 102 mph.
Flat out the motor draws 50kw out of a 14.2kWhr battery.
Thus it would last 14.2/50 hours = 0.28 hrs @102mph gives a distance of 30 miles (= 47km total) .
With a good lithium battery you can discharge it in 15 minutes but it will get quite hot and it degrades the battery if you do it often. I think the instructions would advise against it.
Thus a range of 30 miles is the worst case conditon.
However, you can realisticaly drain the whole battery in 1 hour without damage to the cells so I used a 1 hour discharge rate.
14.2 Kwhr used over 1 hour is obviously a 14 kw motor power draw, which equates to 14.2 / 0.746 = 19 hp.
I was then very generous and said that under ideal conditions, since they claim a top speed of 102mph, lets say they achieve that with just the 19hp (14kw) power. Since that was for 1 whole hour then that makes total distance of 102 miles, which is still a long way short of the claimed 171 miles even using the most wildly optimistic figures.
So,.. let's be a bit more realistic.
I think 14 kw under no wind and flat road and small rider lying flat on tank, would give a speed of about 65 miles per hour. Thus the range of the bike at 65 miles per hour would be a lot closer to 65 miles than it would be to 171 miles.
If someone says you could get 75mph out of a 19 hp motor, that still only gives a range of 75 miles.
Next off,..what conditions might result in a range of 171 miles?
We can try an educated guess here,..
With a power draw of say 3.25kw you could expect a speed of around 40 mph, and the battery at that rate would last around 4.4 hours.
4.4 hours at 40 mph would give a range of 176 miles.
These are ball park figures and they still assume a 100% efficient motor.
They also assume no start/stop driving, and very easy throttle application,.. which no-one actually does in practice.
But yes,.. around town at 30 to 40 mph and very easy on the throttle, and a new battery, you could probably get the 171 miles stated. But who's going to do that?
