Playing with the calculatorhttp://ebikes.ca/simulator/
I find it correctly estimates my current bike. Although it is a stokemonkey, and will perform significantly differently on steep hills because of gearing, at high speeds it looks pretty accurate:
Clyte 406 motor, 20A controller, PING 15AH battery
, full recumbent wind resistance, gives 0% grade speed on the flats of 27 MPH, 15.3 WH/M, 414 watts, and 37 mi range. That's pretty close to what I can do now. With the Cycle Analyst I can dial down the power a little and get 40-50 mile range at 20MPH, which matches up with the calculator if I dial the throttle back to maybe 90%.
So how to model the new bike? A basic rule is that 2X the speed takes 4X the power. The simulator also tells us that hill climbing is *linear* with speed - air friction isn't the main drag, it is oomphing up the hill. That I didn't know. Try modeling a steep hill if you don't believe it.
So I am looking at 4X the battery to go twice as fast the same distance. About 60 Amp Hours. Ping says that is 50 Lbs of batteries. Wow! My current battery is 12 lbs.
So hauling my tub-O-lard butt and my relatively heavy trike and battery up a hill will be a 120 kilogram affair. Say 150 KG so I can haul a few groceries.
I have a lot of 6% grades and a few very steep grades. 15%-20%. They are short, however. Let's say I stay with the Full Recumbent air resistance, although my air resistance is likely to be lower with a faring.
With a 150KG bike, full recumbent, Clyte 5303 motor, 52C 0.2 ohm 30 AH battery (48V nominal) this vehicle should go 39 MPH on the flats and have a 46 mile range. Hmm. How to model dual motors and hilly terrain?
I am going to say that the black "load line" doesn't change, however the motor power will be 50% of the load since there are two motors. THe load line crosses 40MPH at 1000 watts. This is simulated well with a drag CdA of 0.25 and a Cr of .0005. If I change the CdA to .012, that seems to simulate the load on one motor of 2 pretty well, making the load line go to about half or a little over 500 watts.
With a 72V 0.2 ohm 30 AH battery (half the expected battery pack), a 25A controller, 62% throttle, 0% grade I am at about 40 MPH and 550 watts on one motor. Range estimate is nuts at 121 miles.
I will cut the wieght to half for estimating grades since there are two motors. On a nice easy 6% grade as encountered on 4 lanes, I am at a respectable 34 MPH with no overheating. On a 15% grade, I am at 20 MPH and overheat in 25 minutes, which is fine since the steep places are short, maybe 1/4 mile. THis is looking like a really respectable machine, sumpin' that'll get me to the store and back.
How to estimate range? Modeling my old bike at a 1% grade gives a pretty good estimate of the range I am getting. Some hills are short and steep, sometimes I am on the flat or downhill. So if I estimate the above parameters at a 1% grade, throttling back to 40 MPH, I get 51 miles range with a 15 AH battery per motor. Hmm - this is hard to swallow, since I had earlier estimated a 60 AH (30 AH per motor) battery which is twice that size.
I could certainly set it up with two 72V 15 AH batteries with provisions for two more, then ride the darn thing and find out for sure what the range is in my terrain. Might be a plan!
Efficiency - comparing a single motor (150KGs, .25 CdA, 40 MPH) with two motors (half the wieght and CdA) I find that I am at 75% efficiency on the flats, 75% on a 12% grade and 65% on a 15% grade with the dual motor setup limited to 40 MPH with the throttle. THe single motor is 81% on the flats, 31% on a 12% grade won't go up a 15% grade at all. Here is where the dual motor shines, hauling my lard butt and a big battery up a hill with high efficiency.