View Single Post
Old 02-08-09, 03:26 PM
  #16  
safe
Senior Member
 
safe's Avatar
 
Join Date: Feb 2009
Posts: 160
Mentioned: 1 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 1 Time in 1 Post
Using the online calculator: (go ahead and plug in values to prove to yourself it's true)

http://www.me.psu.edu/lamancusa/Prod...e/bikecalc.htm

Start with all the default values...



Downhill (5% negative slope for 10 miles)

Freewheel - 10 miles / 24.35 mph = 0.41 hours (net power gain/loss is zero)

Regen - 10 miles / 15.00 mph = 0.67 hours (behind by 0.26 hours)

Recaptured Energy = 0.133 hp * 746 watt = 99.22 watt

99.22 watt * 0.67 hours = 66.48 Wh * 0.7 (motor losses) = 46.5 Wh

46.5 Wh * 0.9 (battery losses) = 42 Wh (this is the energy recovered)



Uphill (5% positive slope for 10 miles)

Freewheel - 10 miles / 7 mph = 1.43 hours

Power Needed - 0.187 hp * 746 watt = 139.5 watt / 0.7 (motor losses) = 199.3 watt

199.3 watt * 1.43 hours = 285 Wh

Regen - Must do 10 miles in 1.43 hours - 0.26 hours = 1.17 hours

10 miles / 11.7 mph = 1.17 hours

Power Needed - 0.337 hp * 746 watt = 251.4 watt / 0.7 (motor losses) = 359.1 watt

359.1 watt * 1.17 hours = 420 Wh

...but we get to subtract the "savings" so the actual value is:

420 Wh - 42 Wh = 378 Wh



---------------------------------



Conclusion:

For the regen ebike to reach the second peak at the same time as the freewheel ebike it will use:

378 Wh - 285 Wh = 93 Wh more than the freewheel...


---------------------------------

Have I made any mistakes? (it's possible, mistakes are always possible)

.

Last edited by safe; 02-08-09 at 03:33 PM.
safe is offline