W/O trailer trailer w full load
Ride length: 24.59 km 24.48 km
Time: 52 min 29 sec 51min 19 sec
Av. speed: 28.1 km/h 28.60 km/h
Power usage:
6.85 Ah 9.81 Ah
386.06 Wh 501.27 Wh
15.70 Wh/km 20.60Wh/km
Max speed: 45.0 km/h 35.50 km/h
Start voltage 58.10 58.10
Start voltage 58.10 58.10
Finish voltage 53.00 50.90
trailer no load full trailer w/o batteries
Tonight's test was to find the energy cost of the trailer with all battery boxes in order to estimate the energy loss from the additional aerodynamic resistance. The trailer was without any batteries. So we had the full aerodynamic losses with very little additional inertial losses. This will allow us to subtract the rolling resistance (1 Wh/km) plus aerodynamic resistance from the total load of the full trailer (4.9 Wh/km). Logically, this result can only be for the inertial resistance of the remaining load.
Tonight, with the added aerodynamic resistance, there was an added 1.5 Wh/km of energy consumption. Therefore, 4.9 Wh/km total trailer resistance minus 1.0 Wh/km rolling resistance leaves 3.9 Wh/km. Subtracting 1.5 Wh/km of aero losses leaves 2.4 Wh/km as the energy cost of transporting the remaining 90 lbs of cargo or .027 Wh/km per lb.
The total weight of the bike, rider, trailer, and cargo is 76 lbs, 255 lbs, 19 lbs, and 113 lbs (90 lb battery + 23 lb battery boxes), respectively for a total 463 lbs. Total rolling resistance energy needed to move this weight at 28 km/h is (463 lbs x .027 Wh/km/lb) 12.5 Wh/km.
Rolling resistance of trailer is 1.0 Wh/km but this is with 19 lbs of added weight. The 19 lbs of added weight use up (19 x .027) .5 Wh/km leaving .5 Wh/km for rolling resistance.
Since this figure is for two wheels on the trailer there is no reason not to conclude that the bike's two wheels have the same resistance. So the total rolling resistance for a loaded bike and trailer going 28 km/h is 1.0 Wh/km.
Total energy for the loaded bike and trailer at 28 km/h is 20.6 Wh/km. Therefore, subtracting 12.5 Wh/km (inertial or weight resistance) and 1 Wh/km (rolling resistance) leaves us with 7.1 Wh/km of energy use to overcome aerodynamic drag.
Total energy use = 20.6 Wh/km = 100.0%
Aero resistance = 7.1 Wh/km = 35.0%
Rolling resistance = 1.0 Wh/km = 5.0%
Inertial resistance = 12.5 Wh/km = 60.0%
Just remember: these figures are for a speed of 28 km/h. Someday I will do a series of tests at 35 km/h to show how fast aero drag increases as a proportion of overall drag.
Fun fact: If I lost 60 lb I could save (60 x .027 =) 1.62 Wh/km.
On a 350 km trip this amounts to 567 Wh. That's 75% of another battery. Something to think about.
Update: The Grin computer shows that losing 60 lbs would only save .80 Wh/km or about 280 Wh over a 350 km trip. I think the computer is underestimating the number.
Right now, my brain is tired so I'll get back to this another time.
trailer no load full trailer w/o batteries
Ride length: 24.60 km 24.61km
Time: 51 min 28 sec 52 min 1 sec
Av. speed: 28.6 km/h 28.30 km/h
Power usage:
7.92 Ah 8.73 Ah
414.39 Wh 447.00 Wh
16.70 Wh/km 18.20 Wh/km
Max speed: 42.90 km/h 36.70 km/h
Start voltage 58.10 58.10
Finish voltage 52.00 50.90
Tonight's test was to find the energy cost of the trailer with all battery boxes in order to estimate the energy loss from the additional aerodynamic resistance. The trailer was without any batteries. So we had the full aerodynamic losses with very little additional inertial losses. This will allow us to subtract the rolling resistance (1 Wh/km) plus aerodynamic resistance from the total load of the full trailer (4.9 Wh/km). Logically, this result can only be for the inertial resistance of the remaining load.
Tonight, with the added aerodynamic resistance, there was an added 1.5 Wh/km of energy consumption. Therefore, 4.9 Wh/km total trailer resistance minus 1.0 Wh/km rolling resistance leaves 3.9 Wh/km. Subtracting 1.5 Wh/km of aero losses leaves 2.4 Wh/km as the energy cost of transporting the remaining 90 lbs of cargo or .027 Wh/km per lb.
The total weight of the bike, rider, trailer, and cargo is 76 lbs, 255 lbs, 19 lbs, and 113 lbs (90 lb battery + 23 lb battery boxes), respectively for a total 463 lbs. Total rolling resistance energy needed to move this weight at 28 km/h is (463 lbs x .027 Wh/km/lb) 12.5 Wh/km.
Rolling resistance of trailer is 1.0 Wh/km but this is with 19 lbs of added weight. The 19 lbs of added weight use up (19 x .027) .5 Wh/km leaving .5 Wh/km for rolling resistance.
Since this figure is for two wheels on the trailer there is no reason not to conclude that the bike's two wheels have the same resistance. So the total rolling resistance for a loaded bike and trailer going 28 km/h is 1.0 Wh/km.
Total energy for the loaded bike and trailer at 28 km/h is 20.6 Wh/km. Therefore, subtracting 12.5 Wh/km (inertial or weight resistance) and 1 Wh/km (rolling resistance) leaves us with 7.1 Wh/km of energy use to overcome aerodynamic drag.
Total energy use = 20.6 Wh/km = 100.0%
Aero resistance = 7.1 Wh/km = 35.0%
Rolling resistance = 1.0 Wh/km = 5.0%
Inertial resistance = 12.5 Wh/km = 60.0%
Just remember: these figures are for a speed of 28 km/h. Someday I will do a series of tests at 35 km/h to show how fast aero drag increases as a proportion of overall drag.
Fun fact: If I lost 60 lb I could save (60 x .027 =) 1.62 Wh/km.
On a 350 km trip this amounts to 567 Wh. That's 75% of another battery. Something to think about.
Update: The Grin computer shows that losing 60 lbs would only save .80 Wh/km or about 280 Wh over a 350 km trip. I think the computer is underestimating the number.
Right now, my brain is tired so I'll get back to this another time.
