mcstar
100 W
A few weeks ago I bought a BL-36 from Wilderness Energy. This is my first e-bike. The new version of the BL-36 is rated at 650Watts, and has a start from 0 controller. Since it was rated at the same power as the brushed model and is supposed to get more range than the brushed motor, I decided the extra $50 or so was worth it. I have not been disappointed. My only complaint has been that the rim they sent me was bent enough to cause the front brakes to tug when braking at high speed. I'm using this bike as a commuter to work.
My cycling computer is a garmin Edge 305 with gps which is able to log altitude, grade, speed, cadence, heart rate etc. My commute is almost exactly 13miles and consists of an insane 200ft climb at the last 1/2mile or so. The altitude at my home is within 20feet of the altitude at work, so most of the trip is at a slight down grade with plenty of hills in between. At 36volts I'm able to make the trip in about 45minutes at an average speed of 16.1mph. Most of the trip is spent at about 20mph. This weekend I upgraded to 48Volts by mounting another 12v 12AH sla battery in the frame under the seat. I wired it in series with the existing 36v pack and in parallel for charging independantly with a 12v charger. The 36V pack is wired in series as before so it can be charged with it's standard 36v charger. Preliminary testing revealed a substantial increase in torque and top speed and I was delighted to have the extra speed. I took it on a 8mile out and back this weekend and took advantage of opportunity charging for 3 hours at my destination. I had plenty of speed both directions and felt confident I could get to work on the now 48v pack just fine.
However, it turns out that was not so !! This morning I left with a full charge and cruised at about 24-26 mph for the majority of the commute. It's a fine speed, but then at about mile 11 I noticed I could no longer hold anything above 21mph, soon I was at 18mph and I felt that I should save any remaining juice to assit on the upcoming 200ft ascent. The climb was difficult I made in the lowest gear with only a gentle assist by the motor. I figure it was about carrying it's own weight. I petted the throttle gently to avoid overly discharging the batteries. Huff, huff, huff I finally made it and cruised into work at about 12mph. The system had lost almost all capacity by then.
When I got to work I decided to do some research to determine why I'd run so short on power. This is what I found. Using the speed/power calculator http://www.kreuzotter.de/english/espeed.htm, I determined that at an average speed of 24mph with the load I'm carrying (198lb rider + 100 bike + gear + 3mph wind) I'm using something like 544watts of power to maintain the speed. At 48v this is a current of more than 11amps. According to the datasheet at http://www.powerstream.com/BB.htm these batteries can only hold that discharge rate for about 35minutes. According to the garmin training center, at about 30 minutes my speed started to fall below 21 mph, so it appears that the batteries had done all they could by then.
What to do, how shall I get home without running out of power? Well the batteries are charging here at work, and using the bicycle speed/power calculator again, I found that at 20mph my power consumption is only 347watts. That's a 200watt drop for only 3mph! At 48v this gives me an average current of 7.2 amps. According to the sla datasheet at 7.2amps the batteries should be good for at least an hour. This is more than enough to travel the 13miles home. So, if I set my garmin to sound an alert when my speed hits 21mph and ride just below the alarm, I should be fine.
This is what I love about e-biking, I couldn't care 2cents about C02 emissions, but on a motor cycle, you just turn the throttle and go. Very little thought is involved because the engine is able to easily carry you with hp to spare. But with electric, you're constantly thinking. "How can get the range I need? How can I improve performance or maximize efficency. It's keeps your mind engagad and I love that!
My cycling computer is a garmin Edge 305 with gps which is able to log altitude, grade, speed, cadence, heart rate etc. My commute is almost exactly 13miles and consists of an insane 200ft climb at the last 1/2mile or so. The altitude at my home is within 20feet of the altitude at work, so most of the trip is at a slight down grade with plenty of hills in between. At 36volts I'm able to make the trip in about 45minutes at an average speed of 16.1mph. Most of the trip is spent at about 20mph. This weekend I upgraded to 48Volts by mounting another 12v 12AH sla battery in the frame under the seat. I wired it in series with the existing 36v pack and in parallel for charging independantly with a 12v charger. The 36V pack is wired in series as before so it can be charged with it's standard 36v charger. Preliminary testing revealed a substantial increase in torque and top speed and I was delighted to have the extra speed. I took it on a 8mile out and back this weekend and took advantage of opportunity charging for 3 hours at my destination. I had plenty of speed both directions and felt confident I could get to work on the now 48v pack just fine.
However, it turns out that was not so !! This morning I left with a full charge and cruised at about 24-26 mph for the majority of the commute. It's a fine speed, but then at about mile 11 I noticed I could no longer hold anything above 21mph, soon I was at 18mph and I felt that I should save any remaining juice to assit on the upcoming 200ft ascent. The climb was difficult I made in the lowest gear with only a gentle assist by the motor. I figure it was about carrying it's own weight. I petted the throttle gently to avoid overly discharging the batteries. Huff, huff, huff I finally made it and cruised into work at about 12mph. The system had lost almost all capacity by then.
When I got to work I decided to do some research to determine why I'd run so short on power. This is what I found. Using the speed/power calculator http://www.kreuzotter.de/english/espeed.htm, I determined that at an average speed of 24mph with the load I'm carrying (198lb rider + 100 bike + gear + 3mph wind) I'm using something like 544watts of power to maintain the speed. At 48v this is a current of more than 11amps. According to the datasheet at http://www.powerstream.com/BB.htm these batteries can only hold that discharge rate for about 35minutes. According to the garmin training center, at about 30 minutes my speed started to fall below 21 mph, so it appears that the batteries had done all they could by then.
What to do, how shall I get home without running out of power? Well the batteries are charging here at work, and using the bicycle speed/power calculator again, I found that at 20mph my power consumption is only 347watts. That's a 200watt drop for only 3mph! At 48v this gives me an average current of 7.2 amps. According to the sla datasheet at 7.2amps the batteries should be good for at least an hour. This is more than enough to travel the 13miles home. So, if I set my garmin to sound an alert when my speed hits 21mph and ride just below the alarm, I should be fine.
This is what I love about e-biking, I couldn't care 2cents about C02 emissions, but on a motor cycle, you just turn the throttle and go. Very little thought is involved because the engine is able to easily carry you with hp to spare. But with electric, you're constantly thinking. "How can get the range I need? How can I improve performance or maximize efficency. It's keeps your mind engagad and I love that!