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Registered Member #1025
Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566
Hi guys, Recently I built a motorized bike based on 1000W gear-less brush-less hub motor. I’m really really really enjoying this thing so I thought that some of you might be interested. The motor is a Chinese product and seems pretty robust ( I was inside and there is nothing what can be destroyed except the seams which can be easilly replaced). The battery is made of two batteries. The one inside the frame is 36V 15AH LiFePO4 (that one was included as a part of my first 500W motor which was also great but... I wanted more ;) ) second battery placed on the porter is 12V 20AH LiFePO4 (see below for details) connected in series to get final 48V. The bike can run over 50Km distance with minimum pedaling and the max speed is 45Km per hour and believe me in the terrain it is more than enough ;)
I found the link for the kit (but I bought it from a different distributor via e-bay, but it is the same product)
Just in case somebody is interested I’m glad to share my 4months experience…
The bike beeing recharged
The 1000W hub motor
An extra battery to get 48V. I bought more pieces of these from a company producing electric cars. They were relatively cheap and I'm pretty curious about their performance and manily the longevity, because they lack balancers (according to the guys I bouht it from they should be balanced electrochemically - something I've never heard off ).
I love the night riding - here is is my set of four 3W LED lights
Registered Member #1643
Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039
Looks good, I would make one too but it's illegal here to have any motorized vehicles on sidewalks/street that isn't license. Sadly, including homebrew motorized bikes :(
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
same here.. i am attempting to reuse dead Apple laptop packs that failed due to the electronics board. So far only the swollen one was 100% dead, all the others have good cells.
(yes I am aware of the hazards of Lipos, I hava a diagram for a 3 layer failsafe charger including individual cell balancing using 1381 sensor ICs)
Registered Member #1025
Joined: Sun Sept 23 2007, 07:53PM
Location: Czech Rep.
Posts: 566
So the bike upgrade means minimum extra 15Kg (Still ok for a robust bike to carry even in heavy terrain).
Chris - I don't think your bike is good enough to handle 2KW in electric (it is roughly like 7KW petrol engine!) . You can get injured very easily in case you place so much power on a frame and/or compounds which are not rather expensive and designed for extremes.
Andre - your LiPo's from laptop are most likely not enough. My batteries are 9Kg in total - the latest Lithium technology available - they can provide 50Km so you can calculate a liner distance decrease based on the weight of your cells.
One more important advice for those of you who plan to use front hub motors. It is quite tricky to place the motor into the modern frame forks. Also the pulling power goes right the opposite way than what the forks are designed for. I already destroyed one fork with 1KW motor - the fixtures broke apart... So, it is not a toy anymore - do everything properly and carefully!
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Mates wrote ...
Chris - I don't think your bike is good enough to handle 2KW in electric (it is roughly like 7KW petrol engine!) . You can get injured very easily in case you place so much power on a frame and/or compounds which are not rather expensive and designed for extremes.
Andre - your LiPo's from laptop are most likely not enough. My batteries are 9Kg in total - the latest Lithium technology available - they can provide 50Km so you can calculate a liner distance decrease based on the weight of your cells.
+1 on both. I'd be uncomfortable doing this with some Wal-Mart bike you found at the dump. I was out visiting my local wheelbuilder a while back, and he was building two wheels with 500W hub motors for an offroad electric wheelchair project. He used the heaviest spokes he could get and downhill MTB rims.
I'm not at all sure how suspension forks would cope with the torque from a motor in the front wheel, either. I'd put it in the rear wheel, or get some heavy-ass rigid forks from Surly or whoever.
Also, when sizing battery packs consider that the average bike rider can put out something like 200W of mechanical power for an hour or two, and maybe 500W for short periods. Racing cyclists can do at least twice that, and weekend warriors like me are somewhere in the middle. If you put a 50 watt-hour battery pack from a laptop on a bike, with a maximum output of maybe 60 or 100W, it's going to be about as much use as harnessing a large hamster.
Registered Member #96
Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
um.. more than 50W, these are 65-80Wh packs, and I am using eight of them (!)
main problem is going to be balancing the cells, I have a cunning plan to do this involving very careful monitoring and charging of each individual cell in the pack separately to its rated voltage followed by a constant voltage to 0.1C.
Registered Member #1749
Joined: Fri Oct 10 2008, 02:04AM
Location: Claremont New Hampshire
Posts: 497
Steve McConner wrote ...
Mates wrote ...
Chris - I don't think your bike is good enough to handle 2KW in electric (it is roughly like 7KW petrol engine!) . You can get injured very easily in case you place so much power on a frame and/or compounds which are not rather expensive and designed for extremes.
Andre - your LiPo's from laptop are most likely not enough. My batteries are 9Kg in total - the latest Lithium technology available - they can provide 50Km so you can calculate a liner distance decrease based on the weight of your cells.
+1 on both. I'd be uncomfortable doing this with some Wal-Mart bike you found at the dump. I was out visiting my local wheelbuilder a while back, and he was building two wheels with 500W hub motors for an offroad electric wheelchair project. He used the heaviest spokes he could get and downhill MTB rims.
I'm not at all sure how suspension forks would cope with the torque from a motor in the front wheel, either. I'd put it in the rear wheel, or get some heavy-ass rigid forks from Surly or whoever.
Also, when sizing battery packs consider that the average bike rider can put out something like 200W of mechanical power for an hour or two, and maybe 500W for short periods. Racing cyclists can do at least twice that, and weekend warriors like me are somewhere in the middle. If you put a 50 watt-hour battery pack from a laptop on a bike, with a maximum output of maybe 60 or 100W, it's going to be about as much use as harnessing a large hamster.
You could not of said that at a better time I now know how cheap those forks are I bent them out of shape from doing a stoppie and I bent the frame a little bit at the same time just yesterday. And if I use 2000W worth of power I am glad that there is a throttle. Would it work if you buy 2 1000W motor controllers and use the same throttle?
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An electric bike
). 
And if I use 2000W worth of power I am glad that there is a throttle. Would it work if you buy 2 1000W motor controllers and use the same throttle? 