anth_85
10 mW
I am starting to plan a project that'll I'll be building over the winter ready for next year. I am thinking of building an e-bike suitable for part gravel path part road for commuting on, or at least switch between commuting on and commuting on my good carbon fibre bike. I have a 15mile each way journey. This is my thinking please let me know if your see something obvious that I am missing.
I am thinking of using a cyclocross bike, something like a Specialized Tricross Disc or a Cannondale CAADX 105 (I'd really rather a disk based frame). Then fit a rear hub motor, probably 1000w 48v eBay kit, 700c. I know it's over the limit for the road, but making up some time on the off road sections would be nice. I am planning on powering it with 18650 cells that I already have a large amount of. So I am thinking of building a battery of 13 series, which gives a nominal voltage of 48.1 volts, and a maximum of 54.6 volts, I'll of course check the controller can manage that. If I went for 10 parallel my maths are 1000/48 = 20.8ah which at 2ah each gives 2.08C per cell.
For new cells I'd be comfortable with this, but for used cells I'd be happier at 1C. Which then means 20 parallel.
Therefore 13S20P pack is 260 cells (which I do have, tested at 2000 mha+) at 48V20Ah which sounds pretty huge.
I'd also probably look at changing the chainset from a compact to a standard, and the cassette to a wide ratio. The reason being I will be getting help so wont need the easier gears as much, but having a wide range on the cassette is helpful if the battery ever runs out.
So logistically I can buy a pannier rack and put 2x 13s5p packs in each side. I know the main problems with this is the the extra weight of the hub motor and all the batteries directly above it at the rear of the bike. But as a version 1.0 I am happy with the negative effect on handling, I used to use panniers for commuting and didn't think the extra wait was that bad. I can look at moving them to centre of the frame in V1.1. The weigh of each 18650 is about 48g, so 48 x (13*20) = 12,480g = 12.48KG. Considering I'm 110Kg, that is only at 10% of my weight.
The bits I haven't figured out yet are
1- mounting the throttle to the bars, I could mount it directly under the hoods so I either pull the throttle or pull the brake, but my hand couldn't physically do both, or I could go for pedal assist. I'd rather a proper throttle until I got used to riding it so unsure about this.
2- cabling, pulling 20ah is quite a lot, even if it 10ah from each side. I really don't want to risk a overheating the cabling, so If i split the battery into four 13s5p packs. I can use mains cabling, which will be rated for at least 13amps. How do I join them to one 20amp cable to go to the controller?
3- has this been done before? I see lots of mountain bike conversions, but not many semi-road conversions done, is there a reason?
4- has anyone seen a hard plastic pannier bags that goes down the sides of the rear wheel? This is so I can lower the center of gravity, I don't want fabric bags incase of accidents, and I want to do something to manage airflow through them to prevent the cells overheating.
5- am I missing something or is as simple as that?
I am thinking of using a cyclocross bike, something like a Specialized Tricross Disc or a Cannondale CAADX 105 (I'd really rather a disk based frame). Then fit a rear hub motor, probably 1000w 48v eBay kit, 700c. I know it's over the limit for the road, but making up some time on the off road sections would be nice. I am planning on powering it with 18650 cells that I already have a large amount of. So I am thinking of building a battery of 13 series, which gives a nominal voltage of 48.1 volts, and a maximum of 54.6 volts, I'll of course check the controller can manage that. If I went for 10 parallel my maths are 1000/48 = 20.8ah which at 2ah each gives 2.08C per cell.
For new cells I'd be comfortable with this, but for used cells I'd be happier at 1C. Which then means 20 parallel.
Therefore 13S20P pack is 260 cells (which I do have, tested at 2000 mha+) at 48V20Ah which sounds pretty huge.
I'd also probably look at changing the chainset from a compact to a standard, and the cassette to a wide ratio. The reason being I will be getting help so wont need the easier gears as much, but having a wide range on the cassette is helpful if the battery ever runs out.
So logistically I can buy a pannier rack and put 2x 13s5p packs in each side. I know the main problems with this is the the extra weight of the hub motor and all the batteries directly above it at the rear of the bike. But as a version 1.0 I am happy with the negative effect on handling, I used to use panniers for commuting and didn't think the extra wait was that bad. I can look at moving them to centre of the frame in V1.1. The weigh of each 18650 is about 48g, so 48 x (13*20) = 12,480g = 12.48KG. Considering I'm 110Kg, that is only at 10% of my weight.
The bits I haven't figured out yet are
1- mounting the throttle to the bars, I could mount it directly under the hoods so I either pull the throttle or pull the brake, but my hand couldn't physically do both, or I could go for pedal assist. I'd rather a proper throttle until I got used to riding it so unsure about this.
2- cabling, pulling 20ah is quite a lot, even if it 10ah from each side. I really don't want to risk a overheating the cabling, so If i split the battery into four 13s5p packs. I can use mains cabling, which will be rated for at least 13amps. How do I join them to one 20amp cable to go to the controller?
3- has this been done before? I see lots of mountain bike conversions, but not many semi-road conversions done, is there a reason?
4- has anyone seen a hard plastic pannier bags that goes down the sides of the rear wheel? This is so I can lower the center of gravity, I don't want fabric bags incase of accidents, and I want to do something to manage airflow through them to prevent the cells overheating.
5- am I missing something or is as simple as that?
