Hi all. I've gained a lot of useful information from this forum, so now that I'm actually starting my build, I thought I'd document my build to possibly help others in the future.
My motivation to build an ebike is that I'm moving to France next year (or so) and would like to explore the countryside. There is a good train network, but it doesn't go everywhere. For example, if you want to see the WW2 sites at Normandy, the train can take you to the general area, but there are lots of little museums and monuments that are really too far apart to walk. I'd rather avoid the expense of a car. Many people use small gas-powered scooters or motorbikes, but I would really rather have an electric vehicle, and I've discovered that there is an extensive network of bike trails around Europe that I could access if I keep my bike within EU rules. I'm imagining pedaling though fields of lavender or grapes with a pannier bag full of bread, cheese, and wine.
I don't have a big budget, as I've been saving my pennies for this adventure. I'm shooting for <$600, including the bike.
A folding bike can be taken on any train in France as ordinary luggage without special arrangement. I'm small and not very strong, so I want to keep it lightweight. That led me to the Vilano Urbana folding bike, which is 22 lbs with 20" wheels. I can save a few pounds by changing out the heavy (steel) seatpost and seat for an aluminum one. It has coaster brakes and is fixed speed, which I like, because I haven't ridden a bike since I was a kid, and so kid bikes are my comfort zone. So there's my donor bike.
It cost $200 shipped from Florida.
I will need a rear rack for the battery and that bread/cheese/wine, and couldn't find a lightweight cheap one that would fit my 20" wheels, so I bought some aluminum U-channel at Home Depot ($8) and made one:
In order to avoid losing the rear coaster brake, I went with a front hub motor. I've read this is not a good idea for all ebikes because forks are not designed to take high torque, but because EU regulations limit the motor to 250W and the speed to 25kph, and the fork of my bike is steel, it should be okay.
I ordered a cheap Chinese motor from ebay ($109 shipped) https://www.ebay.com/itm/36V-250W-3...var=462985163234&_trksid=p2057872.m2749.l2649. It appears to be the same as the MXUS XF07, although it was not sold as such. To satisfy the EU regulations, it is 250W, although I've read that they are often capable of higher power, and labeled 250W to satisfy the EU. I went with a geared motor, because it is lighter and better for pedaling if your battery is dead. The freewheel spins nicely, although it has drag in the opposite direction.
The motor created two problems for me. One is that even though the motor is supposed to fit a 100mm dropout, and the bike front dropout is supposed to be 100mm, the motor has various bumps that require it to actually have a wider fork. And the bike's fork is actually 95mm. So upon consulting the internet about spreading a steel fork, I went for it. I wrapped a dish towel around several pieces of wood and tapped them into the fork to spread it out. And it worked, just barely. Here is the motor in the fork. You can see how close it is to each side of the fork, which is spread to about 110mm
The other problem is that the hub motor has 36 holes and my rims have 28. So I did some internet research and found this: https://www.sheldonbrown.com/mismatch/index.htm. I did all the math three times (protip: Excel's trigonometric functions assume that your angles are in radians. Go figure) and came up with spoke lengths. Then I realized how expensive custom-length spokes are. There is an ebay seller who would made Sapim Strongs that are thicker at the hub end, because the holes are larger) for $2 each plus shipping. Finally I found references on regular bike forums to Dan's Comp as a cheap source of spokes. They sold me the custom-length single-butted stainless spokes for 50 cents each. They only had silver, so I ordered non-butted silver spokes for the rear wheel at 25 cents each and still came out ahead. And once I started to take off the old spokes, I realized that the supplied spokes were a bit short, so that the threads were showing, so it's good that I replaced them. Dan's Comp only does business through email, and they are a bit slow to respond, but sent me exactly what I needed, all neatly labeled in envelopes. And once I finally got the order put in, the spokes arrived in a few days.
That lead me to the fun of my first bike wheel lacing. I did the rear wheel first, since I could follow the pattern of the old spokes. Then I did the hub motor. Apparently my math was fine, because it all fit beautifully. I had to modify the instructions because the screws on the motor didn't permit outbound lacing for some holes. I don't have a truing stand, so I just used the bike upside down, and they don't appear to wobble or bounce when I spin them.
I ordered a Brainpower controller and S866 display combo from Aliexpress ($31)https://www.aliexpress.com/item/33004354051.html?spm=a2g0s.9042311.0.0.27424c4dLPUZdW that will allow me to set voltage, max current, and max speed. EU regulations require PAS rather than throttle, but the controller will allow me to install a thumb throttle and turn it off when I'm in Europe and back on in the US. I haven't had a chance to test it yet, as I'm still working on the battery.
Speaking of the battery... you can't take a regular ebike battery on a plane. Too much risk of nasty battery fire. TSA says that you can have as many batteries as you want, as long as each is less than 100 WH. But the international air association limits you to 20 batteries under 100 WH each, so many airlines place the limit there. So I found this thread: https://endless-sphere.com/forums/viewtopic.php?t=72138&start=40 in which cells are snapped into spring holders that are beefed up with copper bus bars. I am making a 20Ah battery (10s 6p), so I'm making the 6p packs out of these spring holders and will shrink-wrap each one, which will be 3.6V x 3.4ah x 6 = 73Wh. Banana plugs connect the 10 packs together once the bike and I are safely in France. I'm going to build an aluminum box that they all will slide into, and that attaches to the side of my rear rack.
I ordered 60 18650 cells from Liitokala (https://www.aliexpress.com/item/32807032859.html?spm=a2g0s.9042311.0.0.27424c4dM8E8KA) for $140. I also ordered a Lii-500 tester ($20), which puts 4 cells at a time through a cycle of charging, then discharging at 250 mA to test actual discharge mAh, then charging again. They are almost done (it takes a full day for 4 cells) and they are averaging the advertised 3400mAh, although a few are down around 3200mAh. I am planning on arranging them so that each pack has approximately the same Ah, so that weaker cells in a pack are charged by their stronger parallel neighbors. If you do it the other way, with the 6 parallel cells matched, the discharge will stop before the stronger packs are empty. That means the weak packs would wear out faster than the strong ones, and make the imbalance worse.
Because the clip in battery packs don't come in a 6-cell variety, I epoxied a 4-cell and 2-cell together. Then I slightly flattened a 12g copper wire to keep it from rolling, and soldered it on to create the parallel bars on each side. Then I added 14g wire (my BMS is 15A max, so my system shouldn't go over that) and the sensor wires. I then added gold-plated copper banana plugs. The plugs have holes in the side so that I could wrap the wires around securely and fill in the little cup with solder. Then I wrapped the exposed wires in stretchy electrical tape.
I was a bit concerned that the snap-in connections would be a point of high resistance and therefore high temperature. So I rigged up a single cell with a phone charger circuit board to see with my FLIR camera if there was a lot of heat at those snap-in points. This is ~0.7A draw off a single cell to a phone, which is 0.2C. That's not much, although if my motor actually operates at 250W, it will draw 0.35C, which is not too far off. Happily, I'm not seeing any hot spots anywhere, and the battery is only a few degrees warmer than the surroundings, even after giving it a few minutes to reach thermal equilibrium. The last picture is a pre-made battery charging pack, and the circuit board and USB plug are clearly getting a lot hotter. I am looking forward to testing the whole pack with the motor, but the throttle still hasn't arrived, and I'm still working on testing the batteries.
That's all I have for now. I will update as I can.
My motivation to build an ebike is that I'm moving to France next year (or so) and would like to explore the countryside. There is a good train network, but it doesn't go everywhere. For example, if you want to see the WW2 sites at Normandy, the train can take you to the general area, but there are lots of little museums and monuments that are really too far apart to walk. I'd rather avoid the expense of a car. Many people use small gas-powered scooters or motorbikes, but I would really rather have an electric vehicle, and I've discovered that there is an extensive network of bike trails around Europe that I could access if I keep my bike within EU rules. I'm imagining pedaling though fields of lavender or grapes with a pannier bag full of bread, cheese, and wine.
I don't have a big budget, as I've been saving my pennies for this adventure. I'm shooting for <$600, including the bike.
A folding bike can be taken on any train in France as ordinary luggage without special arrangement. I'm small and not very strong, so I want to keep it lightweight. That led me to the Vilano Urbana folding bike, which is 22 lbs with 20" wheels. I can save a few pounds by changing out the heavy (steel) seatpost and seat for an aluminum one. It has coaster brakes and is fixed speed, which I like, because I haven't ridden a bike since I was a kid, and so kid bikes are my comfort zone. So there's my donor bike.
It cost $200 shipped from Florida.
I will need a rear rack for the battery and that bread/cheese/wine, and couldn't find a lightweight cheap one that would fit my 20" wheels, so I bought some aluminum U-channel at Home Depot ($8) and made one:
In order to avoid losing the rear coaster brake, I went with a front hub motor. I've read this is not a good idea for all ebikes because forks are not designed to take high torque, but because EU regulations limit the motor to 250W and the speed to 25kph, and the fork of my bike is steel, it should be okay.
I ordered a cheap Chinese motor from ebay ($109 shipped) https://www.ebay.com/itm/36V-250W-3...var=462985163234&_trksid=p2057872.m2749.l2649. It appears to be the same as the MXUS XF07, although it was not sold as such. To satisfy the EU regulations, it is 250W, although I've read that they are often capable of higher power, and labeled 250W to satisfy the EU. I went with a geared motor, because it is lighter and better for pedaling if your battery is dead. The freewheel spins nicely, although it has drag in the opposite direction.
The motor created two problems for me. One is that even though the motor is supposed to fit a 100mm dropout, and the bike front dropout is supposed to be 100mm, the motor has various bumps that require it to actually have a wider fork. And the bike's fork is actually 95mm. So upon consulting the internet about spreading a steel fork, I went for it. I wrapped a dish towel around several pieces of wood and tapped them into the fork to spread it out. And it worked, just barely. Here is the motor in the fork. You can see how close it is to each side of the fork, which is spread to about 110mm
The other problem is that the hub motor has 36 holes and my rims have 28. So I did some internet research and found this: https://www.sheldonbrown.com/mismatch/index.htm. I did all the math three times (protip: Excel's trigonometric functions assume that your angles are in radians. Go figure) and came up with spoke lengths. Then I realized how expensive custom-length spokes are. There is an ebay seller who would made Sapim Strongs that are thicker at the hub end, because the holes are larger) for $2 each plus shipping. Finally I found references on regular bike forums to Dan's Comp as a cheap source of spokes. They sold me the custom-length single-butted stainless spokes for 50 cents each. They only had silver, so I ordered non-butted silver spokes for the rear wheel at 25 cents each and still came out ahead. And once I started to take off the old spokes, I realized that the supplied spokes were a bit short, so that the threads were showing, so it's good that I replaced them. Dan's Comp only does business through email, and they are a bit slow to respond, but sent me exactly what I needed, all neatly labeled in envelopes. And once I finally got the order put in, the spokes arrived in a few days.
That lead me to the fun of my first bike wheel lacing. I did the rear wheel first, since I could follow the pattern of the old spokes. Then I did the hub motor. Apparently my math was fine, because it all fit beautifully. I had to modify the instructions because the screws on the motor didn't permit outbound lacing for some holes. I don't have a truing stand, so I just used the bike upside down, and they don't appear to wobble or bounce when I spin them.
I ordered a Brainpower controller and S866 display combo from Aliexpress ($31)https://www.aliexpress.com/item/33004354051.html?spm=a2g0s.9042311.0.0.27424c4dLPUZdW that will allow me to set voltage, max current, and max speed. EU regulations require PAS rather than throttle, but the controller will allow me to install a thumb throttle and turn it off when I'm in Europe and back on in the US. I haven't had a chance to test it yet, as I'm still working on the battery.
Speaking of the battery... you can't take a regular ebike battery on a plane. Too much risk of nasty battery fire. TSA says that you can have as many batteries as you want, as long as each is less than 100 WH. But the international air association limits you to 20 batteries under 100 WH each, so many airlines place the limit there. So I found this thread: https://endless-sphere.com/forums/viewtopic.php?t=72138&start=40 in which cells are snapped into spring holders that are beefed up with copper bus bars. I am making a 20Ah battery (10s 6p), so I'm making the 6p packs out of these spring holders and will shrink-wrap each one, which will be 3.6V x 3.4ah x 6 = 73Wh. Banana plugs connect the 10 packs together once the bike and I are safely in France. I'm going to build an aluminum box that they all will slide into, and that attaches to the side of my rear rack.
I ordered 60 18650 cells from Liitokala (https://www.aliexpress.com/item/32807032859.html?spm=a2g0s.9042311.0.0.27424c4dM8E8KA) for $140. I also ordered a Lii-500 tester ($20), which puts 4 cells at a time through a cycle of charging, then discharging at 250 mA to test actual discharge mAh, then charging again. They are almost done (it takes a full day for 4 cells) and they are averaging the advertised 3400mAh, although a few are down around 3200mAh. I am planning on arranging them so that each pack has approximately the same Ah, so that weaker cells in a pack are charged by their stronger parallel neighbors. If you do it the other way, with the 6 parallel cells matched, the discharge will stop before the stronger packs are empty. That means the weak packs would wear out faster than the strong ones, and make the imbalance worse.
Because the clip in battery packs don't come in a 6-cell variety, I epoxied a 4-cell and 2-cell together. Then I slightly flattened a 12g copper wire to keep it from rolling, and soldered it on to create the parallel bars on each side. Then I added 14g wire (my BMS is 15A max, so my system shouldn't go over that) and the sensor wires. I then added gold-plated copper banana plugs. The plugs have holes in the side so that I could wrap the wires around securely and fill in the little cup with solder. Then I wrapped the exposed wires in stretchy electrical tape.
I was a bit concerned that the snap-in connections would be a point of high resistance and therefore high temperature. So I rigged up a single cell with a phone charger circuit board to see with my FLIR camera if there was a lot of heat at those snap-in points. This is ~0.7A draw off a single cell to a phone, which is 0.2C. That's not much, although if my motor actually operates at 250W, it will draw 0.35C, which is not too far off. Happily, I'm not seeing any hot spots anywhere, and the battery is only a few degrees warmer than the surroundings, even after giving it a few minutes to reach thermal equilibrium. The last picture is a pre-made battery charging pack, and the circuit board and USB plug are clearly getting a lot hotter. I am looking forward to testing the whole pack with the motor, but the throttle still hasn't arrived, and I'm still working on testing the batteries.
That's all I have for now. I will update as I can.
