Electric moped cafe racer

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vagosofron

100 W
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Dec 16, 2017
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After building my single speed ebike ( 250w front hub motor 36v), i realised that i need something faster and more comfortable. I'm considering electrifying an old yamaha jog 50cc i have laying around, or find a small frame and build a really cool cafe racer, like the onyx rcr which i really like.
I want 40 miles of range and 60mph top speed. What motor/esc/battery do i need to get those numbers? I would prefer a hub motor on both cases, because i don't want to mess with chains. I know that, scooter or cafe racer, it will take a lot of work to make it work, but i have time.
The ebike project was simpler, because after a lot of searching i found out that i needed a hub motor conversion kit, so i bought one and installed it myself. This project though, is more complicated and i need some help to identify what hub motor ( how much kw), what esc and what battery ( how many volts and ah) are needed.
Thank you all in advance, Evan.
 
To maintain 60mph, you'll need at least 7000W at the wheel, at that speed. Depending on the style of bike and the riding position, you might need substantially more. Taking into account electrical losses, you would need at least 6kWh of battery to maintain 60mph for 40 miles. You wouldn't need that much to go 40 miles at a lower speed.
 
I don't want the 40 miles range while traveling at top speed, just normal in city riding. I guess i wouldn't mind a 50mph top speed. So what voltage do you suggest? Are 72v enough? And are those generic escs suitable for this?
 
vagosofron said:
I don't want the 40 miles range while traveling at top speed, just normal in city riding. I guess i wouldn't mind a 50mph top speed. So what voltage do you suggest? Are 72v enough? And are those generic escs suitable for this?
Click to expand...

For 50mph, you'll need about 4kw (wheel) at a minimum. That's easier and cheaper. 72V is a good working voltage for reasonably cheap equipment in that power range. You'll need at least a 75A controller to get into that power category. It doesn't have to be fancy; it only has to deliver the watts you need.

Others will have better ideas about what motors might work best for 4kW at 50mph. That's higher power than I'm familiar with.
 
vagosofron said:
What about the battery's capacity approximately?
Click to expand...

1000Wh to ride 30 miles at 30mph
2000Wh to ride 40 miles at 40mph
4000Wh to ride 50 miles at 50mph
 
vagosofron said:
5000wh, so it has to be a 50ah battery pack, am i wright?
Click to expand...

???

Watts are power.
Watt-hours are battery capacity.
A 72 volt battery with 50 amp-hours of capacity contains 72 x 50 = 3600 watt-hours.
 
Also, keep in mind that a particular speed at a particular wattage would be on the flats, no wind. ;)

If you have a headwind, then your speed will drop by the windspeed amount, approximately.

Similarly, speed would drop on hills depending on vehicle+rider/etc weight and the hill slope.


Battery capacity needed for any specific range will also be affected by the above.


So if you ride in conditions other than still air and flat ground, you might need more power and/or more battery capacity.
 
Chalo said:
vagosofron said:
5000wh, so it has to be a 50ah battery pack, am i wright?
Click to expand...

???

Watts are power.
Watt-hours are battery capacity.
A 72 volt battery with 50 amp-hours of capacity contains 72 x 50 = 3600 watt-hours.
Click to expand...
Ok, got it. So if i want to determine how many sels i need for that battery, how do i do it? It will be a 20s?p.
Sorry for the trouble.
 
vagosofron said:
Ok, got it. So if i want to determine how many sels i need for that battery, how do i do it? It will be a 20s?p.
Sorry for the trouble.
Click to expand...

The cells you use will have an amp-hour rating depending on their size and chemistry. So if you need 50Ah of capacity, and your cells are 2200mAh, then you would need to use 50 ÷ 2.2 = 22.7 cells in parallel (so 23P). If you're using big 25Ah prismatic cells, then you'd only need 2P.
 
Chalo said:
vagosofron said:
Ok, got it. So if i want to determine how many sels i need for that battery, how do i do it? It will be a 20s?p.
Sorry for the trouble.
Click to expand...

The cells you use will have an amp-hour rating depending on their size and chemistry. So if you need 50Ah of capacity, and your cells are 2200mAh, then you would need to use 50 ÷ 2.2 = 22.7 cells in parallel (so 23P). If you're using big 25Ah prismatic cells, then you'd only need 2P.
Click to expand...
So i guess there is no easy answer to this :? .
And since this wont be a conversion kit that encludes everything, i will have to find the motor and controller first and then buy/build a battery. Thanks for the help. I will come back with more questions :p
I saw the ecub from a company called shanghai customs and loved it. I will try and build something like that.
 
YOu'll probably want to read at least a few of the many threads about the different kinds of cells, and packs built for higher power usage.

Different cells have differetn capabilities, so which ones you use will determine how many you need.

Some cells are higher capacity, and some are higher C-rate (capable of higher currents). Some are a compromise between the two.
 
amberwolf said:
YOu'll probably want to read at least a few of the many threads about the different kinds of cells, and packs built for higher power usage.

Different cells have differetn capabilities, so which ones you use will determine how many you need.

Some cells are higher capacity, and some are higher C-rate (capable of higher currents). Some are a compromise between the two.
Click to expand...
Yes i realized that these kind of projects require a knowledge that i don't have, but I'm learning, thank you.
 
It can get pretty complex, depending on how far into the DIY stuff you want to get. :/

I've been here a decade, reading almost every day, and still learn new stuff every day! :oops:
 
60mph on a Yamaha Jog? Forget it. Even if you CAN find the fast hub to fit, not sure it's out there, but that's not the bike to be going that fast on. The Onyx would be dicey. Just build your plans around a solid platform.

https://www.aliexpress.com/item/Bluetooth-72v-8000w-QS-273-electric-bike-hub-motor-conversion-kit-with-TFT-colorful-display/32881656316.htm
 
Dauntless said:
60mph on a Yamaha Jog? Forget it. Even if you CAN find the fast hub to fit, not sure it's out there, but that's not the bike to be going that fast on. The Onyx would be dicey. Just build your plans around a solid platform.

https://www.aliexpress.com/item/Bluetooth-72v-8000w-QS-273-electric-bike-hub-motor-conversion-kit-with-TFT-colorful-display/32881656316.htm
Click to expand...

Yes, i was crazy thinking about converting that jog :oops:
The honda c50 is a solid platform. Thanks for the link, but i have to order from Europe, due to customs taxes here in Greece, so i will keep looking. Anyway, this project is going to take a lot of time to complete, so i will take my time.
 
What you are looking for is pretty close to a Sur-ron Light Bee. My Sur-ron tops out at 42mph. You could make it go faster by changing the gearing, but range would drop a lot. If I go fast on mine, I can get about 25 miles range with the stock battery. The Sur-ron battery is supposedly 60V, 32Ahr (16s, 11p).

I'm in the process of building a secondary battery for mine, which will double the range.

 
vagosofron said:
I love that bike! That and the Onyx RCR, but both are out of my money league!
Click to expand...

Then you need to lower your goals of building a safe 60mph, 40 mile range bike.
Or see if you can buy a decent second hand electric scooter/moped and upgrade that one step at a time (better battery and controller at higher voltage, etc.).
 
That's a good suggestion. I've seen some pretty nice electric scooters for sale really cheap when their lead acid batteries died. Upgrade to lithium and have something decent for a very reasonable cost.
 
I think in order to stick with his goal he has to source a good cheap donor bike that he can cash in on some parts that come off , which then might convert on under $1k added on, before the battery.

Maybe people can start estimating his battery, bms charger. . .
 
My donor mopped is a honda c50. I can't sell anything from it, because it's not working. I will sell my ebike to raise some extra cash, but since this is a slow building project, i will have enough money to get the parts i need in the long run. It doesn't have to be a 60mph top speed bike, i can live with 50mph :) .
 
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