Possible to build an electric foldable bike?

General Discussion about electric bicycles.
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shawnanderson   1 µW

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Possible to build an electric foldable bike?

Post by shawnanderson » Dec 03 2012 11:16am

If I have a foldable bike, can I buy any kit to build one? It has to follow Singaporean electric bikes rules.

Thanks. Recently getting interested in an electric bicycle but I am a noob in this. =)

Singapore Rules
Riders of motorised bicycles must comply with the following requirements:

The construction of a motorised bicycle must be similar to that of a conventional pedal bicycle;

It must be powered by an electric source i.e. not petrol driven;

Its motor's maximum power output must not exceed 200 watts;

The electric motor can only cut in when the rider starts to pedal; and

The electric motor must cut off when the bicycle reaches a speed of 25 km/hr or when the rider stops pedalling. This speed is comparable to the average speed of a moderately fit adult pedalling a conventional bicycle on level ground;

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Jeremy Harris   10 GW

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Re: Possible to build an electric foldable bike?

Post by Jeremy Harris » Dec 03 2012 11:36am

The answer is probably yes, depending on the frame of the bike. Some folding bikes have frames that are difficult to fit a hub motor too, as the spacing between the forks or rear drop outs is too narrow, others are fine. Wheel size is also important, as it's fairly easy to find a hub motor that is suited to a 20" wheel, but slightly harder if your bike uses smaller wheels.

To meet your regulations there are several small hub motors you could use, depending on whether you wanted the motor at the front or the rear, and whether you wanted a wide gear range or would be happy with maybe 6 or 7 gears. To be legal you would need to fit a pedelec sensor to the pedals, but this is fairly easy as long as the folding bike you have in mind uses a standard bottom bracket (many do). You would also need a pedelec capable controller, but these are both readily available and fairly cheap.

As you're in the Far East, I'd suggest taking a look at the kits available from Greenbikekit http://www.greenbikekit.com/index.php/e ... kit-1.html

Many kits on that link will meet your needs. For example, this front wheel kit: http://www.greenbikekit.com/index.php/3 ... e-kit.html includes the pedelec sensor (PAS) a suitable controller and is available in a 20" wheel. You would need to add a battery pack of your choice, and get a charger, but assembly would be fairly easy if you're already happy with working on bikes. Alternatively, there is a rear wheel kit available: http://www.greenbikekit.com/index.php/3 ... e-kit.html if you prefer rear wheel drive (I personally do).
Please ask questions on the forum, rather than by PM, as it helps others and you'll get a better range of answers.

melodious   100 kW

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Re: Possible to build an electric foldable bike?

Post by melodious » Dec 03 2012 12:59pm

With those restrictions you can either 1. place an electric motor in the front fork or 2. place an electric motor in the rear dropouts. Front forks for folders come in 100mm or 80mm widths. The rear dropouts can usually measure between 100mm or the standard 135mm.

I have a q85 front motorkit (motor in a spoked wheel, controller, pedal assist option and/or throttle, electric cutoff brakes) bought off BMSbattery.com at a reasonable pricepoint. It fits snugly within an 80mm front fork. It will accept 24V, 36V, 48V battery configurations. I bought a 36V battery and it gets a leisurely paced speed, although it's not going to blow the hair off your head. What it does well versus a nonmotorized bike are the hills. It's like there's a person pushing behind you helping you to climb. You come out of it more relaxed and with more stamina and less winded. As a daily commuter, it's a boon.

The q100 is almost the same motor but fits into a 100mm front fork (standard width fork for most bikes). It's rated, however, at 300-350W, which is considered illegal. I'd still use it if I had a 100mm fork. I highly doubt a motor that size would bring any suspicion to police, unless your being wreckless and potentially harming pedestrians. That's my 2 cents...

"You have to learn to crawl before you can walk". I believe most of us here after some time just get bored of their legal setup and venture into faster and more powerful battery/motor combinations. After learning what I have from my first setup, I'm about to embark on the faster side of things... :P
Surly Ogre rigid 29er, rear 10T MAC @ 50V 25AH & 40A: 30mph road/gravel/hill machine
42" dual diagonal Eskateboard @6s & 90mm wheels
Next: eMTB @10-12s & 8"-12" pneumatic wheels; Got Strapped? d-(',')z

shawnanderson   1 µW

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Re: Possible to build an electric foldable bike?

Post by shawnanderson » Dec 23 2012 7:59am

Thanks for the info! From the website, it seems like the smallest power output is still 250 watts which exceed Singapore Rules. In order to use an electric bicycle here, your bike need to be certified by local regulator (otherwise you will be fined). Singapore is a "fine" country. You will get fined for not even flushing the public toilet. haha...

Jeremy Harris wrote:The answer is probably yes, depending on the frame of the bike. Some folding bikes have frames that are difficult to fit a hub motor too, as the spacing between the forks or rear drop outs is too narrow, others are fine. Wheel size is also important, as it's fairly easy to find a hub motor that is suited to a 20" wheel, but slightly harder if your bike uses smaller wheels.

To meet your regulations there are several small hub motors you could use, depending on whether you wanted the motor at the front or the rear, and whether you wanted a wide gear range or would be happy with maybe 6 or 7 gears. To be legal you would need to fit a pedelec sensor to the pedals, but this is fairly easy as long as the folding bike you have in mind uses a standard bottom bracket (many do). You would also need a pedelec capable controller, but these are both readily available and fairly cheap.

As you're in the Far East, I'd suggest taking a look at the kits available from Greenbikekit http://www.greenbikekit.com/index.php/e ... kit-1.html

Many kits on that link will meet your needs. For example, this front wheel kit: http://www.greenbikekit.com/index.php/3 ... e-kit.html includes the pedelec sensor (PAS) a suitable controller and is available in a 20" wheel. You would need to add a battery pack of your choice, and get a charger, but assembly would be fairly easy if you're already happy with working on bikes. Alternatively, there is a rear wheel kit available: http://www.greenbikekit.com/index.php/3 ... e-kit.html if you prefer rear wheel drive (I personally do).

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Jeremy Harris   10 GW

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Re: Possible to build an electric foldable bike?

Post by Jeremy Harris » Dec 23 2012 8:25am

shawnanderson wrote:Thanks for the info! From the website, it seems like the smallest power output is still 250 watts which exceed Singapore Rules. In order to use an electric bicycle here, your bike need to be certified by local regulator (otherwise you will be fined). Singapore is a "fine" country. You will get fined for not even flushing the public toilet. haha...
You can reduce the power fairly easily if you use a programmable controller, rather than the one in the kit. For example. the Xiechang range of controllers (sold by many vendors, but as you're in the Far East I'd suggest contacting Keywin in China) can be connected to a PC and programmed to reduce the current limit and maximum speed very easily. This reduces the maximum power, so you can then adjust the controller to meet your local laws. Keywin sells controllers on ebay, and one like this: http://www.ebay.com/itm/36V-350W-brushl ... 3cc1aea6c0 can accept a pedelec sensor input and be programmed to lower the power down to the level you need.

The programming and wiring of the programming interface to a PC will need you to get inside the controller, but there is a great deal of knowledge here on doing this, as well as an open source programme that you can use to change the controller setting safely and easily.
Please ask questions on the forum, rather than by PM, as it helps others and you'll get a better range of answers.

shawnanderson   1 µW

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Re: Possible to build an electric foldable bike?

Post by shawnanderson » Dec 23 2012 8:30am

Thanks for the info. Quite interested in the q85. How do we know that the speed will cut off when it reached 25km/hr? For the battery, is there a combination of volts and Ah I have to buy with this motor?

melodious wrote:With those restrictions you can either 1. place an electric motor in the front fork or 2. place an electric motor in the rear dropouts. Front forks for folders come in 100mm or 80mm widths. The rear dropouts can usually measure between 100mm or the standard 135mm.

I have a q85 front motorkit (motor in a spoked wheel, controller, pedal assist option and/or throttle, electric cutoff brakes) bought off BMSbattery.com at a reasonable pricepoint. It fits snugly within an 80mm front fork. It will accept 24V, 36V, 48V battery configurations. I bought a 36V battery and it gets a leisurely paced speed, although it's not going to blow the hair off your head. What it does well versus a nonmotorized bike are the hills. It's like there's a person pushing behind you helping you to climb. You come out of it more relaxed and with more stamina and less winded. As a daily commuter, it's a boon.

The q100 is almost the same motor but fits into a 100mm front fork (standard width fork for most bikes). It's rated, however, at 300-350W, which is considered illegal. I'd still use it if I had a 100mm fork. I highly doubt a motor that size would bring any suspicion to police, unless your being wreckless and potentially harming pedestrians. That's my 2 cents...

"You have to learn to crawl before you can walk". I believe most of us here after some time just get bored of their legal setup and venture into faster and more powerful battery/motor combinations. After learning what I have from my first setup, I'm about to embark on the faster side of things... :P

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Jeremy Harris   10 GW

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Re: Possible to build an electric foldable bike?

Post by Jeremy Harris » Dec 23 2012 9:06am

If you go for one of the cheap programmable controllers then you can build the bike, test it, and then reprogramme the controller to get the speed to the legal limit (max speed, as a percentage, is programmable, as well as the current limit). This means you can be sure that your ebike won't exceed 25km/h once correctly set up.

The other way to do it is to make a guess on what your likely maximum speed will be, and go for a non-programmable controller, like those on the BMS and Greenbikekit web sites. The downside there is that you may well end up with either an ebike that goes too fast for your laws, or one that goes too slow, and then there's not much you can do to change that except hacking about with the throttle and maybe tampering with the current limit components (neither of those options is as easy as plugging a programmable controller into a PC and just changing the settings).
Please ask questions on the forum, rather than by PM, as it helps others and you'll get a better range of answers.

melodious   100 kW

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Re: Possible to build an electric foldable bike?

Post by melodious » Dec 23 2012 10:53am

I have the q85 motor run on a 36V battery. The q85 has two versions, a high torque or a high RPM version. I have the high RPM version because the torque version would probably be too slow for my pedal cadence (probably a measly 10-12mph). I bought it as their 20" wheel kit. It fits on my front 80mm fork. It gets me 15-18mph on flat roads with no headwind. It also gets me up good hills with me pedal assisting it. I didn't get the torque version because it would always disappoint my pedal cadence. The bike will never get the attention of authorities because it meets the criteria for much of the world's legal speed limit for electric bikes. I don't worry when I ride by authorities; moreover, the authorities really don't do anything to me, as I'm mostly following the law. This is my goto bike for over a month now. I don't have a car. Not trying to persuade you in what motor/battery combination you should get. Just trying to provide you with information that I have concerning a motor your interested in.

I don't know how it handles 48v yet because I haven't made a battery with those voltages. I just got my GNG mid drive kit and it's rated for 48v battery/controller. I will eventually make a 48v battery using the DIY hobbyking LiPo bricks that so many here do. Once my new more powerful bike is setup you know it's only a matter of time before I try that same 48v battery on my small q85 motor! I have a good feeling it can handle it. Probably get me 3-5 more mph. Of course, since my LVC would be compromised from the new higher voltage, I'd have to rely on external readings to prevent an overdischarging event.
Surly Ogre rigid 29er, rear 10T MAC @ 50V 25AH & 40A: 30mph road/gravel/hill machine
42" dual diagonal Eskateboard @6s & 90mm wheels
Next: eMTB @10-12s & 8"-12" pneumatic wheels; Got Strapped? d-(',')z

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