Try to build my first ebike

Deleted member 4366 · Aug 22, 2012

The Q100 will try to do about 20 mph with a KU63 controller using the high position on the three speed switch, but it doesn't really have enough power to hold that speed unless you're a light-weight. It's a bit gutless - especially at low speed. It works better in smaller wheels to get more torque. You need to get the current up to about 18 amps to get 20mph, which means soldering about half the shunt in the controller. With 48v, it will try to do about 27mph, but doesn't have enough power for that, so you'll be wasting a lot of battery and risk over-heating the motor if you push it too hard. A good compromise is 12S lipos (nominal 44v), which is half way between, but you need to know how to charge and look after them.
I think 48v is not necessary unless you want to use high power with a higher power motor.

The Bafang SWXK5 front or QWSXH rear are better if you want to travel at over 20 mph because they have a bit more torque, and they will run at 20 amps. They are a bit noisier and rougher than the Q100, but still OK. If you want to go continuously 20mph or more, you need the BPM motor.

Personally I don't like those racks because they look ugly. I prefer a light-weight normal rack and then put the battery in a football boot bag for which you make a thin plywood base and bolt it to the rack; however, this is not very secure if you want to leave your bike unattended for extended periods. You can also put your controller in the bag and some tools etc. See the photo below for an example.

I've made eleven orders with BMSBattery for a total of $3700. Most of the time you get what you ordered, but sometimes there's surprises. Overall I've been happy apart from when they try and bump up the shipping cost when they're ready to ship. I only paid one time out of three and they still sent my orders the other times, but it causes delays. It normally takes two to three weeks from ordering to receiving stuff. You could give Electric bike kit, lithium battery, lifepo4, hub motor, controller, bike parts-GreenBikeKit online store for electric bicycle components-GreenBikeKit.com a try. They have the same stuff. I'm guessing that someone defected to start up on his/her own.

Deleted member 4366 · Aug 23, 2012

Ask as many questions as you want!

BMSBattery will probably build the motor into a rim if you ask them. They used to supply them as a kit, otherwise get the rim and spokes from them as they're very cheap. It's not difficult to build a wheel with the many on-line guides, or you can get a bike shop to do it, but they often charge a kot. 13G is the thickness of the spokes, which is a bit thicker than those used on a non-electric bike, but pretty standard for a hub-motor bike.

For 20 miles each way, you need at least 15aH at 36v. I used to just about manage 15 miles each way (without re-charging) on a 10aH battery and SWXK5 motor, but I had to pedal hard. Then I got a BPM motor, which made me lazy, so now I use beween 9 and 12aH.

Deleted member 4366 · Aug 24, 2012

I haven't used Greenbikekit yet, but I will next time. As far as I can see, they're an off-shoot from BMSBattery. It appears that their shipping costs are less. This is there 250w controller for the SWXK5. You can get it with the handlebar panel (equiv. to KU65) or without (KU63).
motor controller 36V250W for e-bike brushless dc motor-GreenBikeKit online store for electric bicycle components-GreenBikeKit.com
You should try it as standard first, and then, if you want a bit more power solder the shunt like this. Best done with a watt-meter to see the results:
Before

After

Deleted member 4366 · Aug 24, 2012

Forget that case for the controller unless you're very neat at tying down wires. I couldn't get my controller and connectors in there. I know someone who managed it, so it must ne possible, but the wire's too stiff, which makes it really difficult. If you're going to put the battery in a bag/box, stick the controller in there too. It's much easier and neater.

Those throttles break when you're holding full throttle and go over a bump. Then it's left at half throttle or whatever, so you have to ride home using the brakes as an on/off switch. Get the thumb throttle or a more expensive one elsewhere.

The controller uses the voltage drop accross the shunt to determine how much current it's giving. Adding solder to it reduces its resistance so less voltage drop and the controller gives more current. You can do this mod to most controllers to get better hill-climbing. Many ready-made ebikes are set to 12amps which would have me off and pushing up significant hills because of my weight. I can manage most at 20 amps, and by 25 amps I don't have to pedal. Don't forget 20 amps is the safe max for your motor, and for anybody else that want to try it, you also need to consider how much current your battery can give, so don't waste your time if you have an 8aH bottle battery or worn out other type. With the Headway battery you can go as high as you like.

Deleted member 4366 · Aug 24, 2012

I'd go for the 20 - 40 amp BMS in case you want to use it for something else later. Also it'll probably allow you to charge it faster too, which reminds me. I think you have to order the charger separately. The 120w should be OK unless you need to charge in a hurry.
Alloy charger for lifepo4, lead acid battery and lithium battery, 120W charger online store for electric bicycle components-GreenBikeKit.com

Deleted member 4366 · Aug 25, 2012

You don't need to buy a separate BMS. The battery already has one. The standard one gives 20 amps, but you can pay an extra 15 to upgrade it to 40amps by selecting from an options box on the item listing between the picture and the Product Description.

Deleted member 4366 · Sep 28, 2012

Looks good to me, but I think 18mph will be the practical top speed.

NRG · Sep 29, 2012

Well there you have it, up the voltage....or go for a higher RPM motor with a higher amp controller to regain climbing ability. You will also need to look at gearing to be able to assist the motor at that speed, however, speed increase follows a cube law so to double the speed for instance takes quadruple the power. So factor in an increase in power delivery to the motor along with an increased voltage.

banbury frank · Sep 29, 2012

Hi Pat Try the links below looks just what you need

Bafang 48V**BPM**500W Rear** Ebike kit - Elifebike Online Store

48V 10AH LiFePO4 Alloy Shell Battery Pack For EBike - Elifebike Online Store

I will add I recommend Rear Motor because with this power the rear off the bike is much stronger also in the wet the front motor can spin out off control this is a serious bit off kit for climbing hills

Frank

Scimitar · Sep 29, 2012

36V 15AH HEADWAY LiFePO4 Battery Pack DIY kit for ebike - Elifebike Online Store
This looks interesting.

Deleted member 4366 · Sep 29, 2012

Scimitar said:
36V 15AH HEADWAY**LiFePO4 Battery Pack DIY kit for ebike - Elifebike Online Store
This looks interesting.

I have the 12aH version from BMSBattery. It's a very strong and robust battery, and it never goes below 39v even when nearly empty.

Try to build my first ebike

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