Electric bicycle conversion - Page 1
Forum section: electronics / projects

author: TheAmmoniacal
author_rank: Unknown
timestamp: April 26, 2014, 12:35:21 pm
content: I have a pretty basic bicycle that has stood unused for a couple of years now, as I started university it was just too far (7.2 km) and with the inexpensive public transport the choice was easy. But recently I've been thinking of converting it to electric, technically equip it with a "support" motor. But I'm not exactly sure how to go about it, I guess some of you have done this conversion yourselves and have some experience to share? I also have some questions to ask.The law in this country states that the electric motor must not exceed 250 W (1/3 hp), and the effect "has to slowly decrease as the speed approaches 25 km/h, where it has to entirely cease".So my question is, would a hub motor be the only way to go (integrated in the wheel)? Or would it be a good option to mount it on the seat tube/chain stay and use it directly on the chain? In thise case, which motor technology would be the most suitable? 12V or 36V? (What about a 3-phase DC brushless motor?).Building a controller circuit is a bit out of my league, so if anyone can find good and inexpensive driver circuits (speed sensing/control to limit it to 25 km/h, a PWM for speed adjustment and maybe even reverse charging?).And when it comes to batteries, would three 12V 12Ah lead-acid (3x4 kg) batteries be a big drawback from a LiPo pack? (Series or parallel). Considering I already have a couple of those lead-acid batteries, it would be nice if they could be used.Just looking for some good feedback before I attempt to proceed with this project, and how much of it I can DIY vs. just getting a conversion kit.I apologize for any ill-informed questions and for my naiveté. I'm just a lay-person with little electronics experience.

author: Psi
author_rank: Super Contributor
timestamp: April 26, 2014, 12:39:01 pm
content: i'd probably go with a ready-made wheel/hub motor and some lipos from hobbyking.Not too sure about where to get a good ESC from. I expect the hubmotors are burshless DC outrunners. The high current hobbyking ESCs all say, not for use on bikes/carts/ etc.. but it maybe just a timing incompatibility thing.

author: digsys
author_rank: Unknown
timestamp: April 26, 2014, 01:33:32 pm
content: FIRST of all, you don't state what country you're in !! IF you're an aussie -There are many of our members who own / import / refit / manufacture / convert / repair ALL type of electric bikes / motorcycles / cars.You can start athttps://www.facebook.com/groups/ev.melb/and search through the posts and links. There are also a few organisations,including ATA, AEVA, Swinburne etc that have active membership. Swinburne recently had their EV Expo, and several EV bicycle suppliers,converters had a stand. It's all in / linked in that FB site.IF you're not in aussie, then I KNOW that there are MANY similar options in every country. You can DIY, buy a kit or ready to go.

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: April 26, 2014, 01:47:17 pm
content: some points:7.2 km one way is not a long commute, its perfect bike range.If you live in a flat country then get a hub motor, steep hills a bottom-bracket motor which drive the rear wheel through your chain and get the benefit of gearing.Stay the hell away from lead acid they are the worst possible option, you want something like this LifePo:http://em3ev.com/store/index.php?route=product/product&path=35&product_id=158That store is run by an Englishman (paul) in China, a good guy he will set you straight, although he might take a day or two to respond to email.join the endless-sphere forum, lots of knowledgeable help there.

author: dannyf
author_rank: Super Contributor
timestamp: April 26, 2014, 02:34:22 pm
content: I haven't seen people doing this so I am dashing the hopes of anyone patenting it.I would put a motor right on top of the rear wheels and driving the rubber tube. The motor can be mounted on a frame, with one end of it attached to the frame, just under the seat, and another end attached to two rods mounted to the rear axel.A structure like this allows the motor assembly to be ported from bike to bike, in seconds, with sanp-on locks.

author: Codemonkey
author_rank: Regular Contributor
timestamp: April 26, 2014, 02:55:15 pm
content: Quote from: dannyf on April 26, 2014, 02:34:22 pmBeen done already, numerous times:http://www.electricbike.com/friction-drive/

author: miguelvp
author_rank: Super Contributor
timestamp: April 27, 2014, 01:15:47 am
content: better yet, google:"drill powered bike"