regenerative e-bike

Thread Starter

wmich

Joined Feb 13, 2012
1
hi
this is the first time for me to join this awesome forum

my senior project is regenerative e-bike that I use the brake system to recharge the battery again
I bought all stuff like the hub motor that is 35V 750 watt also I want to use DC DC converter to step up (boost)
my questions
is dc dc converter goin to be helpful?
also I dunno how to choose the exact values of resistors its my fist project and I got confused how can I choose needed resistors or capacitors
my battery is L-Irion phosphate and my controller is adruino uno
please I need ur advising and help to go step by step to understand and finish this project
by the way I also use relays to control the path of the motor and the battery

thanx in advance
 

shortbus

Joined Sep 30, 2009
7,078
What you want is called "synchronous rectification" or two quadrant motor drive. A Google search will get you information on it. I'll give a head start for you-

While this link is mainly for switch mode power supplies it explains the working of sync/rectification- http://scholar.lib.vt.edu/theses/available/etd-173510281975580/unrestricted/chapter2.pdf

Here is a good one on two quadrant drive- http://www.physicsarchives.com/index.php/courses/472

Relays will not switch fast enough for your application. Your best bet is mosfets, for your motor control. There are a lot of circuits on the web for this, have fun and welcome to AAC!
 

Audioguru

Joined Dec 20, 2007
11,251
I laugh when I see an e-bike creeping along the road with cars flying past. The e-bike has very dim lights that can barely be seen at night.
They should be banned.

Some people ride a Vespa skooter. It has enough power to keep up its speed with other vehicles and has bright lights. I laugh when I see one when it is raining.
 

MrChips

Joined Oct 2, 2009
19,382
That's a well written article but it took a lot of physics research and words to say what was fairly obvious - regenerative braking or power generation going downhill just isn't worth it.

btw, I am an ebike rider myself. I hope you don't laugh at me on my ebike.
 

MrChips

Joined Oct 2, 2009
19,382
That link shows one of the reasons why the "hard-core" E-bikers don't use a 'hub' motor. They also have 'free-wheels' (one way clutch/bearings) between the motor and wheel.
Not sure what you mean by that. The vast majority of ebikes are driven by brushless DC (BLDC) drive hub motors. The electronics to drive the motor is very interesting, not unlike the motor drive on a hard disk drive. It uses power MOSFETS and Hall Effect sensors.
 

shortbus

Joined Sep 30, 2009
7,078
They have a one-way bearing at the motor sprocket. That way the motor doesn't cause drag when just pedaling or coasting. It also won't cause problems from regeneration in the motor then. Without the one-way bearing or 'free-wheel' the rotor generates a voltage and can cause problems with the motor controller.
http://en.wikipedia.org/wiki/Sprag_clutch
 

GetDeviceInfo

Joined Jun 7, 2009
1,642
we do a lot of product/process development with one client. They have big ideas and a fairly large budget, but I always recommend that they prove the basics on simple rigups, before committing to major expenditures. In this case, a possible suggestion would be to prove your concept on a simple flywheel. Accelerate your mass then decel with your regen, then accel, etc, carefully measuring for any power that 'circulates' and it's eventual loss. Transferring to the bike from there should just be a case of arresting the power 'thiefs' that accelerate the loss, if that's anywhere close to possible.
 

THE_RB

Joined Feb 11, 2008
5,438
Generally the consensus it that bicycles are used on flat roads and gentle gradients, where freewheeling is comon for a lot of the riding time and the biggest energy efficiencies come from a low-drag freewheeling system.

Stop/start riding (traffic) can be good for regenerative braking in cars as they are very heavy and can also carry the additional complexity of equipment to try to increase regenerative braking efficiency. But bikes are light, and stop/start use generally comes with some pedalling anyway, and the best performing bikes at this point use small lightweight batteries and motors and maximised freewheeling time.
 
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