As the editor of electricbike.com, I have ridden a massive amount of electric bikes both home-built and commercial ebikes. Here is a weird stat: 100 percent of the 100 or so commercially available ebikes I have ridden have an on and off switch…and I would estimate only 30 percent of the 100 or so DIY ebikes I have ridden have an on/off switch.
Nowhere is the technology gap seen more in DIY electric bikes than the ebike on and off switch, and nowhere does it seem more needed.
Why is an on/off switch so hard?
Usually an on and off switch would be easy. But most DIY ebikes are running a lot of amperage and this will stress a normal switch. If the switch is built into the controller it is no problem, since the controller is already equipped to deal with high voltage and amperage. The lower power the ebikes components, the easier it is to incorporate an on off switch. High powered ebikes require more thought because of their capacity to roast connections and switches.
If you use just a regular on/off switch on a high power bike, the high amperage will eventually “toast” it.
Ghetto Ebike Switch
Most of the DIY electric bikes I have seen/ridden are turned on by connecting a battery via an ebike connector manually plugged together. This can be pain. On a high-power bike, this usually makes a large sparking noise which bothers almost everyone and causes the connector to corrode and eventually fail. The connector fries after this frequent “arc and spark” maneuver, and the connector will require occasional replacement which means more soldering and more hassle. A faulty connector can leave you stranded on a long ride etc and adds to the unreliability of ebikes. Also because it is a pain to turn the bike on and off in this way, some ebikers just leave there bikes turned on, even when parking and this can be dangerous.
On /Off Switch for safety
An On/off switch is a pertinent safety feature on an electric bike.
Most home build DIY bikes are powerful and fast.
Some electric bikes can be noisy or rickety sounding at speed….but all ebikes have one big thing in common….they are silent when they are parked….on or off. A common problem is someone will grab a DIY ebike intuitively by the hand grip, and not realizing the bike is on, the twist grip sets off and the ebike launches (small kids that are just passing by are the most dangerous). As the bike powers up, the tendency is to grab the handgip (throttle) tighter and the ebike gets power juiced into the rear wheel, gaining more power as the startled person grabs the throttle tighter as a natural response.
Not having an on and off switch on most DIY bikes is a huge safety glitch, which is not only unsafe to the user, but potentially can be dangerous to someone unknowingly moving the bike, or to an innocent pedestrian.
A twist throttle and no convenient on/off switch is extra dangerous. A thumb throttle is a safer solution because of the problem listed above.
The Kill Switch…another Safety Factor
Some ebike safety nuts advocate the use of a kill switch in an ultra powerful home-built electric bike. This means that if something goes wrong in your electronics, and the bike somehow gets stuck on Wide Open Throttle (WOT), there is a way you can break the power to the motor (since most brake systems are not powerful enough to stop a high-horsepower electric motor) and bring you to stop quickly. In all my years riding electric bikes, it has been very rare that I have seen such a kill switch implemented in a DIY electric bike, but I would argue why not make a dual purpose on/off switch AND kill switch.
Simple On Off Solution for the DIY Builder plus Kill Switch
Here is one easy idea for an on / off switch for a DIY builder. Go with a circuit breaker rated for however many amps your running. This will not only serve as an on off switch but an emergency kill switch in case of a mishap.
Easier and cleaner solutions than a Circuit Breaker
Buy a Controller with an on and off switch that is already built-in. If you’re buying direct from China, an ebike controller can have an on and off switch installed on it for no more than 5 extra dollars…problem solved.
Many controllers have a couple of wires that can be wired for an on off switch. Figure out if your controller has that feature, and then you can wire an on off switch to your dashboard or hidden whereever your controller is hidden. Most Chinese on / off switches that interface with the controller are handlebar mounts such as this one:
Another solution would be to Buy a controller with an integrated lcd dash panel with an integrated on/off switch.
Some Chinese hub motor factories are smart enough to provide an integrated dash board with an on and off switch. This makes a convenient solution.
It seems like there are no easy off the shelf components to make adding a on/off switch to your DIY electric bike easy.
If you want one you will have to take the initiative to read articles such as these and decide how you will implement one in your system, or buy a controller or battery that has an on/off solution that is acceptable to you.
Eric Hicks, May 2015