Sticky PostThe On/Off Switch…the Nemesis of the DIY Electric Biker

May 9, 2015
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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?

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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

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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

cirquit breaker

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:

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Another solution would be to Buy a controller with an integrated LCD dash panel that has 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.

 

 Conclusion

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.

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A new ON / OFF switch now available

After this article came out, Luna Cycle searched for an existing option that they liked, and after a while a model became available in the spring of 2017 that they tested and felt they could put their reputation behind it.

When this electronic switch is off, it does not draw any current from the battery. This way, if your ebike is stored over the winter (or for a long time for any reason), the switch will not drain down your battery.

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The Luna Cycles electronic ON / OFF switch

 

The reason they looked for an electronic switch is because…a mechanical switch can be accidentally welded permanently into the “ON” position from a voltage spike, or temporary high currents on a high-performance system. The problem with common and readily available FET-based switches is that they have a low current drain when the switch is in the off position.

This switch is plugged-in between the battery and controller, and it has a remote ON/OFF button that can be located anywhere on your ebike. Some common controllers have two wires that can be used to mount an ON/OFF switch onto the handlebars, but again…this common style allows a slow drain on the pack when it is parked.

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Eric Hicks, May 2015

 

 

Eric has been involved in the electric bike industry since 2002 when he started a 6000 square foot brick and mortar Electric Bike store in downtown San Francisco. He is a true believer that small electric vehicles can change the way we operate and the way we think.

16 Comments

  1. I saw a cool switch setup. It’s a bit hard to explain, but I will try. The guy used a double pole knife switch with 4 contacts setup so the first 2 contacts the knives hit when switching on are for a precharge circuit, and when thrown all the way it is fully on. It is a steam punk style bike and it looks good. The owner is a machinist so fabricating it was not a problem for him.

    I am presently looking for a 4 pole double throw 30 amp switch so that I can charge in parallel with my RC charger and run in series. Sounds easy don’t it, but no. I have found one online but the prices vary from $20 to over $50 for what appears to be the same switch. I think I’ll go with the one from McMaster Carr if I can’t get one locally. I do prefer to touch stuff before I buy it.

    • show us a link to your switch if you find one..sounds interesting.

      • McMaster-Carr part number 8001K28 4PDT switch. It’ll work if I don’t use full power.

        Just got it today the specs on it are very conflicting.
        The catalog spec is.
        25A @ 125 V AC
        20A @ 30V DC

        The switch itself has these specs on one side.
        18A @ 125 V AC
        9A @ 250V AC

        The other side has these Specs.
        25A @ 125 V AC
        9A @ 250 V AC

        I don’t trust it at all having melted a 30 amp toggle with a 30 amp controller in the past. It will have to do till I get something better. I’ve Only been looking for about 3 years now. It is a lot of bother to go through just to keep from having to buy a new charger. I like my iCharge 208B.

        • thanks for that

  2. The author here is posting from fairly limited experience with garage style ebike builds where safety is 3rd and an accessible power switch is hardly on the radar of priorities. In that case yeah, there are too many people with ghetto plugs as their sole shut down mode.
    But contrary to the tone of the article, most vendors selling complete conversion kits includes nice on/off control, either in the battery pack or in the motor controller. So if Golden Motors sells a system with an on/off switch in their battery pack, why should they also have a redundant 2nd on/off switch in the controller too? It doesn’t hurt, but too many switches can get confusing too.

    Similarly, Allcell does make batteries with on/off power switches and an enclosure and all that, it’s called their Summit series and is what you should get if you want a full pack solution. Their Naked packs are meant to be a bare-bones power module for OEMs, who naturally have their own on/off control and wouldn’t want this as part of the battery in the first place. It’s not like they “could not think of” adding a switch, it goes against the very design intent of a minimalist OEM product.

    And of course the Cycle Analyst is meant to turn on and off with the controller power, so when you turn off your bike either via a controller switch or a battery switch, then the CA shuts down as well. A small switch to turn it off independently of the bike isn’t a terrible idea, but it would also give the illusion that a bike is shut down and turned off when it is not. If the controller is still plugged into the battery, it will be draining upwards of 500-1000mAh per day from the pack, and that’s the cause of more premature lithium battery deaths than anything else (getting left plugged into a controller).

    • Thanks for your input Justin. Most high power DIY ebikes do not use complete kits and no kit i know of comes with a Cycle Analyst. Since many high power ebikes use a cycle analyst, I would really like to see you implement some kind of throttle off or on/off switch in the cylcle analyst in future versions…or some type of audible or flashing warning when a bike is obviously not being ridden but the power is still turned on. The cycle analyst is obviously not a product for kit buyers…so therefore it should not be assumed that the components non-kit buyers are buying have an on-off switch somewhere…because most dont.

      The cycle analyst is conveneintly located on the handlebars…which would be a perfect place for an on/off switch…and i know you have the capacity to add this function if you saw the need.

    • Hi Justin,
      I don’t know if you’ll see this, but if you do, is there an easy way to prevent that kind of battery failure, without having to unplug the battery from controller? (some kind of switch?)

  3. This is Paul from EM3ev.
    We do have a power switch on all our controllers, it is included with all our kits and is an option with the bare controller. It does not require any soldering or plugs to be changed. The switch powers on/off the low power supply to the controller. It would also be very straightforward to use your own switch contact, anything would suffice, as no real power passes through the switch, nor is it a capacitive load, so there is no spark to wear out the contacts. If you put a switch in-line with the main power supply to the controller and switch the capacitors in and out, the switch will quickly wear out and fail. Once the supply voltage gets quite high and with larger capacitors being charged, a proper pre-charge circuit is required, which is what we fit in all out battery packs, which do not also have a switchable output.
    Grin’s Controller has a switch on the case AFAIK. if their controller is powered down, it will also power down their Cycle Analyst (same with our EM3ev controller), they do the same thing as us, disconnect the low power supply to the controllers control electonics. The only difference is that they have a case mounted switch, whereas we use a remote switch, functionally, they are exactly the same.
    Thanks
    Paul

    • Hi Paul…thanks for responding.

      Its good news that an on off switch is included in your kits that cost over $1000. 00.

      So an on off switch is a an option on your basic controller? What is the up charge for your on/off switch? There in china wouldnt it cost you just a few dollars to include one for free? Why is an on/off switch not included for free on a controller that cost over $150 retail? I happen to have one of your brand new bare controllers in front of me…why do you not include any instructions on how to hook up this on / off switch? Or any instructions at all for that matter? Couldnt you follow grins lead and have a case mounted on/off switch on your controllers at no extra charge?

  4. The on/off switch on many ebikes does not really disconnect the battery but only shuts down the computer, disabling the bike. This is how many things like TVs and cars work. In the case of the ebike this type of soft shut off can allow the battery to continue to drain causing damage to the expensive battery pack when the bike is left unused for long periods of time. Additionally the lack of a real shut off switch prohibits disconnecting power quickly if the throttle is stuck on or a short circuit is causing wires to burn. DIY bike have definitely been lacking in convenience, safety and reliability. The lack of on /off switches and other deficiencies are compelling reasons for many consumers to buy a “turn key” manufacturer ebike and skip the DIY.

  5. I picked up a circuit breaker from West Marine. 65VDC and 30A. They have them up to 50A.

  6. With high voltage and amperage flowing through these things, isn’t a relay the right thing to use?

  7. The flaw in the logic here is that you don’t want all the power going through the switch, but you do want that switch to physically disconnect the battery from the controller.
    I think the best setup is a DC contactor. It’s like a relay but the input side can take direct input from the battery (even up to 84 or 100V). Most relays have limited coil voltage (12V, 24V etc.). This is the solution proposed by Kelly Controllers and you can find pictures and schematics of this setup on their website. Basically the switch on the bike can be low amp (0.25A) and it switches the coil on the contactor which connects the battery to the controller. This is a safe cut off as turning off the switch will disconnect the battery from the controller. They are a little heavy, but do 150A. Another solution is to use an SSR which has input up to 32VDC and can do over 100A depending on the model. You would need to rig up something like a 12V DC-DC converter, but it’s lighter and who doesn’t like di

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