Build An Electric Motorcycle

On the list of things we’ll build ‘when we get a few free weekends,’ an electric motorcycle is right at the top. With a 20-mile range, they may not be as  versatile as a car or truck, but we can’t imagine a vehicle better suited for making a quick jaunt around town. [Ben Nelson] just finished his electric motorcycle and put up a great Instructable on converting an ’81 Kawasaki KZ440 to battery power.

After going over the rarely mentioned aspects of license, registration, and insurance, [Ben] started his build by pulling the engine from his bike and installing an electric motor. The batteries used weren’t insanely expensive LiPo cells, but instead cheap lead-acid units. The calculated range with the lead-acid batteries was 26 miles – perfect for a trip to the next town over and back.

After everything was cabled up, chain wrapped around sockets, and an awesome yellow paint job applied, [Ben] finally took his bike for a test drive. Check out the videos after the break for an idea of how fast [Ben]’s bike can go.

46 thoughts on “Build An Electric Motorcycle

      1. My Kawasaki KZ440 is geared for 45mph. I live right outside a city, where it’s all 25mph streets. A simple gear swap would take top speed up to 65, without any other changes, but would loose a little of the low-end-torque.

  1. 1) awesome conversion!
    2) i wanna ride it!
    3) i want the money to buy the batteries to make one! EDIT: and the bike!

    4) one little glitch that doesnt affect your prototype at all though :) …
    Lead-Acid battery on it’s side?
    in series or parallel?
    if they are in parallel, then one day,
    after about 2 – 10 years,
    and if theres no giant fuse…
    the sideways one might short-out causing them both to get angry…

    but awesome bike none the less, the battery can always be flipped around after a good summer’s worth of fun! :)

    PPS: yes i know you can use an SLA on its side, but life is greatly reduced, esp. if charged that way. the “Sealed” thing is more of a tipping it over kinda thing, it still wants to be upright most of the time.
    i was told this by someone that stood to profit greatly if i was to use it sideways and kill it early, wow honest salesman.

      1. He wasn’t referring to accidental leakage.

        He’s concerned about the sulfate/desulfate pattern causing unnecessary wear on the battery’s internals due to being mounted sideways.

        In my experience, most batteries are designed to be vertical 90% of the time. Due to this expectation, the internal plates are arranged to have the most plate/acid contact when arranged vertically.

        The internal casing on cheaper sla batteries will often use thinner materials on the top surface as well.

        Mounting one of these cheaper batteries sideways can cause the thinner top plate to wear down over time, causing leakage.

        Additionally, if the battery has uneven sulfate buildup, it is possible for an internal short to form along the “top” of the battery.

        It takes years of constant charging/discharging, but I have seen sla batteries in badly installed battery backups eat through the top of the battery.

        The larger “business class” UPS units even come with warnings not to install them on their sides.

  2. I like the idea of electric bikes, but as an “all year long” biker, the noise… or the lake of it actually, make it too weird for me.

    I would prefer an hydrogen combustion motor. Make it greener and keep the noise.

    1. Just add a few speakers and you can make it sound like whatever you want it to.
      Hook that up to a circuit board so that it sounds different when you do different things, like rev your motor vs coasting.
      that would be a cool little side project…..
      Little tiny bike GREAT BIG NOISE.

  3. Great and all.

    Seen it too many times however.

    To many faults to be accounted for.

    Lead batteries are not designed with constant draining in mind. They can deliver big on amps, but not for long.

    LiPo is a great substitute. There is however a big problem with these batteries. They can explode.
    Now, ask yourself do you wanna sit on a potential boom-boom?

    Overcharging being one of the main causes. Also shortage can be killer.

    Then there is the weight issue with a lead battery, or a set in this case.

    This is a nice hack, but not a progression.

    Take a look at the big companies.


    80kg/150lbs for example.

      1. The chance of gasoline exploding randomly in a properly designed engine is far less than that of batteries, under unknown changing conditions exploding. Where do you get the idea that a regular gas engine will explode randomly? Also, it’s called an internal COMBUSTION engine for a reason, it burns the fuel, I think the knowledge of the risks of that are apparent to all people.

    1. Those are deep cycle lead acids – they’re designed for long usage, vs a car’s starting battery having the characteristics you describe.

      LiPO are also much more solid batteries than scaremongers (ie, you) like to describe. Don’t mistreat them, they won’t mistreat you.

      [@hackaday fix your silly report comment button]

    2. LiFePo (Lithium Iron Phosphate) batteries are a nice compromise for this. They are safer than LiPo, have a rigid outer container, high quality cells can deep discharge just fine, and still have a higher energy density than lead-acid. Most LiFePo batteries are around the same weight/power ratio as Nickel Metal Hydride cells, but better lifespans.
      I have a simple 48V LiFePo pack on my electric scooter, and it works great.

    1. The only way the gasoline in your tank is going boom is if you mix it with air at slightly less than 14.5:1 air to fuel by weight. You have to get it right within 2 percentage points or it either won’t ignite, or will just give you a little fup and a flame.

      That’s why cars only explode in the movies.

      LiPO batteries on the other hand are like welding torches once they ignite. You don’t want to get them wet, punctured, overcharged, undercharged, short-circuited or too hot. They don’t go boom either, but having a foot long 3000 F flame lick your crotch isn’t exactly what I’d call fun.

  4. I have a Honda PCX 125. It’s mostly popular in Europe and Asia, but man is this a beauty. I regularly get 120mpg and it takes about 2 and a half gallons per fill up. Yes, that means I get 240mpg minimum before having to refuel.

    You wouldn’t catch me swapping out for an electric model simply because the costs are not worth it. At 120mpg I spend very little on fuel, but going electric would mean paying for the electricity (people seem to forget that point!) AND replacing the battery every year or two.

    If I had junk parts to build a bike from scratch, maybe, but whilst bikes like mine exist and electric bikes offer such low range for the costs incurred, electric bikes are not going to take off…

    1. Of course a home-built electric bike is going to be expensive when you’re competing with a mass-produced high efficiency ICE-powered bike. But let’s assume you haven’t already got an expensive new bike but you have got a scrap bike and some other junk, and that makes this a no-brainer.

      Or you could just sit back and watch, knowing that for some people DIY is more important than paying the absolute minimum to get by.

    2. While your bike may be economical, ANY amount of energy produced from petrol, rather than electricity from the mains, is much more expensive per watt. Electric motors are round about 100% efficient so there’s no losses in the system. Point is, an electric bike would cost less to fuel than a petrol one.

      You also meant, of course, 240 miles on a tank, not 240mpg.

      Electric bikes’ main problem is lack of range. Apart from that they’re better in every other way. In progressive countries, you might find that tolls and even taxes are waived, or lowered, for electric vehicles.

  5. @NewCommentor1283- Regarding running these batteries on their side- those are Optima Yellowtops, which aren’t just SLA, they’re AGM- absorbed glass mat. Their internal construction is different from most car batteries, and if I recall correctly, the manufacturer approved sideways installation (but not upside down).

    @Syrus- you’re absolutely right about lead acid batteries, but in the designer’s defense, these are about the best lead based batteries that he could have picked. They are “dual purpose”, able to handle deep discharge cycles far better than most lead based batteries. I’ve used them in competition power wheelchairs, and the only batteries I’ve found that were better were Odyssey PC1500s. The Optima Yellowtops last a long time and outperform the standard gel batteries that come with the chairs, you just need to make sure not to run them too flat, and to charge them at a proper voltage.

    The designer would get the most life out of these by charging in parallel with a high precision three stage charger.

    1. yes i know SLA can be used on its side, and it is SLA that i was indeed talking about, what i meant was the batterys internal design anticipates the battery to be chaged in an “almost-upright” orientation, whereas gel wants totaly upright charging and the starting battery wants always-always upright always.
      those LEAD PLATES weigh a ton!
      and they are attached by……
      that rust in the water……

      i was talking permenent installation where one going bad wouldnt ruin the other / stop u from getting home. aka put a freakin 100A fuse and the prob is nil if they are in parallel.
      he built a fun toy :D which BTW is awesome

      fyi if i do 24 volt its a bank of 4 batts, not 2 hehe

      … but MY sales man told me it would only last 1/5 the time when always charged at a 90 deg. angle ie sideways aka how this bike is setup. he said they would last a season of normal use sideways,,, i think that is the certification your talking about

      but alas, we can both agree it doesnt apply if the batteries are taken out of the bike to charge indoors, after all you paid extra for them to be safe to chage indoors!

      PPS: the bike is harder to steal if the batterys are removed and there is an electricaly (un)locked park-brake :D hehehe

  6. I saw a lot of about 250 broken ps3 controllers for sale on ebay once for about $500. Each one has a 4.2V 1.8Ah lithium ultra low profile battery pack. I bet slapping 250 of those into that bike would make for one hell of a ride.

    1. I wouldn’t think so.
      To make a bank of 48v @1.8aH you’d need:
      48 / 4.2 = 11.4285714 ~11 batteries (46.2v)

      then using them in series/parellel for capacity:
      250 / 11.4285714 = 21.8750001 21 banks of 1.8aH

      This gives you a battery pack supplying 37.8aH@46.2v

      I’m not sure how much of a drain those batteries expect but I can be sure that it’s probably not on this scale.

      1. You are right, by guestimation was pretty far off.
        Production electric street bikes have battery packs that can deliver about 6KWh. The ones I found by “Zero” run at 70V, so they are pushing almost 85Ah. That would be 47 banks of 17 batteries each or approx 800 cells total. There 15g a piece which would weigh in total 26 pounds. Would be interesting trying to find a charger that could handle that properly.

  7. I used to have the same motorcycle years ago and sold it when the motor was on its way out. It was a fun bike, but I can imagine it to be a lot more fun with electricity (should have kept it!). Very cool stuff, I’m glad Ben decided to share the process with everyone.

  8. Needs an amplified speaker playing engine sounds (or other crazy effects) with frequency and volume corresponding to gear and throttle position…

    …loud pipes save lives.

    1. Do you ride a motorcycle? I’m not actually sure that’s true.

      If you had actually read through the instructable you’ll note that at the end he discusses installing an obnoxious noisemaker into the empty gas tank, and links to another instructable where he actually does that.

  9. Most of the sound from loud pipes is directed behind the bike. While in your car, it’s pretty easy to not hear a loud bike passing until it’s almost next to you.
    It’s bad time to distract the person in the car you’re passing, and they’re bound to swerve into your lane when they look around to see what the sound is coming from.

    I’m not saying don’t run loud pipes, just don’t expect it to help since people will still not notice you even if your bike plays ice cream truck music and you drive around while on fire.

    1. More than car drivers; by the time they notice your tailpipes, you’ve already overtaken them. I’d worry about pedestrians. I’d worry more about pedestrians.

      You can’t judge the speed of a vehicle coming towards you very accurately because human stereoscopic vision works only up to 30 feet or so, and the rest of the way you judge distance from other cues. A person who’s used to vehicles that make noise (esp. doppler effect) could step in front of a silent electric bike because from their point of view it’s barely moving at all.

  10. Ah. My quarterly “Something interesting on my least favorite website” event.

    Anyway, I’m glad that someone is also enjoying an converting a motorcycle to electric. Despite the obvious flaws & limitations due to design choices.

    Also a lot of commenters sounds like they have almost no idea what they are talking about, nor have any experience actually undertaking such project, yet feel compelled to express their faux cynicism anyway… pity it just makes them look foolish.

    1. I agree. I never understand why people feel the need tear down someone else’s project. Technical critique is one thing but some of these comments are so immature.

      This is a great build and a great write-up.

  11. Awesome, let’s see more EV conversions of cars and bikes! In little belgium we had to do the oposite and convert an ev bike to ev go-kart because the bike was not allowed on the road ;)

    Regarding the lipo scare tactics here. Explosion is only possible if you use them like an idiot (charging them with a complete wrong circuit or shorting them for a long period: basically not using fuses or a completely wrong charging circuit). Same applies to every gasoline car and bike today: if you crash it or put a cigarette in your tank you’re much more likely to get a huge explosion. Much larger than any lipo will give you ;).

    The videos you see on youtube of a lipo exploding is equivalent to someone putting a match into a gasoline tank. The latter will give you a lot more boom boom and both are equally foolish things to do…

  12. How about some people learning some more about gasoline’s chemical properties for a start, before commenting?

    It needs an open burning flame (Oxide reaction) , not a searing cigarrete.

    Cigarette’s won’t even ignite gas. Mythbusters even tested it.

    LiPo scare tactics and scaremongers.
    People, get a grip. Please.

    Be a bit more open minded and think relative.
    To optimize this design, is to go to a different/alternative power source.
    Meaning a different kind of elemental combination.
    I can understand that this is just a DIY/Hack, but please.

    @Walter. Seen a bit to much movies, have you?

    If you are talking about making something that is sustainable and even properly designed i’d suggest LiPo also. Problem is, it requires more safety features to be implemented to achieve a proper functioning, safe design.

    1. Agreed. A lit cigarette is only smoldering technically. This used to be a party game I would play: Pour some gasoline in a bowl. Light a cigarette. Take bets about how you’re going to be horribly disfigured when you put the cigarette out in the gasoline. Put it out with a smile, collect money from all the people who’ve seen too many Hollywood movies

  13. Hey Guys! That’s MY MOTORCYCLE!

    I geared mine to a top speed of 45mph, because I am almost always in the city in 25MPH zones. It’s just a single drive sprocket, so it would be easy to swap out for a 60-65mph top speed without changing anything else, but why bother?

    The other cycle in the one video belongs to my friend, Tony. He put a lot of time, work, and money into that project, but boy does it show! It has a nearly 100 mph top speed. (That said, mines more comfortable!) Somebody else posted a link to his site earlier.

    I have played with a sound system, using self-powered speakers, and an iPod loaded up with different motorcycle sounds. It actually works really well with unattentive pedestrians in parking lots. That, and I always have my horn as well…

    The batteries are Optima Yellow Tops. They are actually designed to be used in any direction except upside-down. They also put out almost 900 cranking amps, so they give the most oooomf you will get out of any lead-acid battery.

    As another fun feature of my cycle, I have been charging it with a 48V UPS. In case of a blackout, I can run 48VDC power from the cycle, through the uninterruptable power supply (inverted to AC power) and backfeed it to my house. Can anyone else run their household power from their motorcycle?

    Please read the Instructable, there’s tons of info packed in there. It’s also entered in two contests at Instuctables, so please vote for it if you like it! (Contest grand prizes are CNC machines that will let our makerspace build more cooler projects!)

    I also made an instructional DVD, teaching people how they can build their own electric motorcycle.

  14. Fantastic work, Ben, Congratulations!

    The world is full of only two types of people:

    1. People brave enough to create things out of their own ideas, and

    2. Those who criticize and point out what they hope is wrong with other people’s work.

    Congratulations for being in the first category.

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