[GreatScott] Tests His DIY Battery Pack On His E-Bike

Testing DIY battery pack on E-bike

[GreatScott] has now joined the ranks of Electric Bike users. Or has he? We previously covered how he made his own lithium-ion battery pack to see if doing so would be cheaper than buying a commercially made one. But while it powered his E-bike conversion kit on his benchtop, turning the motor while the wheel was mounted in a vice, that’s no substitution for a real-world test with him on a bike on the road.

Since then he’s designed and 3D printed an enclosure for his DIY battery pack and mounted it on his bike along with most of the rest of his E-bike kit. He couldn’t use the kit’s brake levers since his existing brake levers and gear-shift system share an enclosure. There also weren’t enough instructions in the kit for him to mount the pedal assistance system. But he had enough to do some road testing.

Based on a GPS tracker app on his phone, his top speed was 43 km/h (27 miles per hour). His DIY 5 Ah battery pack was half full after 5 km (3.1 miles) and he was able to ride 11.75 km (7.3 miles) on a single charge. So, success! The battery pack did the job and if he needs to go further then he can build a bigger pack with some idea of how it would improve his travel distance.

Sadly though, he had to remove it all from his bike since he lives in Germany and European rules state that for it to be considered an electric bike, it must be pedal assisted and the speed must the be progressively reduced as it reaches a cut-off speed of 25 km/h (15 miles per hour). In other words, his E-bike was more like a moped or small motorcycle. But it did offer him some good opportunities for hacking, and that’s often enough. Check out his final assembly and testing in the video below.

And there is plenty of room for hacking with E-bikes. This one, for example, forgoes the kit route and is done from scratch and includes a dashboard.

19 thoughts on “[GreatScott] Tests His DIY Battery Pack On His E-Bike

  1. i don’t understand why he choose to remove the entire system instead of attempting to implement the pedal assist and a governor of some sort to abide by the speed limitation.

  2. Not quite. It’s the German laws and regulations. The e-bike rule implementations differ slightly between EU countries, but generally, you can have a bike with a throttle. It’s still limited to 25km/h (above it turns into a moped/motorbike with much stricter regulations). The Vehicle class for this is “L1e-A”. Usually, those also have pedal assist. Power is limited to 1kW as opposed to the 250W of the simple e-bike class.
    Here in Finland they only require a liability insurance, no type approval, no register plate. Nice and simple.
    In Germany it’s more involved, you need insurance, type approval and it might also come with the need for a plate (not sure on the last one). You can get one-off exemptions from type approval, but the handling of this differs on county level!

    1. There is one way to (ab)use a grey area – mountain e-bikes…Once off-road, very few power limits apply ;-)
      Obviously in order to stay legal on-road, you have to limit power, but that can be done by tweaking the firmware of the controller and adding a switch of some kind.

    2. California has similar limits, but enforcement is non-existent beyond manufacturing. So, when I built my first e-bike, I made it so that my two battery packs could be legal (put them in parallel) or fun (put them in series). I can get 55 kph out of mine for 10 minutes in top gear with me producing probably 250 watts (I could hold 290 or so for an hour back when I was racing TTs), and the motor providing the rest. Nobody seems to care that I’m going that fast, cops don’t even look at me.

  3. Indeed, the rules don’t say it has to be certified in any way. Also, there is another category that allows electric power without pedaling and up to 45km/h, called speed pedelecs, but then you need to have insurance and wear a helmet.

  4. Wow. Glad I’m not in the EU. Those rules limit powered bikes to slower speeds than I often pedal my manual bike! I wonder what the rules there are regarding that.

    1. Here in Ottawa, the speed limit for manually pedalled bikes on the pathways is 20 km/h. I do 40 km loops in 2 hours so I guess I pedal within the limits, on average at least.

    2. If you ride your nonelectric bike on the road, you are bound to the speedlimits for that road. Normal limits are 50km/h in villages, but there are a lot of roads that have 40, 30 or even lower speed limits on side roads, residential districts, around schools…

  5. Just FYI for anyone thinking of assembling their own battery..

    I bought two 10AH 6S (44.4V) lipo packs from HobbyKing 2 years ago and they’re still running strong on my 1kW ebike.

    Component cost was the same $140 as GreatScott’s, but no labor, twice the capacity, 2x to 5x the discharge rating, and are physically about 20% smaller.

  6. Can we get the names of these vehicles correct now? At least in Europe we agreed to call the electric bikes where motor support is limited to 25km/h “pedelecs”.
    The next class that allows the motor to assist the rider up to 45km/h are called “e-bikes” and the ones that can accelerate up to 45km/h or faster without riders pedaling assistance are basically electric motorcycles or electric scooters.

  7. Why are you people in Europe scared of breaking the “ebike rules”? Are there e-bike police patrolling all the time? It must be a culture thing. Never J-walk, never walk/cross against the light if there’s no traffic present. Oh think of the example your setting for the children! Come to U.S. and do what you want with your e-bikes, nobody cares. (except NYC).
    It’s like they have prisons for those who break minor laws there.

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