Electric Motorcycle (50cc Equivalant)

Boulter EV

10 mW
Joined
Jan 6, 2017
Messages
31
Hello Everybody. After years of looking at ES forums, I thought it was high time I actually started to write my own things.

I'd like to share with you my project. Its something that is actually nearing completion, but I will upload photos and updates over the next few months.

My own project is really close to many of your projects that I've seen over the years. Its a combination of motorcycle sized propulsion systems with a bicycle inspired frame and components to keep the weight down.

Here is a summary:

Weight: ~40kg
Top Speed: 30mph (limited so it fits in 50cc class)
Motor: LMC LEM-130 95S
Battery: 2.5kwh usable (90% DOD)
Cells: LG 18650 HG2
Pack Configuration: 14S 19P
Battery Pack Design and Construction: Proprietary
Controller: Sigmadrive PMT425S
BMS: Potenza (proprietary)
Bus: Low Speed CAN
Frame/Swing Arm/Rear Hub/Seat etc: Proprietary
Other features: Single Action Removable Battery Pack.
Battery Pack Weight (inc. BMS, Contactor etc): 16kg

As I said above, the project is nearing completion. It has VOSA MSVA and is registered.

I will attach a CAD model screen grab and over the next few weeks I can take you through all of my battery development and the challenges I have wrestled with in case they are of use/interest to anyone, after all, much of my fundamental learning has come from here!
 

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Not too bad really, it took two attempts because there were a few tests that were hard to visualise from reading the paperwork. For example they brush the bike against what looks like a punch bag (I assume this represents a person) and anything that touches it has to have a certain radius. Some other difficulties were things like brake levers. I use down hill mountain bike brakes, but the levers need to have a ball of a certain diameter on the end. I ended up using actual moped brake levers for the first bike which look and feel bad, but for the next bike I'm going adapt the nice hope brake levers I have to match the brakes. You also have to have a certificate of manufacture from the company that built the bike. So I set up a company and wrote a certificate addressed to me, from me!
Components like tyres and lights must be e-marked. Took me ages to find bicycle tyres that are road rated but found some (Schwalbe Crazy Bob).
Insuring it was easy, I've owned a Zero motorcycle and used the same insurer through a broker called Lexham.

Let me know if you want any specific advice
 
Nice,any photos ? Are you going to use chemical metal /jb weld or something like metal putty to make your new levers ?

Sent from my D101 using Tapatalk
 
Thanks, that's really interesting. I've been thinking about doing an electric motorcycle project, and have read through the MSVA handbook. It's all a bit daunting though...

(Bizarrely) brake levers seem one of the trickiest things: downhill mountain bike brakes seem ideal for this sort of low weight vehicle, but the levers generally do not seem to meet the MSVA requirements. (From memory, isn't there also some requirement around access to the hydraulic fluid reservoir - I may have got that wrong though?) I've gone round and round in circles trying out work out whether it is possible to use moped/motorcycle levers with MTB calipers - seems hard to find the right master cylinder piston diameter though (and hoses that fit both ends).

I'm starting to think the easiest option might be motorcycle levers and calipers, but that potentially pushes you towards motorcycle suspension forks, with the resulting weight penalty. It's funny how something as simple of requirements for brake levers can drive a whole range of other design choices. I suppose that's part of the fun of building (or in my case thinking about building) something that hasn't been done much before.

Anyway, thanks for your reply. Looking forward to seeing pics and more info if/when you post...
 
Here's a picture of one of my bikes nearing completion.
 

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Here's some pics of the battery going together

This is half a pack
 

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Maybe not ideal, but if you find any cable-operated brake levers that feel like you want and meet the right specs, you could use those to pull the actual non-spec-meeting hydro levers, mounted inside the frame or somewhere away from the bars.
 
Hi, good idea about the brakes, however I've machined a union so I can hydraulically connect the different levers and brakes. It works ok but the feel is not as good. I'm also using a hydraulic brake light switch.

For the other question about the batteries, the bottom busbars are copper, 0.3mm water jet cut. The top busbars are 1mm bar with 0.3mm tabs. These are photo chemical etched to get the different thickness. I use this company www.ace-uk.net The plastic parts are made from Nylon SLS. All of this is my own design.

Thanks!
 
Are you in the UK? These cell holders are brilliant. Many people have been talking about something similar, but you have actually done it. This is very well done, you could easily get well-paid work as a design consultant.

I am in the USA, and there are 3D print services, plus water-jetted and laser-cut...all I might need is a good design.
 
Hi, I am in the UK yes. Thanks for your comments. I actually work for an automotive OEM and also do a bit of design consultancy on the side.

I need to do some more testing on these parts, and after that the plan is to buy some injection moulding tools to get the piece cost down. I will make them available to anyone that wishes to purchase. We're currently perfecting the weld process, the etching process has altered the surface finish and the welding procedure requires some changes.

I will keep you posted on that.
 
I've seen some moped-sized frames that had a stock space in the center of the frame that easily accepted a squarish battery pack. However, the issue with bicycle frames that are not custom-built is that we have to create a battery that is fairly compact. A shape that is somewhat triangular (or a flat-topped pyramid?) is much more "fittable" to a variety of frames than the beginner rectangle shape. Parallel modules are definitely the format to use.

It would only take a few shapes of 5P paralleled modules to make a system that can be assembled into a variety of pack shapes. Once established, you could expand that into 4P and 6P of the same design. If you only make the parts kit for the buyer to assemble, that insulates you a little against frivolous lawsuits, since the builder is accountable for properly assembling the parts. If you have 99 happy customers with functioning battery packs, then the design is not responsible for the odd 1% who have an issue.

I don't have the time or energy to create my own version, but I can help you by promoting this (at no cost) if you are willing?
 
I thought 'Aussie rules' (sorry!) about mopeds were pretty similar to Europe?

Stealth electric bikes have been doing this game for a while in Oz but I've always wondered why they never made them road legal?
 
Boulter EV said:
Hi, I am in the UK yes. Thanks for your comments. I actually work for an automotive OEM and also do a bit of design consultancy on the side.

I need to do some more testing on these parts, and after that the plan is to buy some injection moulding tools to get the piece cost down. I will make them available to anyone that wishes to purchase. We're currently perfecting the weld process, the etching process has altered the surface finish and the welding procedure requires some changes.

I will keep you posted on that.

I really like your design, compact and sturdy. Very well thought out and not overly complicated. Any plans on doing the same with the new 21700 cells coming from Tesla? Since you are in the automotive business, maybe you are able to source those cells?
 
Hi, thanks for the comments. I've started to look at 21700's. LG are also going to make them, they won't be exclusive to Tesla and Panasonic. However there aren't any significant energy density increases yet, by our measure the biggest driver for moving to 21700 is cost, which is why it'll appear on the model 3 first.

In my view, sticking with 18650 for now is wise. The prices will drop as things start to move to 21700, and there will be more choice for different applications. For example I haven't seen any high discharge cells on the horizon like HG2 or VTC6.

I'm sure they will come and I'm keen to see thermal properties compared to 18650 as I reckon they could be better. Changed my design to suit would be easy enough.

In the meantime I need to work out how to reply to people's specific questions on here by bringing in the question into my reply, how do I do that? Thanks!
 
Nice Packs, When the time comes I want to convert my Honda insight mk1 to have a lithium 18650 pack to replace the nimh. Leaf cells are a good drop in but this pack here also offer more options. Individual cell fusing is a nice touch. It looks like this can be made up but the individual with a spot welder with not too many dramas. Thanks for sharing your progress. Also where abouts in the UK are you based. I'm up in Manchester.
 
Thanks, converting your insight to lithium would be a good project!

I'm in the midlands near Coventry.

We use pulsed arc welding on the tabs rather than resistance welding which is how most spot welders work. This is much better for dissimilar metals.
 
Ok thought it was possibly something different being that you are using copper.

Yeah there is an American chap who is working on a kit to override a lot of the internal circuitry on the insight by reverse engineering it. He will eventually be selling these when he has got a production ready version. He already has some good youtube footage showing his prototype getting 150mpg consistently using leaf cells and a video of how to install a leaf pack in the same place as the original nimh pack. I think I will try to go this way eventually. Mudder on the InsightCentral forums is his name. Linsight is the product.
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Anyway I will stop putting your thread off track now.
 
Boulter EV said:
In the meantime I need to work out how to reply to people's specific questions on here by bringing in the question into my reply, how do I do that? Thanks!

In the upper right corner of everyone's posts there is a button saying ''quote''. Click on it and that post will appear in your reply so you just type your text underneath it. You can keep a portion of the quote by selecting and deleting what you want out of it, making sure you don't delete anything between the two ''[]'' at the beginning and at the end of the quote.

I hope you are right in saying that the price of 18650 will come down. I have been reading that the price of them will come down for the last eight years. :D
 
mistercrash said:
Boulter EV said:
In the meantime I need to work out how to reply to people's specific questions on here by bringing in the question into my reply, how do I do that? Thanks!

In the upper right corner of everyone's posts there is a button saying ''quote''. Click on it and that post will appear in your reply so you just type your text underneath it. You can keep a portion of the quote by selecting and deleting what you want out of it, making sure you don't delete anything between the two ''[]'' at the beginning and at the end of the quote.

I hope you are right in saying that the price of 18650 will come down. I have been reading that the price of them will come down for the last eight years. :D

Thanks for the tip!
 
The reason I was asking about 21700 cells is because of what I read on the net about them. Still don't know if it's true but those cells are between 5750 and 6000mah. But even if it's not true and they just have 5000mah, that would still be a drop in volume of around 20% for the same amount of energy. More like 25% if the cells really are 5.75 to 6ah. I don't see how and why 18650 cells would survive for many years to come. But what do I know. Like you said, it doesn't really matter because your design is easily adaptable to any kind of cylindrical cell that may come in the future, which is part of why it is awesome.
 
mistercrash said:
The reason I was asking about 21700 cells is because of what I read on the net about them. Still don't know if it's true but those cells are between 5750 and 6000mah. But even if it's not true and they just have 5000mah, that would still be a drop in volume of around 20% for the same amount of energy. More like 25% if the cells really are 5.75 to 6ah. I don't see how and why 18650 cells would survive for many years to come. But what do I know. Like you said, it doesn't really matter because your design is easily adaptable to any kind of cylindrical cell that may come in the future, which is part of why it is awesome.

We're seeing at least 5ah already on 21700 so you're right, it's only a matter of time before they supersede 18650. They are slightly less space efficient than 18650's which is worth baring in mind.

At work we've tried to calculate what the optimum size is for a cylindrical cell. Have you ever wondered why 21700? Not 21800, or 22650? We wondered this until done someone from Panasonic told us it's because they could adapt their 18650 machines to 21700 without too much bother, any more than that and they had to replace them entirely.

If you think about it, the best dimension if you only consider geometry for energy density is long but with a small diameter. For cooling large diameter and low height. For strength maybe equal height and diameter. So what's the perfect size?
 
Boulter EV said:
If you think about it, the best dimension if you only consider geometry for energy density is long but with a small diameter. For cooling large diameter and low height. For strength maybe equal height and diameter. So what's the perfect size?

I guess the application dictates the size and so we should have a few sizes to choose from for a while longer.
 
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