Generic 50cc Scooter conversion

General Discussion about large electric scooters and motorcycles and other things with no pedals.
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3DRoboGuy   100 µW

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Generic 50cc Scooter conversion

Post by 3DRoboGuy » May 05 2019 5:54am

Hi,
First time on the forum, so introductions first :
my name's Ian.
I'm an electrical/electronic engineer to trade and am reasonably handy.
I now live in France where nearly all the 14+ year-olds ride a 50cc petrol bike / scooter - least-ways my son and all his mates do ! Man, they're noisy, stinky, leaky and almost always needing repaired - the scooters, I mean !

After a bit of googling for some parts one day, I became distracted by emission control regs, scooters being banned from cities or charged for daily access to them... It seems that many thousands of older 'dirty' 50cc petrol scooters are facing premature scrapping (Netherlands / France) due to their age and the fact they are considered 'dirty'.

I'm pretty passionate (in a calm and resigned way, I think) about the planet, weather changes, greenhouse gas / small partical emissions and started to think of how I could make my son's (and his mates') scooters more eco- (and noise) friendly.

Anyways, I need a project and thought I'd convert one to electric.
I already have the scooter : 50cc chinese in good nick but with an annoying oil leak and intermittent spark problem.

My thoughts so far :
a 3Kw mid-mount AC or BLDC motor and compatible controller
a 72V LiPo battery pack - 20S8P (2Kw - can add to this later if required)
a small 12V LiPo battery pack for ignition / start-up etc
a 72/12V converter to charging the 12V LiPo pack and supplying lights and horn etc
a pair of SSR contactor(s) - 1 hi-voltage (72V) and 1 x lo-voltage (12V)

a similar acceleration & top speed (better if poss. but no worse)
20Km+ range / autonomy (with the internal 2Kw pack)
an onboard charger (4 to 5 hour charge period)
provision for an additional 2Kw of LiPo (increase range to around 40Km)

I intend to keep chassis / original equipment mods to a bare minimum - except the switch from ICE to electric and I'd like to think that as many decisions as possible will be based upon maintaining DIY simplicity / transfer to other makes of scooter. I don't really know the implications re: re-licencing / MOT / TuV but believe it to be pretty simple (having spoken to the DVLA) in the UK. In France, it's most impossible (currently) but everyone 'upgrades' their 50cc 'scoots' and no-one blinks an eye. No idea about the Netherlands and further afield.

The 'donor' scooter is to be the 'el-cheapo' Chinese RPS scooter in great nick, the parts could always be sold on - if I can find a buyer.
I'd like to think that 800 - 1000 Euro would do the trick. Considering the current London ULEZ charges (12£50/day) this would equate to a 3 - 4 month (5 days a week) reclaim period... seems pretty reasonable IF it can be done...

I'm thinking of documenting the whole project with a view to enabling others to copy... I'm most deffinitely not a You-Tuber but I could update the forum with progress and even make a website for posterity ;)

Does this sound feasible ? Any ideas / advice / thoughts ?
Last edited by 3DRoboGuy on May 05 2019 7:46am, edited 1 time in total.

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eee291   10 kW

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Re: Generic 50cc Scooter conversion

Post by eee291 » May 05 2019 6:31am

With a 2.2Kwh of battery I can get ~45Km so I don't think you'll need a bigger battery.

Having a 12V Battery is good for redundancy, I just carry a second 72V-12V converter with me in case the current one fails.

Here is a motor I can suggest for the conversion:
http://www.eastgem.net/da90-k1.html
http://www.eastgem.net/accsesories.html
It already has the slotted axle that can take standard sprockets.

3DRoboGuy   100 µW

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Re: Generic 50cc Scooter conversion

Post by 3DRoboGuy » May 05 2019 7:42am

Hi eee291,
Thanks for the message.
That's a great range and indicates circa 50W / Km. My calculations / reasearch had put me at about 100W/Km !
What ride are you running ?
What power motor are you using ?
At what speed do you get the 45Km ?
I ask because I'm really keen to keep the scooter I have 'attractive' in that I'd like it to be *at least* as fast as the original; 45KmH. I need to keep my son and his mates 'interested'... :D

Thanks in advance. I'm off to gen-up on your links !

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eee291   10 kW

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Re: Generic 50cc Scooter conversion

Post by eee291 » May 05 2019 8:10am

It has a 3Kw hub motor with a 5Kw Controller, range was 45Km at ~50km/h. Top speed was about 70Km/h limited to 54 now since my little brother was caught doing 60, ended up paying 240€. 70€ for speeding and 170€ because it was registered on my name. :cry:
From what I read online 40-45Wh/km is pretty standard for a 45Km/h scooter

Currently I'm converting a Derbi Senda SM. It's going real slow right now but specs will be something like 18Kw peak motor, (24S2P) 4.4Kwh Battery and
a 2-3.6Kw charger on board.

3DRoboGuy   100 µW

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Re: Generic 50cc Scooter conversion

Post by 3DRoboGuy » May 05 2019 9:07am

Aha... Brilliant info. Thanks.
Dunno how I calculated the 100W/Km :oops: but it matters not - I prefer your 50W/Km !! :D
We just bought our son (15yrs old) an old Reiju 50cc (very similar to your Derbi) and, when the scoot is completed, that's to be the next candidate (or something similar if he won't let me play with the Reiju) which should benefit from the scoot's learning curve :twisted:

I'll post some pics of my work as I go...
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SlowCo   100 kW

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Re: Generic 50cc Scooter conversion

Post by SlowCo » May 05 2019 11:56am

Always nice to see conversions from ICE to electric.
The biggest problem with an ICE scooter like the one you want to convert is the friction based CVT belt system. It is not wise to only replace the ICE engine and keep the CVT system in place. It is very inefficient and will eat a lot of power. So then the 100Wh/km will be more likely.
That's why factory made electric scooters mostly have a hub motor rear wheel. If you want to use a hub motor rear wheel you'll have to fabricate a swing arm. Or you can use the existing casing and replace the CVT belt system for a fixed gearing using chain and sprockets (or a belt and pulley's). Then you can use a mid motor in place of the ICE engine.

3DRoboGuy   100 µW

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Re: Generic 50cc Scooter conversion

Post by 3DRoboGuy » May 06 2019 5:36am

Hi SlowCo.
Thanks for your message. I'm with you re: the CVT belt drive. I 'm leaning towards a chain / sprocket arrangement and am currently thinking of a 17:11 sprocket set-up; the 17 up front, on the motor, and the 11 back aft.
I think this should allow a 5000rpm mid-mount motor to drive the rear wheel (T8F shaft), through the swing-arm gearbox (14:1 reduction that I can't figure out how to effectively, and not too expensively, remove ! ) at around 57Kph (max). I can always increase the rear / decrease the front pinion(s) to adjust the final acceleration / speed. (17:13 would provide a lower top speed but better acceleration... )
The 'downside' with this, as I currently see it, will be chain/sprocket noise (compared to belt), no clutch / inability to freewheel when pushing the scoot and any soft-start restrictions placed upon me by the motor controller itself. I don't see any of these as 'deal-breakers' - just stuff I'll need to overcome.
You're right too about a hub motor option. I thought about this long and hard but found trying to match a hub motor to the swingarm gearbox o/p shaft and replacing the existing internal rear drum brake with a different set-up to be too invasive and too 'scoot'-specific; I felt each 'scoot' make/model would require specific-to-'scoot' instructions and post-conversion certification may well be harder should the swingarm and rear brake ass'y have been changed too much. The chain/sprocket method seems to negate major structural changes... but I may well yet be wrong (often am ! ) and wish I'd chosen a different path... time will tell...
As I said, the idea for me is to try and keep the whole conversion within the realms of a DIY-er and the cost sub-1000€ so that anyone with a 'dirty' scooter could convert to electric pretty quickly and within a tight budget thereby (from my point of view) making it more attractive.

Anyways, in frustration and wishing to 'get on', I ordered a 3Kw Kunray BLDC motor/controller unit over the weekend. I hope I won't live to regret my inclusiveness!!
I've also started getting things together to build my Li-Po battery packs. Currently looking at a pair of 1Kw packs 20S4P configuration...

I'll post some pics as I go and no doubt will be back asking for help :confused:

Thanks again.

SlowCo   100 kW

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Re: Generic 50cc Scooter conversion

Post by SlowCo » May 06 2019 7:39am

:thumb:
I wish you good luck and enjoy the challenge!

3DRoboGuy   100 µW

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Re: Generic 50cc Scooter conversion

Post by 3DRoboGuy » May 06 2019 9:56am

ee291

I was thinking about your Derbi Senda :mrgreen:
Currently I'm converting a Derbi Senda SM. It's going real slow right now but specs will be something like 18Kw peak motor, (24S2P) 4.4Kwh Battery and
a 2-3.6Kw charger on board.
Please excuse my questions : Super interesed and rather envious; I wish I'd started with a non-scoot although it is (for me) a very interesting project and not too expensive to start-off with.
Is it pretty simple to register a converted bike where you live ?
Do you have a thread I can follow ?
Best of luck and hope your build speeds up for you.

3DRoboGuy   100 µW

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Re: Generic 50cc Scooter conversion

Post by 3DRoboGuy » May 06 2019 9:57am

SlowCo,
Thanks for the encouragement, I'll be back with a load of questions I'm sure.
...and more pics.

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eee291   10 kW

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Re: Generic 50cc Scooter conversion

Post by eee291 » May 06 2019 11:24am

3DRoboGuy wrote:
May 06 2019 9:56am
ee291

I was thinking about your Derbi Senda :mrgreen:
Currently I'm converting a Derbi Senda SM. It's going real slow right now but specs will be something like 18Kw peak motor, (24S2P) 4.4Kwh Battery and
a 2-3.6Kw charger on board.
Please excuse my questions : Super interesed and rather envious; I wish I'd started with a non-scoot although it is (for me) a very interesting project and not too expensive to start-off with.
Is it pretty simple to register a converted bike where you live ?
Do you have a thread I can follow ?
Best of luck and hope your build speeds up for you.
The Derbi is still stock, I just bought Controller,Motor,Battery etc. I could pretty much start right now but I'm still waiting on someone.

The registration won't be hard but it will be expensive! Anywhere from 450€-750€ (depending on how far I'm willing to travel) for the paperwork excluding registration which could be another 180€ if I have to re-register it.
Cost for parts so far were about 1500€ excluding the Derbi.

Apparently it is really cheap in some states here to get a scooter registered. I saw a guy take a Mach1 sitting scooter and registered it as a 50cc equivalent scooter, all he had to do was add some indicators and wear a helmet. Cost him like 80€

3DRoboGuy   100 µW

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Re: Generic 50cc Scooter conversion

Post by 3DRoboGuy » May 07 2019 4:43am

eee291,
Thanks for that.
Like I say, sounds super interesting. Hope you keep us informed of progress - I'll look forward to that.
Good luck.

Bikegirl   1 mW

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Re: Generic 50cc Scooter conversion

Post by Bikegirl » May 07 2019 7:04am

3DRoboGuy wrote:
May 06 2019 5:36am

Anyways, in frustration and wishing to 'get on', I ordered a 3Kw Kunray BLDC motor/controller unit over the weekend. I hope I won't live to regret my inclusiveness!!
I've also started getting things together to build my Li-Po battery packs. Currently looking at a pair of 1Kw packs 20S4P configuration...

I'll post some pics as I go and no doubt will be back asking for help :confused:

Thanks again.
Hi 3DRoboGuy, i'm buying the same motor and controller with 72v 20s1p lipo pack for my drift trike.

Super keen to see how your build goes and wondering what kind of charger you decided on?

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Dui, ni shuo de dui   100 W

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Re: Generic 50cc Scooter conversion

Post by Dui, ni shuo de dui » May 07 2019 9:27pm

3DRoboGuy wrote:
May 05 2019 5:54am
Hi,
First time on the forum, so introductions first :

Does this sound feasible ? Any ideas / advice / thoughts ?
Sounds like a sweet project.
But you said that you are living in France. And as far as I know, regulations are pretty harsh for DIY vehicles there.
I think that might be the biggest difficulty in the build you plan. You really need to dig into that part.

Technically speaking it won't be too hard to build an electric scooter capable of over performing a 50cc. Since you already purchased the bike I think that an inboard motor is probably the easiest solution, unless you can easily install a swingarm for a hub motor in which case go for it, hub motors are awesome for scooters.
If it was my build and given your target range of only 20km, I would probably keep the transmission, or at least I would experiment with it first and then, later, maybe go for a chain instead if it turns out to be problematic. Sure you lose a bit of efficiency, but you gain starting torque and/or max speed so in the end it might be interesting. Efficiency is for people who need a lot of range, doing 20 or 30km is really no problem.

I don't know much about inboard motors so I can't help with the specifics about battery size, controller or motors here, but if I had to guess I'd say that a 3-4000W motor should be plenty enough, but plan for a very good battery and try to fit as many Ah as you can while keeping the voltage at 72V minimum. Regarding autonomy, well it totally depends on riding style but generally speaking for a scooter with a hub motor, my experience is that 1Ah of battery capacity = 1km of distance, if you ride it hard. So in your case, doing 20km might be doable with 20Ah. But then your discharge rate might be too high for your cells so you will probably have to go for 30 or even 40Ah.
Forget about the 12V battery, doesn't really worth the cost, complication, weight, reliability issues... any DC/DC converter will do the job efficiently enough and you generally don't have a lot of stuff to power aside from the front lights. Just buy a good, overpowered one (for example if you need 3 amps, purchase a DCDC converter capable of 6 Amps or more). I did that on all my builds and so far I never blew a single one. And even if the 12V converter fails, you can still ride home and change it later, most good controllers don't need it at all. Keep that precious space for your main battery, you will need to draw a lot of amps from it so it needs to be big.

I'd forget about LiPo, they are harder to maintain, they don't last long and they are delicate. If your scooter is intended for a kid it will have to be tough and withstand a lot of abuse, go for an other chemistry who can provide you with high continuous or burst discharge currents and last longer.

Also, I think that 1000Euro will be short for such a build in France. That would be the price for me in China, but everything is way cheaper here. In my opinion you can easily double that.
:bolt: :bolt: My electric Ninja 250 clone: 16 000W 72V40Ah A123 cells : :bolt: :bolt:
https://endless-sphere.com/forums/viewt ... 12&t=90032

:bolt: :bolt: My electric Scooter: 11 000W 72V 50Ah LiFePO4 cells: :bolt: :bolt:
https://endless-sphere.com/forums/viewt ... 12&t=75912

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Dui, ni shuo de dui   100 W

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Re: Generic 50cc Scooter conversion

Post by Dui, ni shuo de dui » May 07 2019 9:34pm

3DRoboGuy wrote:
May 06 2019 5:36am
Anyways, in frustration and wishing to 'get on', I ordered a 3Kw Kunray BLDC motor/controller unit over the weekend. I hope I won't live to regret my inclusiveness!!
That seems way underpowered to me!
50A controllers is barely what they put here on lightweight granny scooters.
:bolt: :bolt: My electric Ninja 250 clone: 16 000W 72V40Ah A123 cells : :bolt: :bolt:
https://endless-sphere.com/forums/viewt ... 12&t=90032

:bolt: :bolt: My electric Scooter: 11 000W 72V 50Ah LiFePO4 cells: :bolt: :bolt:
https://endless-sphere.com/forums/viewt ... 12&t=75912

3DRoboGuy   100 µW

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Re: Generic 50cc Scooter conversion

Post by 3DRoboGuy » May 16 2019 12:14pm

Hi Bikegirl,
Thanks. Sounds even more interesting too !
Here's where I am at the moment; stripped down and ready for some electric kit !

<EDIT>
I forgot : I decided (just before the last post :oops: ) to go for a 5A unit - simply because I was trying to keep costs down !
To be fair, a 10A would be the max for my chosen battery type / pack size and is now on order too (I am making my batteries so have a little cash to spare).

I'll let you know how I get on with the 5A version - it arrived this week - and I'm pretty much finished with my battery building so will try it out later this coming week. :)
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3DRoboGuy   100 µW

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Re: Generic 50cc Scooter conversion

Post by 3DRoboGuy » May 16 2019 12:25pm

Hi Dui, ni shuo de dui,
Unfortunately the max power allowed in France is 3Kw / 4.5Hp and I am trying to keep the scoot as close to original / 'in spec' as possible for minimum re-approval hassle. Additionally... it is only for a 15 - 16 year old so 50Kmh would be acceptable, 60Kmh would be (for legality) WAY over the top but, from my calculations, should be possible.
Originally, I was looking at a 5Kw unit but, the same sort of calculations, seemed to indicate I'd need a bigger battery pack = more space...

In the end I decided to remain boring... 3Kw... 72V 2Kw battery pack :)

Technical re-licencing (homologation) issues in France ARE really impossible but, like I say, most kids / families modify their kit anyways... So I'm not going to 'bother too much about this. This is, though, one of the reasons I'm trying to keep the spec as close to original as possible.

I'll let you know how I get on with it...

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