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Thread: 50cc Scooter conversion

  1. #1
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    50cc Scooter conversion

    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 (1250/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; 2 Weeks Ago at 0547.

  2. #2
    I should be working! furyphoto's Avatar
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    This type of scooter project is totally doable. I would recommend however, if it is to be used by a 14 year old, and if others might copy your work, that you consider a more stable battery chemistry than LiPo.

    For that size scooter, you might consider a hub motor. If you haven't seen already, checkout EV Album to see what others have done. http://www.evalbum.com/type/SCMM

    Here is a thread on Endless Sphere about an appropriate motor for a 50cc scooter https://endless-sphere.com/forums/viewtopic.php?t=81702
    Last edited by furyphoto; 2 Weeks Ago at 2257.


    My ElMoto Project "Electric Hurricane" - 1987 Honda CBR600 F1: Check out my Build ALBUM
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  4. #3
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    welcome here.
    Always great to hear about new projects.

    Sounds doable but as Andrew suggests check out LiFePo4 Batts for motor and aux.bat.
    2kwh should be doable still.
    also i would consider a bigger charger.. 4-5 hrs for 2 Kwh means a 4-500 watts charger... even on 110V (dont know your location) a 0,8-1kw still should not trigger a circuit breaker. With only aprox 20 km range a "relative fast charge" would greatly enhance the usability of the scooter... (school morning and lake/football/friends in afternoon right after homework..) at not too much aditional cost..



  5. #4
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    Hi furyphoto and flo !
    Thanks for the help / encouragement ! Appreciated.
    Bad nomenclature when I said Li-Po. I hadn't really thought about my typing. Should have said Li-ion, in fact the batteries I always use (many, many battery powered projects - just not any ICE conversions until just recenty) are 18650 LiFePo4 cells (Panasonic NCR18650GA). They're 3350mAHr capacity (another learning process and a lot of research re: battery chemistries etc). I'm just finishing off the first of two 20S4P battery packs I've made for the scoot. After I'd 'settled' on the Panasonics, I spent quite some a time working out whether to solder or spot-weld. Deciding spot-welding and fusing was 'best practice', I then spent another week or so designing, building and fine-tuning a suitable spot-welder for them. That was quite a while ago now but, with the use of my 3D printer, I think I've come up with a suitable unit that's now made many a spot-welded battery pack. I'll post up some pics when i get a mo.
    So, apologies for my misleading 'LiPo' post

    Chargers. Another item I've 'struggled' over. If I understand the Panasonic datasheet correctly, I should only charge these things at 0.7C (although I see people charging them with more). Your'er right, flo, I foresee / have built TWO 20S4P packs (simply for size/weight, fitting on the scoot and carrying about). On the scoot the two will be connected in parallel, effectively making a 20S8P pack so I guess;
    4 x 3350 x 0.7 (-ish) mA = 9.38Amps = a 10A charger !
    Yeah ! Now you mention it I'll look at the budget and (ideally) buy 2 chargers, one x 10A unit for individual charging in the house / garage and one x 20A (parallel) on-board charger. That would make charging super quick (x4) whilst remaining within safe territory.
    I think I'd 'settled' on the 5A unit jeuct because of its avalability (eBay / AliExpress) and cost; circa 55Euro ! But, budget withstanding, I'll upgarde that to a 10A unit or maybe both ! I'm keen to be able to remove the batts overnight / for charging away from home for security and concerns over temperature / cold nights.
    My logic is sound ? Or... ? Always open to advice.

    As to where I'm based - Brittany, north west France. Everyone has a scoot / small 50cc (trials-style) 'moto' here !!

    I'll post up some pics later.
    Again, thanks both. Food for thought. I'm off to look at chargers !!

  6. #5
    Senior Member Stevo's Avatar
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    Or make your own charger with Meanwell power supplies.They make many choices with adjust ability. You can wire 2 in series to get the voltage where you need it AND they can be wired in parallel to get more amperage if you need it. I made one using 2 in series to get up to 120 volts... it charges at 10 amps with 220vac. My 75 aHr pack charges in about 3-6 hrs depending on how far down I am. Im going to redo mine to wire in a control circuit that will shut off the charger when the BMS hits high cell.
    Last edited by Stevo; 2 Weeks Ago at 0903.
    Current rides: '96 Honda Ohlins VFR, '03 Cannondale C440R, '03 Cannondale Cannibal, '06 Yamaha 450 Wolverine 4x4
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  7. #6
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    Hi Stevo,
    That sounds like the sort of functionality I was looking for. If possible I'd like a charger that I can 'limit' to cut-off at the 80% full point (or there abouts). I'm probably being retentive but I'm learning and...
    I'll go take a look anyways and see what I come up with. Thanks.

  8. #7
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    An update :
    This is the scoot I purchased for 200Euro. Great nick really except, like I say, it has an intermittent spark issue and the ubiquitous oil leak
    Scooter (Arrival)(250x141px).jpg

    ...and this is it once stripped down :
    !Scoot stripped-SideOn(512x288px).jpg

    This week I plan to finish tidying up the electrics ready for the Li-Ions, Motor and Controller etc...

    I'm still not yet sure how I'm going to 'link' the mid-mount motor to the rear wheel. Th motor I've purchased has a max 5000 rpm which, from calculations, wont be sufficient with the existing vari-drive and internal-to-rear-hub 14:1 gear box but we'll see when I get that far !
    I have stripped down the gearbox and see no way to 'bypass' it. Sure, I can lengthen the gears within it but initial calcs would indicate I can't lengthen them enough.
    I have given a LOT of thought to removing the vari-drive and replacing it with a fixed belt arrangement but fixing the front belt pulley looks really restricted as the motor has a short shaft and a T8F machined head on it...
    I'm now thinking about whether I can remove the var-drive completely and modify the rear-gearbox input shaft to accept a T8F sprocket directly. The challenge here is that it seems pretty impossible for the average DIY'er to remove the input shaft from the gearbox (in order to machine the T8F slotted head and nut thread... So... my little head is still working out the options, challenges, advantages and disadvantages of each here. Like I said at the outset, the idea here is NOT to simply throw money at the project but, rather, to keep the whole project within the remit of an average / competent DIY'er... otherwise I still foresee tons of these things continuing to be scrapped / not tried to be converted due to cost and difficulties etc... Having said all that I'm just as keen to make sure the final project isn't heath-robinson and is still quick enough etc to be worth-while doing ! We'll see...

  9. #8
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    You'll have to enlighten some of us as to what a"T8F sprocket" is. The vari-drive is usually a waste of time and effort with an electric motor drive. Drive ratio wise you'll probably end up with something like this crude set-up:Scooter Drive.jpg
    Don't weld sprockets to shafts like in this example! ebay is full of sprockets(for tooth belt and chain drives) and taper lock bushings to fit a wide variety of shaft diameters( English and metric), so you don't have to permanently attach the sprockets.


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