Advice on e-conversion for a kid's kart

[feefee23]

Hi all
Following good advice on this forum, i've finished a kids eBike conversion using a hub kit. All happy!
Now onto the next project:
I've got one of these tanks (40kg!): https://www.dino-cars.de/shop/en/gokarts/classics/427/sport-af-red
I'd like to convert to pedal-assist powered as it's a huge wagon and heavy, but with pneumatic tyres i think it'll be great fun in the woods and in fields etc for my 10 year old.

Stupid question maybe, but are there motor controllers that don't need a throttle, and just rely 100% on the pedaling of the user, using a sensor to determine pedalling speed? I dont want to fit an accelerator foot pedal as the user's feet will be on the rotating pedals.
For braking, i will add a disc brake, but any suggestions on how to activate it without adding a brake foot lever (same reason as above, feet will be on the pedals). I guess maybe modify the hand brake lever to be connected to the disc could work? I think that a backpedal motion sensor would be too complicated.

For the motor i'm thinking maybe something like this, connected to the axel with a gear wheel that's separate from the pedal drivetrain: https://www.ebay.co.uk/itm/274269121076
Is 350w enough for a 10 year old, 40kg kart and going up hills?

All advice welcome!

 

[sjpt]

Most motor controllers don't need a throttle (many won't be able to use one). The cadence sensor doesn't generally sense pedal speed (despite its name), just whether or not the pedals are being turned.

Can't see enough of the current brake lever to see how easily it could be adapted.

 

[Nealh]

Those dc motors are brushed motors two phase nearly all the brushed controllers only have throttle control, for pedal/cadence control a brushed controller with pas input will be required . They aren't common now as ebikes now all use brushless three phase.

 

[feefee23]

Those dc motors are brushed motors two phase and usually only work on throttle control, for pedal/cadence control a brushed controller with pas input will be required . They aren't common now as ebikes now all use brushless three phase.

Ahh yes, of course! Thanks Nealh, you were very helpful on my eBike thread too!
I'll need to have a think about this... the two phase geared motors look great as you're getting approx 200RPM output which is very close to what i need on the axel, so no need for huge gear at the back. But it won't allow PAS.
My other option was a mid-drive geared unit (3 phase with PAS), can you recommend anywhere to look for one that wont break the bank, but gives me ~500w ? There are few on ebay but all seem to be either crazy expensive or shipping from China and i dont fancy waiting 6 weeks. With a mid-drive unit i might be able to mount it where the existing pedal crank is, i could even cut up an old scrap bike to get a bottom bracket and weld/bolt that to the kart?

 

[feefee23]

Brushed motor controller with PAS input (pedal assist) the lcd has to be connected to work, throttle doesn't have to be connected.

GREENTIME 36V 48V 350W 18A Brushless DC Motor Controller Ebike Controller +SW900 Display One Set - AliExpress 18

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

Thansk, but that's for a brushless? It says "This controller only works with sensored brushless DC motor "

 

[Nealh]

Thansk, but that's for a brushless? It says "This controller only works with sensored brushless DC motor "

Beg pardon you were too quick, I deleted my post after realising I posted the wrong info. As I mentioned most are throttle only, it might be hard finding pedal assist model.

 

[Nealh]

I got it right this time found one 36v 250w, 17/19a rated any three wire PAS will work.

GREENTIME 36V 48V 350W 18A Brushless DC Motor Controller Ebike Controller +SW900 Display One Set - AliExpress 18

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

 

[feefee23]

I got it right this time found one 36v 250w, 17/19a rated any three wire PAS will work.

GREENTIME 36V 48V 350W 18A Brushless DC Motor Controller Ebike Controller +SW900 Display One Set - AliExpress 18

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

Sorry Nealh i got a bit confused, this link is for a brushless controller right? You're not suggesting this could be used for brushed?

Out of curiosity, on the brushed motors such as this one on eBay, what are all the wires on the controller for? Sadly the eBay posting is not good (i will, of course, ask the seller) but wondered if you can hazard a guess? Could this have PAS on it? I found a similar product and it had connections for motor, battery, charger, isolation switch, lights, brake lights, indicators and throttle, but no PAS :-(

36V DC Electric Motor Speed Controller Throttle 800W Scooter Go-kart E Bike | eBay

Find many great new & used options and get the best deals for 36V DC Electric Motor Speed Controller Throttle 800W Scooter Go-kart E Bike at the best online prices at eBay! Free delivery for many products!

www.ebay.co.uk

 

[Nealh]

Sorry Nealh i got a bit confused, this link is for a brushless controller right? You're not suggesting this could be used for brushed?

For some reason my cut and paste repasted the wrong controller again, I will find the 17/19a brushed controller with PAS input.

 

[Nealh]

Right here goes third time lucky.

Electric Brushed Motor DC Controller 24V 36V 250W Speed Controller with PAS Sensor Port For Electric Bicycle Scooter Accessories - AliExpress 18

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

 

[Nealh]

Out of curiosity, on the brushed motors such as this one on eBay, what are all the wires on the controller for? Sadly the eBay posting is not good (i will, of course, ask the seller) but wondered if you can hazard a guess? Could this have PAS on it? I found a similar product and it had connections for motor, battery, charger, isolation switch, lights, brake lights, indicators and throttle, but no PAS :-(

36V DC Electric Motor Speed Controller Throttle 800W Scooter Go-kart E Bike | eBay

Find many great new & used options and get the best deals for 36V DC Electric Motor Speed Controller Throttle 800W Scooter Go-kart E Bike at the best online prices at eBay! Free delivery for many products!

www.ebay.co.uk

It is twist throttle application only.
Wiring is a pair of battery wires.
A pair of phase wires.
One three wire throttle connector.
Two x two wire brake cut out .
A lock on/off switch.
Battery charge indicator ?
A tail lamp connector ?


Any how you need some battery for that kit it needs 30a min discharge and ideally nearer 40a or more.

 

[feefee23]

Right here goes third time lucky.

Electric Brushed Motor DC Controller 24V 36V 250W Speed Controller with PAS Sensor Port For Electric Bicycle Scooter Accessories - AliExpress 18

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

Ahhh! Fab, that looks good. Do you think the PAS is gradual/proportional? Or just on or off?

 

[Nealh]

The controller is a speed controller so it will give max power/current all the time, the speed input is likely a bit jerky though actual speed is down to how fast the cranks turn. The more magnets the disc has the smoother the pickup will be so opt for 10 or 12 pole disc sensor.

 

[feefee23]

Hey @Nealh, I think i'm going to go with this motor as brushless will give me better PAS control and display etc. What do you think? At 600 RPM i only need to drop the ratio down by a factor of 3 or so to get 200 rpm on the axel which is about what i want. Will getting a PAS and display LCD to work with that controller be quite easy? I would ask the vendor but they're so useless at replying!

I've had a look around at 48v batteries and there aren't that many options for European delivery (not keen to wait for a china shipment). Would you have a recommendation for a good option on 10-13ah unit? Looks like i'm in for £200-250 for this, urgh! Do you think i need to worry about the quality/brand of cells? I've read some people (Greencell) bragging about that they use Panasonic, but are the cheaper unbranded batteries ok?

 

[Nealh]

That controller has PAS and throttle, from what I can see you can't fit a display to it.

Also it has a 30a current rating you won't get a lion battery with a 30a continuous discharge rating for £250.

 

[feefee23]

That controller has PAS and throttle, from what I can see you can't fit a display to it.

Also it has a 30a current rating you won't get a lion battery with a 30a continuous discharge rating for £250.

thanks for reply.
That motor says "Rated current: 13A", did i miss something else?
I'm looking at batteries rated to 25A which would be 1200w peak, so wouldnt that be ok for this 500w motor?

 

[Nealh]

The controller in the link with the motor you supplied says 30a, so it will draw it.
The motor I expect mentions a nominal current and will likely take more.

 

[Benjahmin]

thanks for reply.
That motor says "Rated current: 13A", did i miss something else?
I'm looking at batteries rated to 25A which would be 1200w peak, so wouldnt that be ok for this 500w motor?

The 13A rating is merely the continuous rating of the motor, so 36v*13A=468w. The continuous rating is not what the motor takes but what it can run continuously at without overheating.
As Neal pointed out your controller is rated 30Amax, this is what it will attempt to deliver to the motor on maximum setting. Ideally your battery would have a maximum current rating of 1.5 times that of the controller in order to avoid cell damage and voltage sag.

 

[feefee23]

Ahhh gotcha, I can see in the image of the controller what you are saying now!
okay, I don’t know much about brushless motors and their controllers, do you think I will be able to connect a lower rating controller to this same motor and achieve what I need? I presume I just need to find a controller limited appropriately, which supports PAS and throttle. I would have gone for a lower powered motor but I can’t find any with the right gearing. And I don’t want to spend £££ on a battery with higher discharge. After all my son will be fine with lower acceleration.
Thanks for the help guys!!
Julian

 

[feefee23]

It is twist throttle application only.
Wiring is a pair of battery wires.
A pair of phase wires.
One three wire throttle connector.
Two x two wire brake cut out .
A lock on/off switch.
Battery charge indicator ?
A tail lamp connector ?


Any how you need some battery for that kit it needs 30a min discharge and ideally nearer 40a or more.

Hey @Nealh just picking back on this after a break.
I’m keen for a 48v lion pack, around 10-15aH which would serve the kart and next eBike too. I’ll get a controller with max peak current of 20A, so I was wondering where you’d recommend I look for a battery to go with that? You mentioned I might need a higher battery budget which is ok. Thanks so much for help.