# How fast should my scooter go?



## Mjolinor (Sep 15, 2008)

Buzzing about is fun and I use this thing a lot for going to the shops and stuff, I never go out of town and the main reason for this is that it does not go fast enough.

When I set off the scooter accelerates fine, on a par with everything else away from traffic lights and out of junctions but very quickly it reaches 45 kph and stays there. It doesn't go faster on a slight downhill or slower on a slight uphill. To me it feels to be artificially held back by the controller rather than running out of steam.

The motor is a "DC brushless" though to me it looks like a 3 phase AC motor  with 1750 watts (at 440 RPM, 10 inch wheels), 48 volt 38 Ah battery pack.

Can anyone with a "gut feel" for speeds comment on this, is it a reasonable top speed given the power available, if not is it possible to be fixed with something that is accessible if I rip the controller in bits again. I only need maybe another 5 kph or so to fit into the traffic on the local roads, sick of driving in the gutter.


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## madderscience (Jun 28, 2008)

you don't state what type of scooter it is, but frequently these things have a governed top speed to meet some kind of government mandated limit for the type of vehicle they are. For example, NEV-class vehicles in the United states are limited to 25mph in most states, and electric assist bicycles are limited to 20mph or 1KW of power.

I'd ask the manufacturer if there is a governed top speed, and if there is, if it can be adjusted.

Good Luck


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## Mjolinor (Sep 15, 2008)

In theory the manufacturer is a good option but having asked them lots of things the only reply I get is "buy this, it good price" along with a plethora of pictures, they have not answered the most basic of questions at all.


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## dtbaker (Jan 5, 2008)

I'm not an electronics guy, but the next logical question seems to be HOW these things would typically be speed limited, and if it possible/safe to 'adjust' them yourself. Is there a voltage limiter, or something hardwired in a controller, or adjustable for different markets, etc?

d


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## Mjolinor (Sep 15, 2008)

The electronics side of it I can handle. The information I need though is whether it is worth the effort. The motor produces max power of 1.75 kW at 440 RPM, that is around 33 kph (20 MPH) as it has 10 inch wheels. It weighs 100kg (220lb) and I weigh 90 kg (200lb).

http://www.chinaxingyu.com/XY-EB-023.htm

It is that scooter.

I need to know if 45 kph (28 MPH) is reasonable for that power motor, power source etc. If more could be expected then I will go and look for it but knowing it should be more makes that job a whole lot easier.

I did find an unplugged lead which I plugged in and it did a wonderful job of fixing the top speed to 30 kph, not quite what I was hoping for but close


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## madderscience (Jun 28, 2008)

The 1.75KW (a little over 2HP) rating is really limited by the controller, not the motor. The motor can probably take more current (at least intermittently) and thus put out more horsepower but if that was all the scooter was built to do, you may not be able to sustain higher speeds. Any one (or all four) of the battery current rating, battery voltage, motor, and controller may be a limiting factor in making the scooter go faster.

The website you gave lists the top speed of the scooter at between 45 and 60km/h so I imagine it is capable of faster than what you are getting.

It has a brushless DC motor, so you may have difficulty finding a bigger controller (to allow more current at the same voltage, and thus more power) I'd guess this is probably what you need to be looking at. Do some research on the motor and controller and see what other controllers might be compatible with your motor.

Not a simple answer, sorry.

Good Luck.


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## TX_Dj (Jul 25, 2008)

I'd think it should be able to go faster, but if you re-gear it you'll end up sucking more amps and accelerating slower (and slowing down up hill) and if you re-work the controller you may end up overheating the motor.

My scooter weighs in between 60-70 lbs, is 36v 30A 1000W motor, and with the gearing that gets me ~22 MPH it will be a slug up hills and suck lots of amps trying to do it with the battery ammeter pegged on 30A. If I put the gearing on that gets me ~ 15 MPH it will not slow down most hills, accelerates quickly, pegs to 30A just briefly and tapers off around 10-15 A depending on grade...

Yours should have more power, and may be an artificial limit. Do you have an ammeter you could put on the motor to see what it's getting? or on the battery to see what it's supplying? That'd probably give you a good starting point to figure out what might be possible.


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## Mjolinor (Sep 15, 2008)

Good replies, thanks. That is the information I am after.

I forgot to consider that the batteries may not supply the current required, I am used to lead acid giving all that you ask for in starter type batteries. The batteries in this are Greensaver Silicone and information about them is hard to find.

The controller is made by these people
http://ykjipin.cn.alibaba.com/athena/offerlist/ykjipin-sale-false.html
it is the one priced at 5888 RMB or 1888 RMB, I suspect the latter because when I pull it to bits the PCB is not fully populated with MosFETs. The MosFETs are IRFP2907, it has 6 so the current should not be physically limited by the controller.

I think that an ammeter is the next step which is not too straightforward, being a scooter everything is covered up and really hard to get at, particularly when it's being driven, need a rolling road which wouldn't be a problem if I were in the UK but here in Greece I have few facilities.


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## JohninCR (May 6, 2008)

Current isn't the issue, because current determines torque and the fact that you're not slowing down going uphill means you have sufficient torque. Voltage is what determines speed. If there's an artificial speed governor, that's the easiest fix. A way around it would probably be a larger profile rear tire assuming there's sufficient space in the wheel well. Also, it appears from the link that you have a 48V controller, but you're only running 36v (41v at full charge), so adding another 12v battery in series should give you about 30% more top end speed (assuming no artificial speed limiting governor), though you'll have to watch the low voltage to not over discharge your batteries. 

A final option would be a higher voltage controller. Brushless motors don't have the same voltage limitations of brushed motors. eg On my ebike, I run a 36V 500W hub motor at 84V, so on the hills when it draws 30A, I'm pumping about 2.5kw through the motor. The only issue is excess heat to I do need to be careful not to overheat the motor on hills and prolonged running at wide open throttle.

John


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## Mjolinor (Sep 15, 2008)

It is 48 volt already, fully charged it is a whisker under 52 volts. I don't see anything in the controller that will stop me using more than that, certainly the power circuit will stand more, the problem with that is there is no room to stick another battery, I can't even see the batteries it does have without major dismantling.

I do think, now that I have these answers and thought some more, that the limitation is artificial, in the firmware, to prove that I would need technical data on the batteries, this I can't find.

Ammeter first then working out the limitation circuits in the controller, it definitely has some but they seem to be analogue circuits though they also look pretty trivial, seemingly just a fixed resistor chain that I can change (decrease resistance) to reduce the top speed.

I will also try the maker of the controller to see if they will give me any info.


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