Mobility scooter

[Si&Oll]

good evening,
My 10 year old son and I are trying to convert an old mobility scooter into a go cart!
There isn't any electrics on it currently other than the motor (24v)
I have 2 batteries that came with the scooter also
I have bought a twist throttle handle bar thing with 3 wires coming out of it -don't mind if we don't use this
Please can someone help me as to how I can wire this scooter us with a variable speed?
Any help/advise will be greatly appreciated
Thanks
Simon

 

[Gryd3]

good evening,
My 10 year old son and I are trying to convert an old mobility scooter into a go cart!
There isn't any electrics on it currently other than the motor (24v)
I have 2 batteries that came with the scooter also
I have bought a twist throttle handle bar thing with 3 wires coming out of it -don't mind if we don't use this
Please can someone help me as to how I can wire this scooter us with a variable speed?
Any help/advise will be greatly appreciated
Thanks
Simon

How far down the rabbit hole do you want to go?
You can DIY anything here and custom build any circuit you want... but ideally the end result will be:
- Motor
- Motor Controller (Important!)
- Power Supply
- Throttle

The motor controller is the most important part here... This is responsible for bringing everything together. Battery, Throttle, Motor.
You can buy pre-made controllers, or build your own but we need a part number for the motor to find the maximum current draw.
In order to vary the speed of the motor, the controller will most likely use 'PWM' (Pulse-Width Modulation) which rapidly turn the power on and off to the motor... Your hand-held electric drill does this, and you may be able to actually hear a high pitched whine or buzzing when you slowly begin to depress the trigger.
The next step will be interfacing the throttle to the motor controller. Some motor controllers don't simply take a 3-wire connection, although it *might*, we don't know until we see a part number.

So?
Do you want to build from scratch, or find/buy a pre-made module?

 

[Si&Oll]

Hello and thank you for your reply
I would prefer to buy a pre made module but am open to any advice
The motor part number is 62001229
The ratio is 1 : 14.75
The serial number is 08000443
The mfg date is 28/03/08
Hope this makes sense and I look forward to your reply
Thanks again
Simon

 

[BobK]

PWM controllers are so cheap on Ebay, it hardly makes sense to build one, especially for the power level needed here.

Bob

 

[BobK]

You need to know the current draw in order to choose a controller.

Bob

 

[Si&Oll]

Thanks
Do I search for a pwm controller?

 

[Si&Oll]

How do I work out the current draw?

 

[BobK]

It should be labelled on the motor, or, you can measure it with a multimeter. The current draw will vary with load, so you would need to test it under load. Have you disassembled the mobility chair yet?

Bob

 

[Si&Oll]

Hi Bob,
Thankyou for your replies
The chair was already disassembled when we bought it
It's just a frame with a motor
There is nothing labelled on the motor about current draw

 

[Gryd3]

I've only been able to find eBay items with that part number... you may be stuck with measuring the current draw yourself...

To measure current, you have multiple options...
Option 1. Use a multi-meter or Ammeter and connect the motor in series with the meter. The meter may pop a fuse if it's not rated high enough.

Option 2. Use a 'shunt-resistor' . Buy a *very* low Ω rated power resistor. Connect this in series with the motor and then use a multi-meter or voltmeter to measure the voltage from one end of the resistor to the other. Using a little math, we can calculate the current draw.

Option 3. Last resort...
Charge a battery, play on it (without speed control) going around a tracks or something... time how long the battery lasts and estimate the 'average' current draw.
Once the average is determined, you buy a PWM controller rated higher than the average and if the controller does not have it's own protection, add a fuse in series to protect it excessive current draw of the motor.

Option 3 is a last resort... but is better than nothing.

 

[BobK]

To be entirely safe, you could just measure the resistance of the coils. This, with Ohm's law, would give you the stall current. A controller rated for the stall current would handle any load.

Bob

 

[Si&Oll]

Thank you again for your help
I have 'googled' the current draw for mobility scooter and most sites are saying 30A max so advising to go for a 40A controller - does this sound right?
I found this on eBay
http://www.ebay.co.uk/itm/10-50V-40...277587?hash=item3d14c23793:g:sccAAOSwr7ZW7BW6
Does this look right?
Thank you again
Simon

 

[Si&Oll]

This is the same motor as mine
http://www.ebay.co.uk/itm/BARGAIN-s...398213?hash=item1a155a7045:g:gdEAAOSwBvNTquBQ

 

[BobK]

The problem is stall current can by 5X the running current. Your controller says 60A max and 40A continuous. I might go a bit higher, like 100A max if the cost is not prohibitive.

Do you have an Ohmmeter so that we can determine the stall current?

Bob

 

[Si&Oll]

Hi Bob,
Thank you again
I have found this on eBay which is 100amp.....
http://www.ebay.co.uk/itm/381606139801?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT

Will be this work?
Thanks
Simon

 

[BobK]

I really can't say. I take it you cannot measure the resistance of the motor?

Bob

 

[Gryd3]

Hi Bob,
Thank you again
I have found this on eBay which is 100amp.....
http://www.ebay.co.uk/itm/381606139801?_trksid=p2060353.m1438.l2649&ssPageName=STRK:MEBIDX:IT

Will be this work?
Thanks
Simon

It may... but it depends.
Measuring the coil as Bobk suggested is ideal... using the resistance and expected voltage you can calculate a worst-case current draw. You won't normally run at this... but you may reach it, at least momentarily.

If most sites suggest 30A draw, you should aim for 4x that draw and use 120A ... if you are 'cautious' then you can use much less... but this caution essentially means "don't get stuck/stall, and don't accelerate too hard".
The highest current draw will be when you are at a stand-still and want to start moving.

 

[Si&Oll]

Hello
I do have a multimeter so can measure it
Please can you advise on how I do this?
Why setting should my multimeter be on?
Thanks

 

[Sadlercomfort]

Set your multi-meter to the Omega symbol 'Ω'.. You might only have one Ω setting, but you could have a few Ω settings with multipliers. In that case set it to a low Ω setting such as x1 or 200.

Disconnect the motor and measure across the two connections.

Include a picture of your multi-meter if you need more help.

 

[Si&Oll]

Good morning
I have measured across the 2 motor wires and have attached a photo of my multimeter
Does this look right?