MY ELECTRIC SCOOTER
Powered by a "PICAXE" microcontroller chip.
So what's in it?
1] Hall effect throttle.
2] 24 VDC, 18 Amp, 450 Watt, permanent magnet, brush DC motor with a 4.5 to 1 onboard gearbox (approx. 2500 to 550 RPM)
3] Uses 1/2 inch or approx. 12.7mm pitch bicycle chain.
4] Two 12 Volt 18Ah SLA glass mat batteries electrically in series.
5] A PICAXE-08M chip using the Pulsed Width Modulation feature. (required program is only a few lines of code in "BASIC")
6] Main power MOSFET module are available from Jaycar Electronics here in Australia. Part No. SY-4086. Requires 3-32 VDC input, switches 30 VDC @ 100 Amps max. I drive it directly from the
PICAXE PWM output.
7] 35 Amp bridge rectifier as a kick back or flyback diode.
8] 30 Amp, 24 Volt horn relay used for full battery isolation i.e.. safety. (yes, I'm paranoid!)
9] High intensity LED's for lights. Red LED's - rear light, White LED's - front light.
10] Onboard meters, 0 - 35 Volts & 0 - 10 Amp meter.
11] 24 VDC, 10 Amp battery charger (29.5vdc) It's just a simple bare bones un-regulated battery charger.
(new pictures at the bottom of this page)
Electronic and Electrical Schematic PICAXE-08M E-Scooter Code LINK to the PICAXE-08M Electric Bike
THE NEW 16 TOOTH DRIVE SPROCKET
(twice the speed now! but half the torque.... but it still has lots left!)
The 29.5VDC Electric Scooter Battery Charger
The Main Scooter Transistor.
it has a very slow on and off time, it's being pulsed at only 250Hz.
Some final thoughts...
It's 99 percent done! (finally!) The last thing I'd like to do is put some high intensity white LED's on the front for lights while I'm still motivated. (done) It's probably something I should do if I decide to take it out at night. I believe there is also room for changing the sprocket ratios. (done) It has lots and lots of torque. It will easily pull a wheely if you hold the scooter back and apply the throttle while on a surface like concrete where the back tire can get some traction. Otherwise, the back tire just spins. Presently it only goes about ...... I guess 12 Kms an hour? Only a guess. I'd like to sacrifice some torque for a few more Kms. an hour.
One other thing I noticed but didn't plan for. If I take off down my street on full throttle, the scooter rapidly ends up going faster then the motors rated rpm and appears to start dynamically braking of some sorts??? As long as I hold the throttle pretty much wide open it feels like it's some what dynamically braking but I have not put anything in place to short the motor terminals into any resistance for dynamic braking. Possibly it feels like dynamic braking but it's really regenerating as the motor, now generating a voltage, is greater then the battery voltage and it is trying to charge the batteries while going down hill? Just a thought. Regenerating.... I think that's the right word.
And last, just a word of warning.
These 12 volt, 18Ah. SLA (sealed lead acid) glass mat batteries in this project are very interesting. They appear to be a bit different to the older sealed "gel cell" batteries. The manufacture of these SLA glass mat batteries claim the following ratings: 1 amp for 18 hours or 18 amps for 1 hour. What's so interesting, and impressive, is the third rating they spec. 100 amps for 5 seconds! So, unlike the older gel cell batteries, these SLA glass mat batteries can deliver everything they got in just a few seconds!!! So when you series two of these batteries for 28 volts at 100 amps, well..... that's some electrical ratings that arc welding take place at. So if you accidentally drop the exposed metal portion of a Yellow, Blue, or Red insulated spade type crimp on lug across the opposite polarity, it magically disappear before your very eyes!!! Personal experience;(
So.... beware and be safe.