Well, there are only three possibilities. It's the motor, the batteries, or
the controller. How mini is the mini-bike? I have a small scooter/mini
bike that came with a bad controller. I ditched the controller and
installed a single contactor. Now I just switch in either 24 or 36 volts
worth of batteries. Even with me on it it will do at least 15 mph at 36
volts and I am North of 250 pounds. I have not counted the teeth on the
gears so I'm not sure what the ratio is set at, but everything about your
setup sounds heavier duty then what I am talking about. I would try hooking
some batteries straight across the motor. If you can, start with 12 volts
then try 24 volts. Just use a pair of jumper cables and don't ride very
far. 36 volts is starting to push it a little high for the jumper cable
approach, but if you have a decent contactor laying around you can also try
36 volts. A clamp on ammeter would be great if you have one, then you can
see how much current you are drawing. A voltmeter across the batteries will
also give you useful information.
A 750 watt controller sounds like plenty to tool around on a minibike, but
it is the easiest thing to take out of the loop, so I would start there. I
would expect you to be able to do at least 20 mph on 36 volts on your
minibike, but you may find that the motor needs a lot more current then the
20 amps or so your controller can provide.
damon
From: SteveS <[EMAIL PROTECTED]>
Reply-To: ElectricMotorcycles <[email protected]>
To: ElectricMotorcycles <[email protected]>
Subject: [ElectricMotorcycles] mini-bike performance
Date: Sat, 23 Jun 2007 15:04:50 -0400
Or lack thereof.
The volume of emails lately on the list served as a good kick in the can
for my mini-bike project. I finally wired it up and tried it out. It was
not a great experience.
The power was very low and then the motor shed part of one magnet. Luckily
I had another motor and put it and tried again. Still not working well. On
flat ground I can get it to move along maybe 3-4 MPH after helping it start
up. If I start on a downhill I can get the speed up to 5-7 MPH but it bogs
down on any uphill slope.
Here's what I have.
Mini-bike frame with 11" rear tire.
Motor gear 12 teeth, rear gear 64 teeth
~1HP 36V large mower deck motor from an Elec-Trak
3 12V-18AH SLAs in series
36V 750W controller from a scooter store
If I calculate right at 5MPH I should be turning about 800RPM. Maybe I need
a higher gear ratio? The motor is probably designed to run at a constant
speed since it's from a mower deck. Could that be the problem? Or am I
just asking too much from too little? On the flat it was pulling about 20A
or so.Voltage stayed pretty steady. Batteries are new and freshly charged.
It is a pretty heavy setup with the motor, batteries (and me!).
I didn't expect too much, but I thought it would move along.
- SteveS
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