Hi everyone
I just want to say what a wonderful forum this is, this is my first post. I am looking to build a slider throttle that is a variable resistor, but was wondering if anyone has come across such mechanisms. I know that the older golf carts used them in prehistoric times but nowadays everyone seems to be using controllers.
I don't have the bread for a controller so have been considering building this alternative
i would be very grateful if you could guide me on the build. 12v = slow, 24v = faster , 36v = a lot faster, 48 = hyper speed
need a little more information,
do you know what motor you want to control?
if you do, can you give more details?
sounds like a contactor controller may be the go,
but it really depends on the size.
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
If you really want to use a variable resistor as a throttle, it's going to be fairly hefty in size and weight, and expensive if new (though they can be had for free if you dig thru junkyards).
You'd be looking for something like the one I posted here:
http://endless-sphere.com/forums/viewtopic.php?p=205189#p205189
A better, more efficient way is with the contactor setup mentioned above. Many old golf carts and forklifts used such a system; you might be able to get one for next to nothing, and typically they ran on 24, 36, or 48V depending on the usage and design. There are even some electric cars that have been designed with such a system, like the CommutaCar.
--
Michael Elliott
Cybernetic Necromancers, Discorporated
Phoenix, AZ
Watch me build an electric-assisted recumbent bike from recycled junk:
http://electricle.blogspot.com
A variable resistor is very inefficient. At half throttle, you're throwing away half your power as heat -- and at 10% throttle you're throwing away 90% of energy.
And that heat has to go somewhere. So for example, if you were operating at a max amps of 100A @ 48 volts and were at half throttle, then your system would be throwing out 50A @ 48 volts = 2500 watts of heat. That's more than a home space heater's worth of heat that's getting wasted and needs to get discharged somewhere -- hopefully not near any of your body parts.
Not good.
Use a good PWM (switching) controller like the rest of us.
Karen
Working on a Piaggio Boxer (mo-ped) EV conversion: http://gpsy.com/ev
And as Karen said you would be throwing away a lot of energy. A controller is not only a a big light dimmer / speed controller it has recovery diodes to recover energy put into the motor. Otherwise known as flyback diodes. Depending on how long you want to wait, there are lots on eBay and other sites at a steal. Too many people have re-invented the resistor method and it has proven itself to be a total waste of energy and time. I have got a few PWM's on eBay for under a $100.00 rated at 48 volt and 400 to 550 amperes.
You said you don't have the bread for a chopper? The money you spend would be a total waste as using a resistor. Most of the time my tractor uses 40 to 50 battery amperes and motor sees about 100 to 150 amps. Now that is recovered energy. Same thing I saw on my S-10, 144 volt system. So on a small application you can still see gains.
Rusty
KB1UKU