Solar charge controllers

[Mike90250]

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so in order to prevent more current to flow, we need to add some sort of limiter which i dont know the name of it. right?

That's called a motor controller, and you need to include that in your budget, or else your kart will run like an electric slot car, with no rheostat, full on & full off. 20 mph or stopped.

[elkowalski]

hey mike the motor controller is it like this one?

http://www.electricscooterparts.com/speedcontrollers24volt.html

[Mike90250]

at least a 300 w model, that works with your motor. If you have a 6 wire motor and a 4 wire controller, someone won't be happy

[elkowalski]

yes mike i am going to buy the following speed controller
CT-811B9 24V 350W Electric Scooter Speed Controller
and from the same webpage
24 Volt 350 Watt Electric Scooter Motor

so i guess this will take care over the amperage that goes to the motor.

another question.
is there any way that you can make a solar go kart without the use of batteries? i dont care the speed of the go kart i am just hoping to get few mph or only be able to move it a little bit.

[Sunking]

so in order to prevent more current to flow, we need to add some sort of limiter which i dont know the name of it. right?

You have got things backwards a bit. What you need is a Motor Controller, and the type of controller you need depends on the type of motor used being either series or shunt wound. In your case it will be a series wound motor as it is the least expensive and they require a PWM controller.

Now here is the funny part, the object of the controller is to pump as much current as possible into the motor without burning it up. You are now starting to discover all those little secrets I warned you of. There are still more for you to discover. A inexpensive PWM motor controller for 24 volt motors is going to set you back $200 or more like this one available on E-Bay reconditioned for $175. It is made for 24 volt small electric motors and provides 300 amps.

Remember what I told you, an electric DC motor does not work like you may think. At 0 RPM they require very large currents to develop torque, and without torque you have no acceleration. As RPM rises the current tapers off as the voltage comes up. when the voltage and RPM hit max limit current, torque, and power = ZERO. In a DC series wound motor current and voltage vs rpm are inversely proportional, and maximum power is delivered at 50% RPM of the motors rating and voltage.

Lastly i have this strange hobby. I race golf carts. To do that I have to modify them. I have one now and help a lot of friends to convert there carts. My little EZ-GO cart will go 35 to 40 Mph. No that does not sound fast, but it can accelerate from standing stop to top speed in about 10 feet. It pops wheelies, burns rubber, and will climb a tree.

I suggest you rethink your design, because what you are trying to do is not going to work. It could work you would see solar powered cars and golf carts. There are none, at least not in the way you are thinking. A battery solution is to build a standard electric cart using batteries > controller > motor and leave the solar panels off it. Us the solar panels to charge the batteries, but not install them on the cart but as a separate stand alone system. It is the only way to make it work.

Now here is the sad part. Remember my custom golf cart. The batteries are the exact same batteries in every golf cart. I just replace the controller, wiring, and motor. On a full charge I can get around 20 miles to 50% discharge or 4800 watt hours. To charge my cart if I used solar panels and wanted to do it in one day from sun up to sunset, it would require about 2200 watts of solar panels, and a 60 amp charge controller. 2200 watts of solar panels takes up around 13 square meters of space or rougly 6 feet wide x 20 feet in length. So as you can see it is not physically possible to fit enough solar panels on a vehicle to power it. Nor does the economics make a lot of sense either as the panels would only generate les than $1 of power each day to run the cart for about 1-hour as the panels and controller cost are around $4700.

[elkowalski]

well sunken after reading all that, what would you suggest to do for a solar car mini project? the professor is giving me all these ideas and i am just trying to get something out of it. i dont want to run not even 10 mph i just want a go cart that will have 22 pounds of solar panel weight (2 45 watts in series), 2 batteries (24 pounds) and i guess everything together with the weight of the boy will raise to maybe 160 or less. i understand what you are saying and i am not planning to keep the solar go kart running for a long time just 5 minutes of running and then a completely stop time of 10 minutes. and in order to start the go kart i am planning to gather a group of kids to push the go kart so that it starts to move just like an electric scooter. i am planning to use these speed controller to kind of limit the current that goes to the motor

CT-811B9 24V 350W Electric Scooter Speed Controller

this is the webpage

http://www.electricscooterparts.com/speedcontrollers24volt.html

i am pretty sure it can work with the whole list part that i talked about before. i just need mike's and yours green light to begin the project that will end in 6 weeks. i know that you guys are the right persons to talk to thats why i am trying to gather all the tips and ideas from you and put it into practice for this small project.

if you have another idea of how to make it work with parts alike and including a solar panel on it it will be of great support for us.
the design is a solar go kart that actually have a solar panel mounted on the go kart thats why i cant take out the solar panel from the go kart sunken.

[Sunking]

CT-811B9 24V 350W Electric Scooter Speed Controller

this is the webpage
http://www.electricscooterparts.com/...ers24volt.html

Now you are getting somewhere. What motor are you going to use. The motor and controller must be compatible. It is OK if the controller is slightly larger than what the motor is rated for in fact a good practice. But the topology must match.

As for a charge controller for 90 watts of solar panels the inexpensive ones are called PWM types and you would only need a 5 amp controller.

Scratch the charge controller idea, you do not really need it for this application, connect the panels directly to the batteries. You will need a way to connect and disconnect the panels very easily to control the charge and especially at night so the panels do not discharge the batteries.

Shoot for the largest batteries you can afford to put in of 15 AH or more @ 24 volts. If you have the budget shoot for LFP batteries as they have the higest energy per weight and volume, almost 4 times lead acid. In other words 4 pounds of crap in a 1 pound box.

[elkowalski]

Now you are getting somewhere. What motor are you going to use. The motor and controller must be compatible. It is OK if the controller is slightly larger than what the motor is rated for in fact a good practice. But the topology must match.

i am using a 24 Volt 350 Watt Electric Scooter Motor it is exactly rated at 350 as the speed controller but i am not sure if they are actually compatible i believe so because same company same webpage and thats the only speed motor for that rated current.

http://www.electricscooterparts.com/motors24volt.html

[QUOTE]Scratch the charge controller idea, you do not really need it for this application, connect the panels directly to the batteries. You will need a way to connect and disconnect the panels very easily to control the charge and especially at night so the panels do not discharge the batteries.[/QUOTE
what will happen if i connect the panels directly to the battery? would i lose more power?
yes sure i can use a switch so that i cant disconnect the panels.

Shoot for the largest batteries you can afford to put in of 15 AH or more @ 24 volts. If you have the budget shoot for LFP batteries as they have the higest energy per weight and volume, almost 4 times lead acid. In other words 4 pounds of crap in a 1 pound box

allright let me start looking around to find this kind of batteries. i cant buy anything from ebay since the school is providing the money and they need a real company that can give real refunds or so.

thank you sunken for these helpful tips.

[Sunking]

what will happen if i connect the panels directly to the battery?

The batteries get charged assuming there is ample sun light.

would i lose more power?

In a sense yes, but no more loss than a PWM controller introduces.

There are two possible bad things can happen by directly connect the panels to the batteries.

• Overcharge batteries.

• Discharge the batteries when the panels or shaded or at night. However this can easily be fixed by just adding a diode to prevent back feeding the batteries into the panels.

Since this is just an experimental toy that will not be used long term, and to save weight and expense you can omit the charge controller.

[elkowalski]

so i will keep the same configuration 2 solar panel in series right?

so i was wondering sunken, is there anyway to just use solar panels without batteries for a solar go kart?i am not asking for alot of mph i am just hoping that i can get at least 2 mph without the use of batteries . that was one of the things that my professor was telling me. that if we can make a solar go kart without batteries i know that for the start we will have to push it but could it work? if it can be done, what do i need or how does it work?