Step 5: Eli-Kart: Electronics
Anyways, Kelly controllers have connectors for pretty much anything you would ever need. Reverse, regenerative braking, even brake lights and a beeping sound. I neglected to use the connectors it comes with and soldered my own .1" headers onto the connections I would use. I would recommend soldering the connections once you know everything works, but tape works well for making sure they don't fall out until then.
One downside to this type of controller is that you need to have sensors on your motor to allow the controller to detect its position. Read into the custom motor section if you want to know more about this, but you'll essentially need to either take apart your motor and put in sensors or use digital fabrication to make a sensor mounting board. The alternative to this is to use a sensorless controller. These will require a little push-off to prevent your controller from exploding on the inside, so keep that in mind when designing your vehicle. You can pick up cheap sensorless controllers from Ebay. They are surprisingly legit as proved by Charles, though I would recommend this one.
At the bottom of the food chain are brushed DC controllers, which can be cheaper and easy to use. Kelly Controls also sells DC controllers, or you can go with scooter parts. This might be a good option if you want to save money and time but don't want to go sensorless, or if you already have brushed motor lying around.
Batteries are the I made my own custom battery pack out of A123 26650 cells, combining 12 in series and 3 in parallel for a 39.6V 7.5Ah pack. Unless you have your own personal stock of batteries, you'll need to buy some. You can find batteries online at places such as All-Battery, Amazon, and HobbyKing. I would avoid using lead-acid batteries due to their low discharge rate and poor lifespan, but be careful if you go with Lithium Polymer batteries such as the HobbyKing pack I linked. You will also need a battery charger. I have a 0-40V charger with balancing and a generic power supply, but if you know exactly what you will be charging you can get cheaper solutions such as this or simply a power supply.
You'll need a soldering iron to make the wiring connections, and thick wire for the main power connections as well as thin wire for the signal connections. Feel free to color code your wires, and label them if at all possible to avoid potential electrical headaches. Don't forget connectors as well: T-style "deans" connectors, bullet connectors, or XT-60 connectors should be all you need (just don't plug or solder anything in backwards). Digikey is also a good supplier for anything electronics related if you're not ordering parts from HobbyKing since they have free, faster shipping.
Basically, you get what you pay for when it comes to electronics. Brushless systems with a quality controller and Li-Ion batteries will give you the most reliability and best performance, but will run you around $100 per component. Lead acid, brushed components are probably around half that, but the motors aren't any cheaper and offer much less power.