While the Electrathon America Handbook is our primary resource, here is some supplemental material that we will keep updating. To steal a quote - "None of us is as smart as all of us" so find us on facebook, twitter, instagram, linkedin and ticktock and ask questions, share projects, tips and lessons learned. We can all help each other learn! We will also include links to other resources, please share your favorite links with us at ElectrathonAmerica@gmail.com
Some of our favorite links:
-Electrathon parts - www.ShiftEV.com
-Ebike parts and CycleAnalyst instrumentation - https://ebikes.ca/
Power and Energy
Units of power are HP or KW. 1 HP = 747 kW. Voltage x Current = Watts (V x I = W). Energy is power over time or kWh. We average one kilowatt of power in a one hour race for a total of 1 kWh.
Note: 747 watts not kW "for a total of 1 kWh of energy used."
Voltage and Current
Electrical shock can be dangerous, so working with lower voltages is a big safety benefit. Electric vehicles can use 400 - 800 volt systems, most homebuilt cars are in the range of 200 volts, but lighter/smaller vehicles can get by with 24 - 48 volts. Electric bicycles use 36V, 48V, 60V and even 72V packs.
Wires and Connectors
Wire gauge (size) is sized according to the maximum amount of current that it will carry. There are sizing charts (here). Wire is heavy and expensive so the lightest gauge should be used for those reasons. Welding cable is commonly used for the drive system cabling. Wire quality varies with strand count (higher strand count is more flexible and more suitable for shock/vibration environments) and also wire insulation.
Connector pins and wire terminals can be crimped or soldered. Both are reliable methods if done properly, and the most important thing is strain relief (making sure the wire will not pull on the connection). Heat shrink is typically used on all terminations, and wire sheathing can be used to protect wire bundles (here). Here are some sources for various connectors and terminals. Some connectors require special crimping tools and pin extraction tools, but many use common standard crimping tools
Batteries and Charging
Electrathon cars usually use lead acid batteries. They are heavy but cheap and readily available, and do not require a Battery Management System (BMS) which keeps the designs simpler and also safer. Some lithium chemistries are very volatile and can be a fire risk if poor quality or if not used properly.
Physics (Forces, Energy, Losses, Friction, Aerodynamics)
Materials (Steel, Aluminum, Composites)
Most vehicles use steel tubing welded together. Some have used steel tubing with fittings bolted together. Aluminum is lighter but more expensive. Aluminum square tubing can be bolted or riveted together and some use round tubing welded together. Few cars are made from composites (fiberglass, carbon fiber or wood (the "natural . Bamboo has been used as a sustainable material.
Fasteners (Welding, Rivets, Bolts, Adhesives)
Cost and Schedule
Plan things out by setting a budget and a schedule. Start off a high level and keep breaking it down into smaller pieces like "drive system" or "rolling chassis". Try to estimate how many hours each task will take and keep referencing it to see how long things are really taking and then adjust things accordingly. Do the same with cost - price the big expensive components, then group small things into smaller categories like "fasteners" or "connectors". Try to think of everything required and account for it in cost and schedule. Even ordering parts can take more time than estimated. This is a very good exercise to get better at planning any project. Microsoft Project is a good computer application to use, but there are open source alternatives like ProjectLibre
Sourcing and BOM
It's good to keep a good parts list with sources, cost, weight and more. A "BOM" (Bill of Materials) is typically used to list everything needed. A Microsoft Excel spreadsheet can be used or other spreadsheet applications like Google Sheets or OpenOffice
The design rules should be well-understood from the start. There are many things that are important to electrical and mechanical design like the roll bar or isolation switch. Things like this may be harder to incorporate if the project gets too far without working them in from the start.
Schematics help plan the design, provide a reference when wiring, and allow others to review the design or work on the vehicle. It helps make sure all parts are accounted for in the BOM, and may save money by making mistakes on paper instead of damaging wiring and components.
Testing is not an after thought. It is addressed during design. Are there test points to check voltage or to help with troubleshooting? Are there lift points for the chassis? Is there instrumentation to show what's going on during a race? Think about what needs to be tested and how it will be tested.
Safety doesn't start at the races, it starts with covering electrical connections from accidental shorts and eliminating sharp edges and corners. Good safety practices are using protecting eye and ear protection when working, and checking that voltages are not present before touching or working on the drive system. It also means testing things well enough so that there are no surprises at the track.