I hope I can help answer- let me know if I'm stepping on toes Kieth.
wheelsmithy (Joe-with-an-L) said:
-how to make my own batteries. I see a lot on electric bicycle YouTube stuff where people weld/solder cells together, shrink wrap the whole mess, and put that in a steel box, and it is supposed to be weather proof (ie, won't burn the vehicle to the ground).
For our purposes as hobbyists, to build your own battery you need:
- A lithium spot welder. The only 'real' difference between a lithium spot welder and a normal electronics spot-welder is that ones made for our fiery boys should have the ability to alter millisecond pulses, amperage of the weld, and use IGBTs instead of a transformer for excellent control. Good cooling is necessary- spot welders are easily made,but they need to be able to handle a lot of current and you're typical Chinese kit (NOT the K-Weld) need modification to really work well.
- Current conducting strips. The current (heh) meta for eBiker's is the "Copper nickel/steel sandwich"- basically, nickel strip was the compromise metal for batteries because it was the only one that had the resistance to allow itself to be welded to cathodes/anodes; copper is too conductive, and could only be attached via solder (which can put too much heat into the electrolyte and make it boil, damaging the battery). Hobbyists however found that you can "Sandwich" copper onto the terminals by using a resistive metal to force it to the head. This also has a secondary effect, as copper acts as a great heat-sink on the batteries.
- A BMS. You don't NEED one, but to be frank, each person who claims they don't need a management system for a lithium battery is one easily preventable fire away. A BMS Keeps them from over/under discharging like a fuse, and tactically drains cells to keep them consistent. Many now also act as your % meter for lifespan and some super-advanced ones can even tell you when it's time to replace the pack itself.
- Kapton tape, or some other heat and electrical resistant tape.
- Some kind of glue to hold them together. Hot glue is fine, so is silicone sealant. Some makers even fully pot the batteries in epoxies.
- A case. Some make metal boxes like you said, but really shouldn't. Water-resistant, gasketed plastic boxes are best for starting and can be easily bought from hammer stores. Some companies like Lunacycle fully pot the battery in epoxies and some people have posted their formulas online.
-What about controllers? How do they work in layman's terms?
Controllers are for DC motors, Inverters are for AC. Controllers combine voltage regulation and give it in a form of sine wave to form the magnetic field through 3-phases- pure sine is the most expensive and best seen with controllers like with Grin Technologies, whereas modified sine is cheapest but tends to have less power, torque, more heat and more noise. Those are typically your Amazon specials. Pure sine also tend to be much smaller.
-Wattage, Voltage, etc. Are cars 24V? Break down why a car battery gives a very mild shock, but an electric car is full of deadly High Voltage.
Car batteries are low voltage, high amperage and your skin is high resistance. Electricity is like water pressure, its trying to reach an osmosis or "Base" level where it doesn't want to move anywhere. Eventually, as you pile on volts for more "speed" or "pressure", it'll overcome that resistance and you will become the easiest thing to go through. All safety with batteries is becoming the hardest path.
Voltage in DC (and partially AC but I dont understand frequency yet) directly affects speed. You CAN use transformers to increase voltage at the expense of amperage- like in your microwave- but without amps, you lack physical "oomph" to move things. Electric cars get around this by going ~400 volts (because your industrial 3-phase power is at 440v) and getting huge amperage for huge power almost as a side affect. That way, you have no efficiency losses and a drained battery in an EV doesn't feel slower than a full one.
-Safety. What is there to be afraid of (when doing a DIY electric car)?
Being the easiest way to the ground. Activating and testing a motor without it being secured to the ground AND without modifying voltage (Brushed DC runaway is NOT fun). Not being well-fused.
-How does one get weight down?
You want to do this also for efficiency, but the shortest distance from battery exit -> Inverter/controller -> Motor is best. There is a reason why the Nissan Leaf inverter is practically apart of the motor housing, and the same with Tesla- 400v+ and thousands of amps makes TONS of heat in cables no matter how well they're made. Use packaging to your advantage.
Next, cooling for batteries. They really need refrigeration, but they also don't run at "pressure"- a Tesla Y maybe runs it's coolant system at 1PSI. You could easily use plastic for hoses, and their heat exchangers tend to be smaller than radiators. Know that they don't/can't use a car radiator well as batteries don't like 100F+, and their coolants use sillicone bases instead of the salts in our standard ethylene glycol (which is also more conductive).
-Know anything about the new "glass" batteries that are supposed to be a revolution for electrics?
Nothing super-new from Mr. Goodenough. Everyone's focusing on Sodium-ion from India and CALB, and the "We totally got it now! honestly! any day now!" goal of solid-state batteries.
-Tell us more about hot rodding an existing motor. Can I just feed more electrons to that wrecked Leaf motor?
In essence yes, but eventually the electrons going the other direction in the field- called "Back EMF"- will become too much. You'll get too much heat, or it might lock the motor because it cannot overcome the field. DC on the other hand...
-Are batteries as poisonous to the environment as I imagine? Are electric cars simply the methadone to get us off our heroin (gasoline) addiction?
I'd have to pull up articles to prove this, BUT: The real 'problem' with a lot of lithium mining is, you're taking something out of the ground and you're not replacing the mass, so the ground literally sinks (just like in Germany with their coal mines). You have mining runoff but it's not much different from mining nickel and every other metal; the one heavy metal that DOES give issues is Cobalt, but Tesla gets theirs from Canada and that's only for a specific form of Lithium-ion. If you're using Lithium Iron Phosphates, you're literally using farm phosphates, lithium salt, and iron. You could genuinely mine all of that out of a junkyard.
Basically- the mining is overblown, especially versus Petroleum. It IS still a problem. Disposal is a worse issue, but more because the electrolytes (even when fully spent) can still oxidize and start fires. Recycling lithium batteries now is because it is a cheap way of getting 99% pure metals.
-Is there any need for gearing (I know transmissions are unnecessary)?
If you call a Diff gearing- AC yes, DC maybe. DC spins at slower speeds and has more off-line torque, but AC has WAY more options available and doesn't loose speed and power with low voltage. Typically, most EV vehicles are at a minimum of 6:1 reduction. Teslas are 8:1 or maybe 10:1.
2-speeds can be a good idea for them, if you can keep efficiency up (like using a Lenco box) and can run the trans in reverse.