Hackentosher

I believe so, I've taken a bit of a hiatus from FPV because of school and lack of interest so I'm not really sure. Knowing the developers of the Helio stuff, I'd imagine it's still going, but again, I haven't been following the industry.

If it were me, I'd get some ATTiny85 boards and some TP4056 boards

Yeah don't do that. They are more dangerous when they are fully charged because there is more energy in them that can cause problems, and it damages them chemically so they wont work as well when you need them later. Storage voltage for lithium cells is 3.8v per cell, so drain them to within .05V of that is my rule of thumb.

Some adafruit feathers do, I would use one of those anyway because they are more compact.

You can use arduinos as HID (human input/interface device), so all you'd have to do is wire your switches to the digital io pins, and maybe have a pull up resistor on each. Hell, you might be able to get away with the internal pullup called in the IDE. That should work great for what you want. There are a gazillion different arduinos of various size and functionality that would allow you as many or as few buttons as you'd like.

Damn that's pretty impressive, great work.

The @16:9 and @Cannon Lake are right, I jumped the gun on recommending a more serious tool. You don't need it, but it's a quality of life upgrade for sure. If you're just starting, it's not necessary, but if you get more serious about soldering and working with more serious and sensitive components, it's a necessity. Being able to control the temperature is great because if you are working on small stuff, you don't have to worry about over cooking stuff, or if you start working with some really heavy stuff (idk, 8 AWG wire or something) you can crank the heat up to give your iron more thermal momentum. There's something to be said about buying nice tools (and it's oh so worth it and satisfying) as they make your life easier, but my mentor once told me that if you learn to do something well the hard way, you'll be really good at the easy way.

No I mean jobs around the neighborhood or for your parents.

Find some jobs, I bet you can if you try. It's so worth it to spend some money on an iron. Even get a fakko on ebay, maybe $30-40.

If you're serious about electronics, get a soldering station. Temperature control is very important as you get more advanced, so spend the $40-60 to get a station. If you're really serious, get a Hakko FX-88D

Yeah that's not a great idea. You would double the capacity of one of your 1s cells which wouldn't really do anything. As one of the single cell cells drains below an acceptable level, while your doubled one would still have a good bit of energy left. However, the bms Will kill connection to the battery. It's not a good idea to mismatch capacities in a pack like this. Either leave it stock or do a 3s2p pack.

That 4056 module is a great little charging module, but you gotta keep an eye on it sometimes. Check in on the final voltage of the cell and if it's charging over 4.2v, throw it out and get another. You can use those for a 2s pack, you just need one 4056 module per cell in series in your pack. Simply set it up so that each module will be connected to the positive and negative of each battery so that they're only charging one cell and not the other.

Follow the data sheet from the manufacturer of the IC, not a guide. As for killing the pi, the pi is built to be pretty resilient and has short circuit and reverse voltage protection so it should be fine.

Look at evwest.com. You can source really nice batteries from crashed Teslas, and they stock them.

AC is good for inductive motor loads and transferring power over distances under 300km. Everything else really should (and in most cases can) use DC. Motors rely on the switching to turn and the frequency sets their speed. Household air-conditioners or pool pumps are good examples. In power transmission, AC is more effecient at transferring power because the voltage and current pass through 0, however the skin effect starts to come into play around 300km in high voltage transfer lines. I found a study by Siemens that found up to 9% of the energy passed through a 1200km AC line was lost, thus HVDC lines are commonly used for high power long distance transfers. 9% may not sound like much, but when you're transferring power on the gigawatt scale, you're losing a whole neighborhood worth of power just in the wire. I work at a lab at my university and I'm currently helping test power supplies and devices running on DC voltage as we are trying to make a DC microgrid with DC actually at the outlet, but point of use modified sine inverters for where AC is absolutely required. It makes more sense to run on DC because you lose power in rectification, and in inverting the power from generation. My coworker actually put on a cool demo where he created 100v DC with some bench power supplies and plugged it into a Dell monitor. If you think something needs AC to run, think about how it works. If it's electronics, you're not sending AC through the circuitry and microcontrollers. No way. If the device is electromechanical, it may need AC, but chances are it doesn't.