8 ms·

Batteries are rapidly improving (on many metrics, but the relevant one here is increasing in energy density). The range is apparently 125 miles electric, and 5

• ActorNightly 13d ago
  Batteries aren't rapidly improving. Every single battery that has proposed higher energy density also has downsides in max discharge current. We may get at best like 10% improvement over what it is today.
  • enquirewithin 13d ago
    It’s taken thirty years for lithium batteries to double in energy density, and the rate of increase has tapered off recently.
  • aidenn0 13d ago
    That's max discharge current per cell though. You are going to have a lot of cells in a plane like this.
    • ActorNightly 12d ago
      To get high voltage, you need batteries in series, which means all the batteries see the same current. The only way to reduce current is to put batteries in parallel, which for a given voltage doubles the weight of the battery pack. You could go with lower voltage, but that means for a given, power, you need more current, which drops your efficiency.
      • aidenn0 12d ago
        If you are consuming X watts per cell, then each cell will drain by the same amount of current regardless of whether the cells are in series or parallel (or more likely a combination of the two). This is supposed to be able to handle "up to" 2-hour flights, and (for jets at least) takeoff power is about 3x cruise power, so about 1.5 watts per watt-hour of battery, or a 1.5C peak discharge rate. What chemistries are you thinking of that cannot handle this?
        • ActorNightly 8d ago
          You misunderstand what Im saying The full power system for a prop looks like this: you have a battery of a specific voltage, which then runs a motor, which then runs a gearbox, which then turns a prop. The motor and the gearbox can be considered as one unit - an electric motor has two factors, KV(RPM/volt) and KT(torque/amp). The higher the KV, the lower the KT. A high KV motor spins fast, but draws a lot of current for the same torque - putting it through a reduction gearbox turns it into a low KV, high KT motor. Naturally, low KV motors or (low KV setups) are more efficient because they draw less current for a given torque, and the heating power loss varies with current^2. The prop needs to spin at certain RPM for max aerodynamic efficiency. Given the slider for motor/gearbox selection between high KV/low KT and the opposites, you generally want to have as high voltage as possible, so that you can run a low KV/high KT setup, which means that for the given torque, the current is minimal. I.e you have a motor spinning really fast, through a large reduction gear, driving a prop at the necessary speed and torque without much load on the motor. So lets say you determine that you want a certain voltage, which requires a stack of cells in series. The only way to get more capacity is to duplicate that stack and put them in parallel. So your weight becomes quantized by the number of stacks you have in parallel. And the more stacks you have in series, the higher the weight jumps between parallel stacks counts. Subtracting cells from stacks doesn't work well. Lets say you have a single stack of 10 cells 10s1p. If you do something like 8s1p, you lower the output voltage, which means you need to have slightly higher gear ratio to spin the prop at the same efficient rpm, which means you draw more current, which means the extra capacity in the cells doesn't really matter if you are drawing more current.
          • aidenn0 8d ago
• mjcarden 13d ago
  Canberra - Sydney is one of the busiest routes in Australia with Dash 8 and ATR turboprops on high rotation every day. I could see a small electric aircraft working pretty well there, modulo charging times.
  • defrost 13d ago
    > modulo charging times. There's already an Australian electric trucking company trailing plug n'replace heavy battery packs (with a forklift). That allows for fast turnover times while used batteries recharge at terminals.