Power Generation

Recharging an EV is the biggest problem with batteries, they take a long time to charge or you do significant damage to their over all lifespan. This is the simple reality of it, it has to do with some of the more basic laws of physics & electricity that I certainly will not be figuring out how to change.

So if I accept this I have options. Let's deal with a smaller battery than the one in someone's Tesla or Volt. We'll use my eBike battery because, it's what I'm most familiar with. The battery takes power in at a higher voltage than it puts out energy & it takes it in at 1.8 amps. That amperage is the controlling factor in how fast your battery charges. My battery is 500 watt hours & from "dead" (which is still more than 8% "juice" left in the battery) will take about 7 hours to charge. Now if I were to step the amperage up to 3.6 amps I'd charge the battery in about 4 hours, maybe less & doubling it again would cut the charging time to about 2 hours. Each time I charge it at double or quadruple the rate that's ideal it is as if it went though 2 or 4 charge cycles & I'd lose 40-150 miles of range off the end of my battery for each such charging. Now, let's focus on what matters about an individual battery in a system. We can use a single battery to get 36 volts or we can use 3, 4, 6, 10 or more depending on the voltage of each cell & how we array them. We can use 1 battery to get 20 amps of power to our machine or we can use several. That several is what is interesting me now. If we use several batteries then each can be charged at the same time. So we can either charge the battery 4 times faster than it wants or we could cut the battery in to quarters & charge each cell individually. The ability to charge multiple cells individually creates the potential for power generation as you ride to be a useful thing. It has been the reality of things that you simply ran energy out of the batteries far faster than it could possible be replaced. That 500 watt hour battery on my bike can easily be depleated in 2 hours of hard riding & might last for 4 hours of frugal use, but will take every minute of 7 hours to charge. Now we're talking about 4 cells that each could be charged in 2 hours & that works remarkably well.

This leaves us with the best ways to gather that much power in 2 hours. Solar is not quite there, wind has some potential but, there's the reality of no such thing as a perpetual motion machine & drag may outweigh any potential benefit to using the ample windpower available. The idea is that with me adding energy into the system perhaps I can make it a net win through overall efficiencies.

A small turbine seems sensible with an equally small set of generators, the issue is building such a system.

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Comments (7)

  1. noahbody

    And added weight. Weight has to be a factor too.

    Interesting problem. I like the 4 cell approach. But can you charge them while they’re in use? That is a good question.

    December 20, 2016
    1. Munkyman

      yeah if you’re using 2 at a time for voltage & then adding 2 more for extra amperage when needed. You can be charging those not in use.

      December 20, 2016
    2. Munkyman

      You can also manage your time better by only charging to 80% & beginning the charge cycle when a cell hits 40%.

      December 20, 2016
    3. Munkyman

      Weight is one of the reasons, wind is desirable, you get more watts per gram of machine weight than just about anything else. Solar gets heavy quick plus it’s unreliable & then the turbine is the next lightest solution, I got turned on to wind because in India they have a car that runs off a compressed air turbine.
      If you use a fabric sail for your blades & lay it down for a helical turbine inside a tube to get more aero-dynamic & to get more force off each molecule of air that passes through. Next you use a carbon fiber mast with magnetic levitation collars at each end to reduce friction in the machine while maximizing the friction with the air flowing through. The issue in my case is what will the generator weigh that is capable of generating 42 volts DC at 1.8 amps for 2 cells at a time. Weight of generator & w/e transmission it will require between it & the rotor shaft/mast.

      December 20, 2016
  2. fuall

    The EVs of today use a variety of battery technologies, but the first ones were series parallel lead-acid batteries or packs made of hundreds of ‘C’ size Ni-Cads. You won’t be able to return any useable amount of energy from the bike back into the batteries. There is too small of a current to push into the batteries while it is being divided to also do work running the bike. And no, you can’t charge them at the same time. The current through the battery would damage the internal plates and burn up the battery. Same for forcing the battery to charge faster by increasing the charging current. Yes, it will go faster, -up to a point. And that point is where it catches on fire. Unfortunately there’s really no way to tell EXACTLY where that point is on any individual battery and/or charger until you’ve reached it, and then it’s too late.
    As for how long your battery will last, that depends on a few things. What type of battery, the size of the battery, and the composition of the battery to name a few. They’re rated in Ah and you really need to know how much work you’re going to need to do to know what battery and what size will be required to do the job. Generally speaking, there aren’t any 42v batteries, and to get there you will have some smaller division of batteries to make up the total. That is where the charging is done, at a lower level. By using series-parallel banks of batteries you can get whatever voltage you need at whatever current you need. But you still have to know what you’ll need to know how to get there. You’ll also have to consider the available options for charging your batteries. Theres no sense in getting 24v batteries if you only have a 12v charger. But you can get 24v from 12v batteries and still be able to charge them.
    Don’t know what you’re attempting to build, but good luck on the carbon fiber. That’ll be more costly than ANY part of the power or charging systems, and I don’t even know ANYWHERE you can actually purchase off-the-shelf mag-lev pillow blocks at ANY price. As far as the air car is concerned, (I saw one of these a year or two ago and they promised it would cost about $3k, which sounded pretty optimistic at the time) I am assuming there is a compressor installed along with the appropriate batteries to operate it, which would extend the range considerably. It may be possible to maintain sufficient charge to operate the compressor for extended periods if not indefinitely, up to the life of the battery, with an additional battery bank and a solar collector. We would really, again, need to know the amount of work needed to be done, i.e. how much compressed air is needed and how much power to operate a compressor capable of providing that amount of air.

    December 23, 2016
    1. Munkyman

      I have a friend who works in carbon fiber, another in titanium & the reality is I probably’d be better off with a graphite mast/drive & ceramic bearings would be good enough with paraffin lube for any sort of prototype horizontal turbine windmill. The voltage I need for a 36v battery is about 42v & to fill them at their desired rate would take 1.8 amps, these Lithium batteries tend to charge fastest between 20% & 80%, that last 20% seems to take twice as long as the 20% before it. My gripe right now is that I know I generate a lot more energy than the battery can take when I am using the regenerative breaking & I’m pondering ways of putting the energy into an interim storage that can hold it as fast as delivered & then return it to the motor as soon as it’s needed. I think the same storage cell could be able to fulfill a very desirable goal of being able to shove 5-10 miles of power (about 100 watt hours) into the bike in under 5 minutes.
      I realize the issues of a perpetual motion machine, but the question is can I provide the difference between current range & doubling it by harvesting every last watt I can scrape together. I learned early on you can’t & really don’t even want to charge while burning a battery, it’s better to bypass the battery & go straight to a capacitor in front of the motor for energy efficiency. I have this logic chart forming in my head & I have another friend who’s a DC/solar electrician that I hope can help me flesh it out as existing electrical parts. The long term goal is a 200 mile a day touring bicycle.

      December 23, 2016
  3. prair1929

    Power generation is one of the concept on which many devices are made like generators, batteries, cells and other such power generating devices. In order to understand the concept please visit the website with the address that is www.aussieessays.org as it is complete website on essays writings.

    February 10, 2017