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What generator should I buy for charging 12V battery?

  1. Apr 18, 2017 #1
    I have to charge a 12V 7AH battery using a wind turbine. For this purpose what kind of battery should I employ?
     
  2. jcsd
  3. Apr 18, 2017 #2

    phinds

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    First you ask what kind of generator to get and then you ask what kind of battery to get. Please make up your mind what your question is.
     
  4. Apr 18, 2017 #3

    jambaugh

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    I'm confused by your question in that you assert you have a 12V 7AH battery so are asking what type of battery?
    But I will assume you simply mean you need that many volts and that much stored energy. Those specs fit a sealed lead acid battery. A quick internet search pops up several such with those ratings for e.g. security alarms or security lights supplies. There are of course also in addition to the Lead Acid battery:
    • The Nickel Cadmium (NiCd) battery.
    • The Nickel-Metal Hydride (NiMH) battery.
    • The Lithium Ion battery.
    • The Lithium Polymer battery.
    To answer your question more precisely we'd need to get into more specifics of your application and priorities. You have unlimited funds? You need long life? You need high power output? Fast recharge rate? You worried about the environment? Is weight an issue?

    For simple and cheap and easy to recharge in a stationary application you're likely going to want to go with lead acid batteries. Most automotive batteries will supply well over 7Ah at 12V.

    In any case you ought to read up on the issues with recharging various types of batteries.
    The wikipedia article: https://en.wikipedia.org/wiki/Rechargeable_battery is pretty comprehensive on the various types and their charging issues.

    You'll want some bit of electronic control of the charging between the wind turbine and the battery since the turbine output is not uniform. At the very least you'll want a rectifier/diode to prevent the battery from discharging through the generator. You should also use some form of voltage regulation to keep the charging voltage from being too high (especially an issue for the more expensive lithium batteries) and there are cheap circuits that will up the DC voltage to the charging level when the supply is too low. There are a wealth of hits for any web search on the subject.

    And if you're willing to wait a bit, there seems to be a new battery coming down the tech pipeline. See the recent buzz about the new solid electrolyte batteries being developed by Goodenough and his team. (Search "Glass Battery" on web).
     
  5. Apr 18, 2017 #4
    Pardon my mistake. It was a typo error. Actually I was asking regarding the type of generator I should buy for charging 12V 7amp. I am going to connect three blades which are to be used as wind turbine blades. The generator should generate electricity when the blades are rotated.
     
  6. Apr 18, 2017 #5

    sophiecentaur

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    For a static or boating application, I would think a lead acid battery would be best value. You should use a regulator, of course, with some basic speed limiting by short circuit braking. It's debatable and site specific whether you need a sophisticated boost converter to drag a few Coulombs out of the generator when the speed is too low to provide a 'natural' charging voltage. A short burst of stiff breeze can do the work of hours of 'joule thieving' and it's just another thing to go wrong.
    What do you mean by that? Do you already have a generator (Alternator)? What is its design rotation speed and will your blades be matched to that? The pitch and length of the blades will be fairly critical if your total supply of charge (Ah) is marginal for your requirements. Small turbines often have multiple blades.
     
  7. Apr 18, 2017 #6

    davenn

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    what sort of battery is it ? sealed lead-acid ? something else as charging methods will vary depending on battery type

    if a lead-acid type, then just use an alternator designed for a car
     
  8. Apr 18, 2017 #7

    russ_watters

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    The generator should be matched to the turbine. So first you need to determine how much rotational power your turbine can generate to spin a generator.
     
  9. Apr 19, 2017 #8

    sophiecentaur

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    It strikes (from your comments) me that you don't seem to have a lot of technical knowhow in this field. Wind turbine design is difficult and, unless you live on top of a windy hill, you will need to get things just right if you want this system to work. You would be well advised to buy a commercial unit unless you are just doing this for fun. Turbines, alternators, charge controllers and batteries are all specialist items. If they are not all matched to each other, you can get very poor (or disastrous) performance.
     
  10. Apr 19, 2017 #9

    sophiecentaur

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    I suspect that there are a lot of garages and sheds around, with bits of Wind Energy projects that never delivered the goods because they were approached with more optimism than knowhow. That will also apply to the projects that have been sold by an over enthusiastic salesman.
    It's so dependent on the actual conditions. For instance, you'd think that a wind generator would be just what you want on a Yacht in a good breeze. True - except when your course involves days of running in a high performance yacht with the wind behind you and the turbine has only a few knots of wind to work with for all that time.
     
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