Interesting thought.

Discussion in 'General Electronics Chat' started by ConstructionK88, Sep 14, 2018 at 11:58 PM.

  1. ConstructionK88

    Thread Starter Member

    Jul 25, 2018
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    Suppose I need a simple circuit that did this:
    1- when power flowed from a windmill genrator the power was used to charge a battery.
    2- when the windmill stopped producing power the battery begun supplying power to the load and cut the windmill out of the demand until the battery died.
    3- battery power full then windmill power not accepted. Battery depleted windmill power accepted.
    4-the windmill doesn't supply power to the load. Only charges the battery when there is no demand to the load. When the load is required the windmill's power isn't accepted by the battery. Only the battery supplies power to the load.

    Want to see how long the wind can keep a battery charged to power a small led without any external charging.
     
  2. Ramussons

    Well-Known Member

    May 3, 2013
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    Lets make your requirements easier to understand - as I understand :D

    No connection between Windmill and Load.

    1) Charge the Battery Fully from Windmill
    2) Disconnect Windmill
    3) Discharge the Battery Full thru' load.
    4) Disconnect Load
    5) Go to Step 1
    ... and so on..
    o_Oo_Oo_O
     
  3. ConstructionK88

    Thread Starter Member

    Jul 25, 2018
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    Exacta! A quasi digital setup using low and medium power transistors strictly for switching on or off between the 3. The goal isn't to keep the load constantly powered but only powered when the battery can supply the demand after charging.
     
  4. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    LH Battery Manage. 00000.jpg There are battery management ICs but it would be helpful to have specs. on battery & windmill to choose
    one. I'll throw in a discrete component solar battery monitoring circuit to show how messy it can be. It was to charge 2 LI-PO4 18500 3.2 batteries on series. Add a battery condition signal output to an OR gate, other input is a load demand signal , output = connect load to battery.
     
  5. wayneh

    Expert

    Sep 9, 2010
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    Just some thoughts.
    Are you sure you don't want the windmill to power the load? For instance suppose the windmill is cranking plenty of juice and could power the load and charge the battery (which is say, only half charged at the moment) at the same time with capacity left over. Do you want it to turn off the load until the battery is fully charged?
    I'm just asking because a typical off-the-shelf solar charge controller can power the load and the charge the battery simultaneously. The behavior you've described is not the typical arrangement.

    That has nothing to do with the windmill and everything to do with the capacity of the battery. The battery doesn't care or remember what primary source was used to charge it.
     
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  6. ConstructionK88

    Thread Starter Member

    Jul 25, 2018
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    Wow. Does it need to be so complex??
     
  7. ConstructionK88

    Thread Starter Member

    Jul 25, 2018
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    This is hypothetical? Forgive me for the misdirection but it's a special project. Something I've been thinking on for like 15 years. I've just now got the means to build it.
     
  8. wayneh

    Expert

    Sep 9, 2010
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    I'm not sure that answers the question. I'm essentially asking why you can't use an off-the-shelf load controller. They're purpose-built for this task and use modern ICs designed specifically for this application. It's great if you simply want to roll your own or need something that's unavailable on the market. But if you're good with following the same general logic as these devices the project will be simpler and we won't need 20 posts back and forth as folks here try to tease out the specifications you want to achieve. Comparing and contrasting to a commercial device would tell folks here what you're up to.
     
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  9. ConstructionK88

    Thread Starter Member

    Jul 25, 2018
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    Well forgive me please and I sincerely mean that. I can't exactly let the cat out the bag on this because it is my idea and I know it's application but to tell it all means I lose it all. However if it works I'd gladly $how my appreciation to anyone that help$. I apologize but no I don't think any modern circuit would work and my posted analogy is a bastardized version of the end product. Im just looking for a simple on/off circuit that would work in this way. Its quite ok if its not possible but this is why i joined AAC. It's a dream in progress that's been eating at my brain for 15 years....
     
  10. ConstructionK88

    Thread Starter Member

    Jul 25, 2018
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    Yikes I think I see mosfet's in there. Awesome response but I was hoping for something simple.
     
  11. ConstructionK88

    Thread Starter Member

    Jul 25, 2018
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    My apologies but load, windmill, and battery are all in hypothetical "?". What I'm up to is proprietary? I believe that's the correct word. Invention is more accurate. But hey any help that makes it work with this hypothetical circuit will be repayed in kind.
     
  12. MisterBill2

    Well-Known Member

    Jan 23, 2018
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    While using only the battery to power the load and never powering the load from the windmill is an interesting choice, it will certainly result in both a much shorter battery life and a lot less power to the load. So there must be more to this tale than is revealed. Just like many other postings with questions, not providing enough information usually results in answers that are based on not knowing just what is actually required.
     
  13. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    To the OP, our clairvoyant modes are disabled.
     
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  14. wayneh

    Expert

    Sep 9, 2010
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    OK, so the load is always to be disabled so that battery charging occurs when the wind is blowing.
    What if the battery is only, say, 30% charged and the wind stops for 5 minutes. Do you really want to shut off any additional charging until the load has fully depleted the battery? Suppose the wind picked up again a few minutes later and could now be charging the battery.
    You'll need to define "depleted" in terms of percent State Of Charge. Depending on your battery chemistry it can be challenging to estimate SOC. It's easy with lead-acid but very tough with Li-ion.
    That could be accomplished with a simple switch. The battery has only two states; taking power from the mill or providing power to the LED.

    Your challenge is defining the conditions that will cause that switch to flip from one state to the other. Your instantaneous inputs are battery SOC, current wind conditions, and perhaps whether the load is needed or not (such as a daylight switch on an LED). You seem to also be imposing a "history" input, meaning that once a condition is triggered, you want to stay latched in the chosen mode no matter what the instantaneous inputs are.

    Designing the electronics to achieve your desired logic will be "easy". You can take that for granted. But no one will want to even start on it when the logic is undefined. You need to go through methodically and consider all possible combinations of inputs and operating modes.
     
    Last edited: Sep 16, 2018 at 11:15 AM
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  15. ConstructionK88

    Thread Starter Member

    Jul 25, 2018
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    It's actually kind of difficult to explain. Having someone's name on the tip of your tongue and know thier face but can't ever get it out situation here. That's why I said hypothetical because I can't cement the idea to just one thought. Can I assume it is possible for a simple circuit to essentially turn off its input the turn on it's output when power inside the circuit is enough to power the load. Like charging a cellphone but certainly not as complex and with direct electromechanical charging.
     
  16. ConstructionK88

    Thread Starter Member

    Jul 25, 2018
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    Supposing a fast, near instantaneous charging battery I have. It would also discharge quickly but not instantly. A capacitor. I got this idea from seeing various circuit's losing power and the led indicator's or other loads running for a brief but curiously impressive amount of time. Even my tda2050 circuit will play for approximately 2-3seconds after the battery is disconnected. It gave me an idea that I doubt is possible but be damned I'm not going to try.
     
  17. MisterBill2

    Well-Known Member

    Jan 23, 2018
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    For a simple circuit to disconnect the load whenever the battery is charging, just use a normally closed reed switch with a current coil around it to disconnect the load whenever the wind turbine is delivering enough voltage to force a charging current into the battery, and have a diode in series with the generator to prevent the generator from drawing down the battery. That meets all of the requirements except waiting until the battery is fully discharged. And it is simple, having only three electrical parts.
     
  18. whitehaired novice

    Member

    Jul 15, 2017
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    I think you are noticing the effect of a capacitor's time constant. When charged from a battery with a low internal resistance the cap charges quickly--apparently instantaneously. When discharged through a fairly high resistance such as your amp it discharges more slowly. But the charging power and the discharging power are the same--there is no net power gain.
     
  19. MisterBill2

    Well-Known Member

    Jan 23, 2018
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    Of course, there is no power created, there is power lost as it flows through internal resistances, though. I don't see how that relates to my post,(#18), though. Time constant is always present, but sometimes the times are so short that they don't matter in some situations. "Instant" is usually understood as faster than the observing tool is able to observe.
     
  20. WBahn

    Moderator

    Mar 31, 2012
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    The powers can be MUCH different and, in the case you are describing here, the charging power is MUCH higher than the discharging power. But remember that there is no such thing as is conservation of power (between charge and discharge) -- but there IS such a thing as conservation of energy.

    If you use a fixed voltage source to charge a capacitor from fully discharged to the source's terminal voltage, the total energy delivered by the source will be twice the energy stored on the capacitor -- the remainder will be lost in the internal resistance of the source, capacitor, and interconnects, no matter how small they may be. If the charging time is very small, the power will be quite high since the average power is the energy transferred divided by the time taken to do so. The average power delivered by the source will be twice that absorbed by the capacitor. Similar -- but more complicated -- issues apply if the capacitor is replaced by a battery. If the terminal voltages of the two are not equal, then the current flowing between the two will dissipate energy as heat as it crosses the differential.

    As the capacitor is later discharged to provide energy to some load (amp, LED, whatever) over a longer period of time, the total energy provided cannot exceed the energy that was stored on the capacitor (which is only half the energy provided by the original source) but, because it is being transferred over a longer period of time the average power is considerably less and the ratio of the two can easily be many orders of magnitude.
     
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