# Piezoelectric Discs As Batteries

Discussion in 'General Electronics Chat' started by WindTapper, Feb 3, 2012.

## Do you have any experience with piezoelectric devices?

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1. ### WindTapper Thread Starter New Member

Feb 3, 2012
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I am trying to design an alternator that works off wind power and that people could build themselves. I have a device that turns in the wind with little resistance and can turn a light weight magnet rotor. Setting the coils around the outside circumference, with 70 neodymium magnets rotating past them, I still wish to reduce the cost of the coils.

The idea I am trying to develop generates a question about parallel voltage sources. Piezoelectric discs supposedly give 10 volts with 0.001 amps. I can not find a formula for voltage sources in parallel. I read the thread about two batteries in parallel, but the piezoelectric discs have 10,000 ohms each, which should reduce the spark referred to.

Is there data or a formula anywhere on parallel voltages? My idea is to put several piezoelectric discs in parallel with each other and with a coil that is generating, say, 4 volts. What do you think would happen? Or should I just build it and then see what happens?

I actually need to get 14 volts in order to charge a 12 volt deep cycle battery. And I will have to use a rectifier, which will essentially cut my output in half at least. I assume that with so much resistance in the piezoelectric discs that I will not be able to connect them in series to get to 20 volts....

I would be much obliged if anyone would care to comment on this project!

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2. ### WindTapper Thread Starter New Member

Feb 3, 2012
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What about putting a piezoelectric disc in parallel with each coil? I plan 14 coils with 14 columns of 5 neodymium magnet discs. I guess that could produce too much voltage. Maybe three piezoelectric discs on three coils, since I would only get less than half the voltage after rectification?

3. ### Audioguru New Member

Dec 20, 2007
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Nobody makes a piezo disc that is large enough to produce a couple of mA. You need many AMPs to charge a big battery so forget about using piezo discs unless you use thousands of them that are all vibrating at the same time.

I have seen a little windmill on boats that charges its little battery all day long. The little battery is used for a few low power lights.

Some people use a pretty big windmill to charge a pretty big battery.

4. ### WindTapper Thread Starter New Member

Feb 3, 2012
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Please consider an experimental circuit: An expanded alternator where you have access to individual armature coils, set up to charge a 12-volt battery through a bridge rectifier with extra -- for safety's sake -- diodes protecting the circuit and battery from AC and battery discharges from leaking in the opposite direction, because we are converting AC to DC.

On a "Two Battery" thread here at the forum we have a proposed circuit of two batteries linked in parallel. Response: A 10-volt will charge a 5-volt battery with sparks. The response involved a question of the interior resistance of the batteries as providing a reason for the sparks. Lack of much resistance lets lots of amps flow, in other words.

With piezoelectric devices you have much resistance. So, my question is, "Couldn't I add volts to one of the armature coils by attaching a piezoelectric device -- and activating-controlling it to produce the proper valence -- in parallel to that one coil?"

The amps go through the coil, while extra volts come from the piezoelectric disc. The amps do not go through the piezoelectric device because it has so many ohms. Can I not increase the amps and volts, therefore, in the armature coil, which would be in series with the rest of the armature, so adding volts and amps to the whole armature circuit?

Last edited: Feb 5, 2012
5. ### Audioguru New Member

Dec 20, 2007
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A piezo produces an extremely low current. If it feeds an extremely high resistance then it produces some voltage. A battery or an alternator is not an extremely high resistance, instead they are extremely low resistances so a piezo or even thousands of piezos will not do anything.

A guy put piezos in his shoes. He walked all day long and the resulting rectified electricity barely charged the battery in his ipod.

6. ### WindTapper Thread Starter New Member

Feb 3, 2012
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Thanks Audioguru for straightening me out on this. I was separating the volts from the amps when I should have remembered the water pressure analogy for volts. I can not move a liter of water using a milliliter of water, no matter how much force the milliliter of water has on it.

You have saved me much time. Thanks again.