Battery Charging using Energy Harvesting

[savvej]

Hi All,

If small amounts of power is being generated from multiple identical sources, how is it possible to accumulate it (add up) to generate greater power?
say 1uW is being generated at 1V , 1uA. And it is intermittent.(Say a vibrational or piezo source)
I want it to charge for example a 1.5V 500mAh standard rechargeable battery with this source.
I don't mind whether it takes 3-4 days for my battery to get charged.
What is the intermediate circuit required(is it possible to have one)?

Regards,
SAV

 

[Nigel Goodwin]

First off do the maths - and work out how many intermittent 1uW you would need to charge the battery

 

[savvej]

So energy stored in a battery = 1.5*500*3600*10^-3=E=2700 joules=2.7KJ
Energy per intermittent process = 1uW
So that evaluates to ~27*10^8 ~2.7 billion intermittent shocks !!!
Say freq of shocks is 1KHz => then it will take around a month to charge.. Hmm this is considering no loss . Well such a small source might not be worth then..
Any thoughts??

Are you aware of the power output of a potato battery with zince and copper plates?

 

[audioguru]

I betcha a nail in a wooden deck continuously, not intermittently picks up more than 1uA from local radio stations.
I betcha my tie clip continuously, not intermittently picks up more than 1uA from mains hum.

My very cheap Chinese solar garden lights glow all night every night.

1uA is almost nothing. How can anybody harvest nothing?

 

[NorthGuy]

In the old times there were self-powering watches which were winding up a spring when you move around with them on the wrist. I bet this mechanism could be used to charge batteries.

 

[audioguru]

A watch uses a very low amount of power so the old spring and moving weight mechanism provided a very low amount of power.
Then why use a rechargeable battery charged with extremely low current that might take weeks to charge?

A hearing aid uses low power but does not use a rechargeable battery. Maybe the hearing aid can be powered from a very low power piezo generator so when the deaf person needs to hear something then he simply taps his foot with the piezo in his shoe.