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Low Amperage battery charging.

MadMechanic

Aug 28, 2012
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Aug 28, 2012
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Hello All,

I have a general question about battery charging. I am messing around with small scale power generation (as some of you may have seen in previous threads) and I have a question about battery charging.

Originally I was aiming to generate enough power to charge any USB device with only my generator. USB standard power is 5V, 1A. So far I have had success charging a cell phone at 5V 300mA with no problem. I have tried larger loads, but it seems my generator is maxing out around 350mA when I increase rpm. I have not yet tried my ipod touch which should draw anywhere from 500mA to 1A.

I have plenty of voltage out of this.... easily in excess of 50V at low rpm, but the amperage seems limited, even though the motor I am using in reverse as a generator is rated at 1.7A.

The question is If I were to add a 12V rechargeable battery to the system as the primary phone charging source, could I (trickle-charge) the battery from the generator? Being that the generator's amperage is lower than the load on the battery....would the battery recharge at 350mA when not loaded?

Would I be safe to assume that as long as the battery has (non-loaded) resistance lower than the pull of 350mA that as long as my voltages were even or greater the battery would slowly recharge? Thanks,
 

davenn

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Sep 5, 2009
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Is that 50V or so an open circuit voltage or one with a load

the curent will probably, mainly, be limited by the thickness of the wire used in the windings

Dave
 

MadMechanic

Aug 28, 2012
48
Joined
Aug 28, 2012
Messages
48
Is that 50V or so an open circuit voltage or one with a load

the curent will probably, mainly, be limited by the thickness of the wire used in the windings

Dave

50V is the open reading across the meter. I got it up to 35V by twisting the shaft with my fingers believe it or not. Im using a stepper motor wired in Bipolar parallel with 4 sets of leads across 2 separate full bridge rectifiers in series with two 4700uF capacitors. I seem to get more voltage and less amperage with the motor in Bipolar series orientation.

Should I possibly try to find a motor with a larger winding gauge? I would love to get 1A total out of one of these after rectification.
 

davenn

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Sep 5, 2009
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yeah that would be an idea :)
stepper motors would be very inefficient for power generation

Dave
 
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