Need help in realizing a wind powered mobile charger.

Thread Starter

arun the curious

Joined Aug 6, 2012
60
Project is a Wind powered mobile charger.
Here wind energy is converted to dc power using dc fan(processor fan)
12 V,0.25A rating.
I use 3 fans in series as i dont get enough wind...which together generates close to 4V and current greater than 200 mA.
I use a voltage regulator ckt using 7805 IC and capacitors at the fans output terminal.
The charging req of typical battery is 3.7 V;200mA.

But when i connect my phone to this...earlier it used to charge but now sometimes the phone detects it and never charges.
 

wayneh

Joined Sep 9, 2010
16,114
The regulator drops voltage - it cannot boost - so the output voltage is likely well under the expected 5V.

Many phones also require a specific voltage to appear on the USB data pins in order to charge correctly.
 

wayneh

Joined Sep 9, 2010
16,114
Please define the charging requirements of the phone. Is that the 3.7V and 200mA?

Eliminating the regulator should be your priority, since it is wasting most of your power. Search for a DC-DC converter that can tolerate your input conditions and will output what you need.

On the output of the generator, I'd be tempted to add a peak detector, which is just a blocking diode followed by a large capacitor. This will dramatically smooth out the power seen by your DC-DC converter. Maybe these things don't need it, but it seems like a good idea except for the loss across the diode.
 

Thread Starter

arun the curious

Joined Aug 6, 2012
60
Thanks wayneh...
yes,it is 3.7 v;200mA battery.

so is it how u recommend...?

fan---> dc-dc converter--->peak detector--->charger pin output.
 

Thread Starter

arun the curious

Joined Aug 6, 2012
60
Also... i get current in excess of 200 mA...MM reading goes to 1 when measuring current set to 200 mA range.
How to limit current without dropping much voltage?
 

wayneh

Joined Sep 9, 2010
16,114
My notion was to use the peak detector immediately after the generator, to feed smoother DC to the converter. I don't know for sure it needs that, but it's something to consider as you shop for a converter.

You generator may be able to drive more than 200mA through your meter, but that doesn't mean it will drive that into a battery. Current limiting - if it is needed at all - might be something the DC-DC converter will provide.

Are you charging the battery outside the phone? You may need a charge controller to avoid overcharging. If it's in the phone, the phone is likely handling the charging process.
 
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