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Wind powered battery charger Answered

HI.. this is my first post on these forums. I want to build a small windmill that will charge ordinary rechargeable AA sized batteries. however there's a problem. I have hooked up my windmill to a motor which produces DC current. Now, the motor provides enough and MORE current to charge the batteries. My problem is how do i protect the battery from overly high voltages and currents that may be generated by the motor?

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racingmouse (author)2009-05-06

Hey! Interesting debate - I wish I could build a wind powered battery charger myself but I think I am too left handed. I have searched the internet but cannot find anywhere where it is possible to purchase such a charger. Do you know somewhere? I will have to install it in my Rickshaw bicycle so it can provide electricity to a portable Ipod speaker system running on 4 big AAA batteries. Hope for some comments :)

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jimbo13 (author)racingmouse2009-07-07

i am building and selling wind battery chargers on ebay, they charge 2 AA and 4 AA batteries, they have no problem with overcharging. go to ebay and enter keywords wind battery charger AA .

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crnwoodnut (author)2009-05-26

This is a work in progress and i am wondering if i can get some advice on chargeing a 12v battery to turn a wood lathe . When i bench teasted the motor with a 18 volt battery drill I actually got 18.48 voltsmore tha enough to chareg a battery right? But what happens is the battery becomes dead dead it was not charged to start with it 5.95 volts in it. but now nothing.

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crnwoodnut (author)2009-05-26

blocking diode and recirtifers whats the differance

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forgesmith (author)2008-07-12

Controlling the current is very important, rechargeables can get quite hot if charged too fast and even "acceptable" fast charging (about 15 min to 1 hr) will shorten their life. What I'm reading on searches is 100mA is about right for AA size.

So first you control current. Here is a basic circuit called a current mirror, just two transistors and a resistor, and math. Here is a basic current source using a Zener diode, less math (but I think the one below it with the LED looks cuter).

Controlling voltage is less important than current, and it's common to charge batteries at a (slightly) higher voltage than what they are. Rechargeable cells are under 1.5V, closer to 1.2-1.3V, a simple 3V Zener diode will work for 2 cells.

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mahela007 (author)forgesmith2008-07-12

thanks. I'll check those two out

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killerjackalope (author)2008-07-09

Voltage regulator, you'd have to be making a fair bit of current to damage them unless it was constantly high, so maybe a constant current voltage regulator...

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user

can i make a voltage regulator? i saw some on the net.. they seem very ard to build. Are there more simple versions?

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LinuxH4x0r (author)mahela0072008-07-10

Yes and no. Sure you could make something with resistors, but the actual regulator is impossible. Try this for 2 in series or this for parallel

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He could get a few free chips...

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LinuxH4x0r (author)2008-07-10

What is the voltage/ current? You would only need a resistor to limit it, or just closely monitor your batteries (take readings with a meter every half hour). If you have 12vdc I'd suggest getting a jump starter pack and charging that and using it's cigarette lighter plugs to power a regular charger.

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