Author Options:

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?


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 :)

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 .

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.

blocking diode and recirtifers whats the differance

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.

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...

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

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

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.