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For a home robotics project I want to fly a kite using a computer. For this to happen I need an electro motor up in the air (attached to the kite) which obviously needs a battery up there as well. From some smart people I understand that using a LiPo battery would be the best for this (because of the high energy to weight ratio). I also understand however, that a LiPo battery needs a special charger. My end goal is to charge this battery in the air by also hanging a small wind-generator under the kite so that the kite can fly indefinitely. If the battery cannot be charged while it is being used I can of course use two batteries, charging one while the other one is used.

So let's say I've got a 11.1V LiPo battery which uses about 500mA to 1A for the motor.

My question: is it possible to charge this battery from a wind generator, and if so, what hardware (preferably very low-budget) would I need for this to happen?

All tips are welcome!

[EDIT] Wow! I am overwelmed by the amount of in depth answers. I am a bit lost in them as well though, and I think I am after a bit more of a "beginners answer". As far as I understand, a wind generator supplies AC power in varying amount of Volts and Amps (right?), which needs to be converted to DC power with a constant amount of Amps (right?). So I guess that would mean I need the following order: Wind generator => Rectifier => Li-Polymer Battery Charge Management Controller (like e.g. this one) => LiPo battery pack.

Is this correct?

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    \$\begingroup\$ Electric motor in the air and attached to the kite. For my benefit, can you explain why or link me to the question that resolved this. \$\endgroup\$ – Andy aka Mar 29 '13 at 13:48
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    \$\begingroup\$ Here is the best link I could find on SE on charging LiPo:electronics.stackexchange.com/a/25405/15779 \$\endgroup\$ – Bobbi Bennett Mar 29 '13 at 15:29
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    \$\begingroup\$ How much weight can your kite lift? \$\endgroup\$ – Bobbi Bennett Mar 29 '13 at 17:47
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    \$\begingroup\$ "I need the following order: Wind generator => Rectifier => Li-Polymer Battery Charge Management Controller => LiPo battery pack." - That's correct. Finding an appropriate charge controller seems a little difficult because of the varying nature of the power supply, so you may want/have to come up with something 'homebrewed'. \$\endgroup\$ – JimmyB Mar 29 '13 at 18:04
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    \$\begingroup\$ Lead-acid batteries would probably make things easier - if one has some kg of lift to spare ;-) - Yet I think that LiPo isn't any more complicated to handle than those: Limit the charging current and voltage (voltage regulator + resistor for the simplest case, plus a diode maybe) and you're ready to go. Not very efficient of course, but extremely simple to build and resistant to varying supply power. \$\endgroup\$ – JimmyB Mar 30 '13 at 12:22

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