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AC micro-charging a LiPo Battery
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Please be positive and constructive with your questions and comments.

AC micro-charging a LiPo Battery

by jkanalakis on Tue Aug 04, 2020 8:08 pm

I would like to charge a small LiPo battery using a small 1v and about 0.1µA AC power source, like a small windmill. Is there an Adafruit component that has the bridge rectifier to convert AC to DC and then channel it through something like a Micro-Lipo charger (https://www.adafruit.com/product/1904)? Any sort of direction would be greatly appreciated.

Thank you.

jkanalakis
 
Posts: 10
Joined: Sun Oct 22, 2017 6:08 pm

Re: AC micro-charging a LiPo Battery

by adafruit_support_bill on Tue Aug 04, 2020 8:38 pm

1v would be a problem, since the low-voltage cutoff for a LiPo cell is in the 3v range. You typically need at least 4.5v input to the charge controller.

Since you are starting with AC, you could consider a voltage multiplier circuit: https://en.wikipedia.org/wiki/Voltage_multiplier But the forward voltage drops of the diodes would consume a good chunk of your input voltage.

The 0.1µA would also be an issue. That is pretty low to start with and any voltage boost is going to come with a proportional drop in current - not to mention losses because the conversion process is never 100% efficient.

I don't think you would get much useful charge current output unless you can find a generator with a bit more capacity to start with.

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Re: AC micro-charging a LiPo Battery

by jkanalakis on Wed Aug 05, 2020 6:36 pm

Thank you for the extremely helpful reply. Based on your tips, I’m going to try to connect a few small windmills together in parallel. Each windmill will connect to a bridge rectifier to strip out the negative AC voltage and then connect each rectifier’s positive output to a diode. All of the diodes are then connected together in parallel to a large capacitor as you suggested. Perhaps from there I can flow more current and voltage into the LiPo charger. So essentially the change would be to add multiple low-voltage/low-current sources. It will probably take a lot of these small windmills to power a small microcontroller. Thank you very much for the help!

jkanalakis
 
Posts: 10
Joined: Sun Oct 22, 2017 6:08 pm

Re: AC micro-charging a LiPo Battery

by adafruit_support_bill on Thu Aug 06, 2020 5:44 am

Pay attention to the forward voltage on your rectifiers. All diodes have a forward voltage drop which can be as much as a volt or more. Schottky diodes tend to have a lower voltage drop than other diode types.

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Please be positive and constructive with your questions and comments.