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I found this discussion while looking for a way to wirelessly charge my 3S drone battery. I would like to find a way to drop my drone on my desk (like I do my phone) and let it charge.

If I am understanding the discussion, in order to safely use a wireless qi receiver and transmitter I would need a lipo charger configured as: I apologize in advance for my rough illustration, I am far outside of my sandbox here.

I am wondering if my 3S 11.1V battery would charge in the above scenario since each cell in the series is 3.7V?

Adafruit uses what seems to be 3 x 2200mAh balanced batteries at 3.7V in their example with the lipo charger. The 3S drone battery I use is a 3 cell lipo in series at 3.7V each totaling 11.1V. Could I charge my 3S in the scenario above? Or since the total 3S is 11.1V does that disqualify this battery as the maximum this lipo charger will charge is 3.7V total?

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  • \$\begingroup\$ You could but it would be faster to plug it in and get more power than Qi. To achieve high performance requires EMI skills and WPT skills \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Aug 18 '20 at 18:15
  • \$\begingroup\$ The antennas and circuitry involved would likely weigh more than your charging connector. \$\endgroup\$ – Cristobol Polychronopolis Aug 18 '20 at 18:19
  • \$\begingroup\$ @TonyStewartSunnyskyguyEE75 and CristobbolPolychronopolis thank you. I do realize boredom is in control of my sanity these days... But you can confirm that in theory my scenario above would work on a 3S battery? \$\endgroup\$ – Chris Aug 18 '20 at 18:47
  • \$\begingroup\$ My clients transfer WPT to 20 LEDs or 750mW with a smallish flat 8cm ferrite rod coil that works well using the license free RF channel for industrial use. you possible want >4A instead of 50mA using a resonant coil with ferrite tuned with C1% \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Aug 18 '20 at 18:58
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    \$\begingroup\$ This is not a practical idea, and even the basic non-wireless parts of your scheme are wrong, for example the charging board you propose to use is utterly and dangerously unsuitable for a 3S pack. First you need to learn about battery systems, then maybe you can consider some sort of spring-contact charging system giving DC supply to a proper charger. \$\endgroup\$ – Chris Stratton Aug 18 '20 at 20:12
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how about kick it up a notch and design your coil rectifier to work using the “bottle feed” setting of a cheap $60 induction desktop cooker.

Make it look like a Space X launch /landing Pad.

enter image description here

sniff the resonant frequency and tune with plastic caps

but don’t try 1800W until you got a bigger drone.

But ensure to absorb all the radiation so your motors don’t melt.

  • add a large diameter coil 10cm below your old landing feet with a new tripod holder for your New heavy gauge coil with resonant cap to match impedances using Falstad’s RLC simulation bode plot.
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  • \$\begingroup\$ I will probably read this 10x more and it will continue to blow my mind... Incredible. Thank you for your time and expertise Tony... From what I'm hearing from Bruce Abbot and Chris Stratton the scenario image above is dangerous and would not work. I would love a sliver of your knowledge to get my pet project working. This cooker idea is crazy cool! \$\endgroup\$ – Chris Aug 18 '20 at 21:32
  • \$\begingroup\$ It’s safe with an auto load shutoff for all except baby bottle warmer which are plastic or glass. Then I think there is no detection. Just low power for ?40kHz? perhaps just right for high charger power. It can be tuned to what you need with science. The losses are inverse squared with gap BUT you need the smart CC CV charge controller on board. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Aug 18 '20 at 21:35
  • \$\begingroup\$ Or you could watch the voltage and current with a 50mV current sensor full scale on gnd side before you go further and learn how to automate it. But of course you know these can bust if you overcharge and make everyone nervous as you shovel it in the dirt and then learn about contaminated soils. And MSDS on explosive fires. But if smart you can manage it. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Aug 18 '20 at 21:55
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Or since the total 3S is 11.1V does that disqualify this battery as the maximum this lipo charger will charge is 3.7V total?

Your battery has three 3.7 V cells in series. Your charger can do one 3.7 V cell. So one charger won't do it. But 3 chargers would (with appropriate cable between them and the battery). So you 'just' need 3 wireless charging transmitters, 3 wireless charging receivers, and 3 single cell lipo chargers.

But you still need to plug the drone battery into the charger, so what's the point?

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  • \$\begingroup\$ Thank you for looking at this for me. \$\endgroup\$ – Chris Aug 18 '20 at 21:33

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