# Capacitive discharge excess being used for battery recharging

I am currently designing a circuit similar to a cattle prod that is intended to be attached to a drone. The cattle prod is powered by a lithium-ion battery, charging up a capacitor and then quickly discharging through a material. It will be delivering approximately 1 J of energy with a 10 kV voltage, at about 7 kHz. I am trying to make the system more efficient.

I know next to nothing about power electronics or batteries (I am studying computer science), and was wondering if it is possible to use any residual current from the discharge to cycle back through and recharge the battery without any mechanical components? If not, can you please explain why? I am currently looking at the MAX8900 IC, and if it is possible I would like to know what I would have to do to process the current so it could be the input to such an IC.

• Placing a cattle prod, also known as a shock prod, onto a drone... Why would you possibly want to do this? Shock your friends? Shock birds? – Harry Svensson Oct 10 '18 at 10:51
• Since a capacitor would be used for the discharges, you will by default recover the leftover energy: if e.g. 5 kV remains in the cap after each discharge, when recharging it for the next pulse you'll only have to recharge it from 5 kV to 10 kV. You do realize that 1 J discharges at 7 kHz require 7 kW of power, which is impractical for a "drone" (assuming a 1 kg quadcopter)? – jms Oct 10 '18 at 11:01
• @HarrySvensson it is a forestry project haha, I'm not that sadistic! Although now I am getting ideas... – eles Oct 10 '18 at 11:16
• @jms thanks! As for the second part of your comment, are you able to explain? Is it not dependent on the time constant of my circuit? – eles Oct 10 '18 at 11:16
• You may have some leeway depending on where you live, but be aware that it is possible that what you intend to build is very illegal. Aside from that, a great deal of skill is necessary to deliver a "safe" shock of any consequence. Also I'm pretty sure that as jms indicates 7000 1 joule pulses per second will not particularly resemble safe. – K H Oct 10 '18 at 20:57