This was a happy accient. I was charging a drone battery though an adapter with overvoltage protection, which started beeping and increasing in frequency as the battery got close to full charge. There is a good bit of sound at the end, when i pulled off the battery and the capacitors in the charger discharged. :). Have fun with it! if you want, let me know what you did with it. Cheers!. Recorded on zoom f1 with xyh-5.
Author: Imafoley