I can't find my battery charger. So I am using the fan and other ways to test out the batteries until I find it or get a new charger. The 5V coming in had to be Stepped down to 4.2V which may mean there was slightly higher current filling the batteries. But, there is also some power loss by the charging circuit so I suspect it about equalizes. Li ion batteries should never be discharged below 2.5V or used if they ever have been below 2.5V. They should never be charged above 4.2V. Likely damaged if they are ever charged to 4.3V. Never charge a frozen li ion battery. Check how much current they can handle also and do not exceed that. Make sure to learn as much as you can about li ion batteries before you use them. Read the seller's specifications for the batteries and read the reviews to see if there are complaints about the seller's accuracy of specifications of anything you buy. There are many fake li ion batteries and sellers that lie about the specifications of the li ion batteries they sell. These EBL 18650 batteries cost about $3.50 each on Amazon. https://www.amazon.com/shop/electronzapdotcom for links to where I bought most of the things I use in my videos. Electronzap earns money from this storefront. https://www.patreon.com/electronzap If you'd like to support my efforts directly ... https://www.youtube.com/watch?v=mRSSoeS2WBo

https://www.youtube.com/c/electronzap https://www.patreon.com/electronzap https://electronzap.com/ https://www.reddit.com/r/ElectronicsStudy/ https://www.instagram.com/electronzap/ https://www.amazon.com/shop/electronzapdotcom As an Amazon Associate I earn from qualifying purchases. Americans should check out that link! No extra cost to you! Another use for the LM358 non inverting comparator circuit can be to turn a buzzer on when light levels get low enough. Not sure how well the LM358 output can power a buzzer, I used the output high signal to turn on a NPN bipolar junction transistor (BJT) wired as a switch in series with the buzzer. #electronics #LEDs #buzzer ... https://www.youtube.com/watch?v=66Ps8yAcVZ0

List of my videos https://www.youtube.com/c/electronzap/videos https://www.youtube.com/@Electronzap/community for most of the diagrams I've used in my videos. https://www.amazon.com/shop/electronzapdotcom/list/1ADLVE33FFFYL?ref_=aip_sf_list_spv_ofs_mixed_d As an Amazon Associate I earn from qualifying purchases. Americans should check out one or more of those links before making any purchases. There's no extra cost to you. https://www.patreon.com/electronzap https://electronzap.com/ https://www.reddit.com/r/ElectronicsStudy/ #Electronics #Howto #diy ... https://www.youtube.com/watch?v=M28Zlki8WVY

https://electronzap.com/brief-pnp-switch-circuit-that-turns-on-with-a-high-input-voltage-thanks-to-npn-bjt/ https://electronzap.com/brief-circuit-schematics-with-short-video-list-of-pages/ https://www.youtube.com/c/electronzap https://www.patreon.com/electronzap https://www.reddit.com/r/ElectronicsStudy/ https://www.instagram.com/electronzap/ https://www.amazon.com/shop/electronzapdotcom As an Amazon Associate I earn from qualifying purchases. Americans should check out that link! No extra cost to you! PNP bipolar junction transistors BJT switches are nice because they are on the high side of the load, but are awkward because you need to connect to ground to turn them on. Instead you can use a switch to provide a high signal to a NPN BJT, which connects the PNP base to ground. Thus turning on a PNP BJT switch load , with a high input signal. #BJTs #electronics #switch ... https://www.youtube.com/watch?v=wcYt8gwz1ow