A very simple Li-Ion battery charger from China. It contains a very simple 2-transistor switching power supply and a voltage regulation with just a Zener diode. There's also an indication circuitry to indicate charging / fully charged using a red / green LED. This is done using only a 3-pin LED and resistors, without any active components. This power supply has no fuse and a questionable mains separation, so it may be dangerous The output voltage is very poorly regulated and in this case it was 4.45V, enough to make a Li-Ion battery catch fire or explode.<br /><br />You can support me on Patreon:<br /><a href="https://www.patreon.com/DiodeGoneWild" target="_blank" rel="nofollow">https://www.patreon.com/DiodeGoneWild</a><br />...<br /><a href="https://www.youtube.com/watch?v=CeUTXruMxD4" target="_blank" rel="nofollow">https://www.youtube.com/watch?v=CeUTXruMxD4</a>