A Dying Lithium-Ion Battery

Well, I’ve come across another dying battery.  This time though it’s not brand new… however, it’s not that old either. This is a Samsung 30Q battery that I was using in my daily carry Emisar D4v2 flashlight. The D4v2 has battery indicator RGB leds in it and I had noticed that my light was losing its charge between uses. At first I thought I had just used the light more than I realized, but after I carried my Convoy S2+ shorty for a week, I noticed the D4v2 was still self draining. So I gave it a full charge and went back to my voltmeter for daily checks and yup… it is indeed self discharging. Note that I didn’t check it for a week at the end of my chart as I knew it was gone at that point. The frustrating part about this one is that this battery wasn’t that old. I label all of my li-ion batteries with the date I got them and this battery was from 8/2020, making it just a year and a half old now.  While I don’t think I had an excessive amount of charge cycles on it, I will admit that since this battery was in my pocket hot rod light, it did get driven extremely hard a number of times. However I don’t think it’d been driven hard recently, so I’m not sure why it just decided to go bad on me. If you have any thoughts as to why this happened to a relatively “young” battery let me know. Fortunately I had a spare 30Q from my UV light that I replaced with a more powerful version, so I didn’t need to order a new one. However I do need a new Samsung 50E for my new UV and those have been out of stock for like 3-4 months now… these stock shortages on literally everything are getting mighty old.