Ever since the Android 10 security patch update, when my battery gets to 25% I can actually watch it drop a percentage every few seconds. Even after I plug in the charger, which I am now also getting the compatibility and check your connection warning too, it continues to drop. I plugged in the charger at 11 percent and even after I successfully plugged in the charger and shut off the screen to standby mode I still watched it continue to drop until it hit 2% battery life left and stopped. Yesterday it dropped to zero and shut off after I successfully plugged it into the charger. As long as I don't allow it to drop below 25% I'm fine. I also have issues with websites and apps freezing up which never happened before and I have 1.8 GB of RAM available. This is frustrating to say the least.
Like the last two replies, my Galaxy A20 battery level starts to drop quicker than usual after around 25% then once it hits 15% and gives me the plug in charger warning, it'll drop even faster. Then plug in the charger and literally watch it drop 1% per couple seconds.
It won't even begin to charge until it's reached 0% (luckily the phone stays on).
I am also inclined to believe this started only after the latest security update (September 1st)
This issue is pretty blatant and I would have noticed it earlier.