I have a 2016 with 90k, and have had 3 batteries. The first went out at 50k because it would not charge to 100%, the second went out at 75k with the same symptoms you have. You can watch the ICE mode get ready to kick in on the flow graphic. The car starts using max battery power under load or even flat consistant speed. They the ICE slams on, even though it is supposed to warm up first using reserve battery power (not good for engine). It also would not charge up to 100% Audi told me I had a bad charge cable and would not replace battery. My car has onboard charging so I don’t necessarily need a cable, so that was bs. It took video demostrations of onboard charging and all the bogus error messages that were popping up to get a new battery. I suffered for about 10K miles while proving it was the battery. I heavily use the battery, and minimize ICE use, and I don’t think the little battery can handle multiple full charges and depletions a day. The 3rd battery is working great after about 15k, so we shall see…