micki231 wrote:
As I mentioned earlier: I do not receive any warning. Laptop just turns off when battery is gone.
no warming. No red symbol of the battery. No pop-up window at 2 %
I'll have to check a Sonoma system, but I know with Big Sur & Ventura I get the macOS notification when the battery charge drops to 10% and that notice stays in place until I actually acknowledge it. I wonder if you have some third party software installed which may be interfering.
Plus, I wondering if your battery has developed a hardware fault that just is not registering in macOS or with the Apple Diagnostics. Coconut Battery which @PRP_53 suggested has a history of the battery's Full Charge Capacity (FCC) which may provide a hint of a failure, plus the app may have a different interpretation of battery health from monitoring the FCC over time. I have used the command line to monitor the FCC values while performing a stress test on the battery which tends to reveal weaknesses in the battery that don't usually show up in the Apple Diagnostics or macOS battery condition assessment. When the FCC value drops significantly when using the laptop under heavy load, the battery charge level can easily drop 5% which can be enough to bypass any macOS hibernation options to cleanly save the system. I haven't used Coconut Battery enough to know how it behaves, but it does have a free version which gives you basic details for you to check out.
FYI, when the battery charge is under 10% (the closer to 1% the better), you will more likely see the battery condition in macOS to change to "Service Recommended" (depends on how often macOS polls the battery for health information), or the diagnostic is more likely to fail (connecting the charger can sometimes cause the condition to disappear, but the charger is necessary for the diagnostics).