Hello Matt,
I would advise you to observe/document the problem with your A13 more closely. I don't know if this was a one-time problem or if it really starts losing battery at 22% quicker and is a repeatable problem. Even if determining the battery capacity is not that easy, a smartphone should be able to estimate the battery level. This is also important for the user, otherwise you will assume completely wrong circumstances and can even get into problems if the device incorrectly estimates the battery life.... 22% battery should last at least as long as from 44% to 22%. You rely on the device and the information to a certain extent.
I would therefore recommend monitoring the device when not in use (e.g. at night) and noting the battery level.
I don't know how old your device is either, maybe the battery has a problem and loses too much voltage at a certain point. But I have no idea how or whether the devices determine the battery level, there is absolutely no information from the manufacturer. It's also worth looking for external causes. The standard suggestion is to look for apps, perhaps the device was in a corner with poor reception and more power had to be used to maintain the connection, updates. You should rule out everything as a cause.
Example:
My A14 and a second A14, which definitely has some strange problem and always starts losing battery massively after 10 days of system runtime.
https://eu.community.samsung.com/t5/galaxy-a-series/galaxy-a14-increased-battery-drain-after-10-days... 3
