The Framework bios (at least recent ones, but not original, so maybe OP hasn't updated) allow for a setting that, if the power is plugged in continuously, it won't fully charge the battery, even if your normal power limit is 100%.
Here is a knowledgebase article that goes into the details:
https://knowledgebase.frame.work/en_us/framework-laptop-13-b...
You can also control this from userspace. On Linux, use something like:
You can manually specify a fixed maximum, which was available from 3.04 (which was the BIOS I had back in late 2022 when I got mine).
One interesting note in the new functionality is that charging will let the battery drain by some percent before recharging.