troubleshooting Ryobi 18v tools?

Started with them 10 years ago,have about 20 now,bunch of batteries,so just stuck with one system.

A few months ago my bower would start cutting out/dying after 5 minutes..if I feathered it,might run 30 seconds each time.Switching battery with a new one didn't help.
Don't think its the battery,it was warm,but not hot,would only need 5-10 minutes on charger.
Now my weedwhacker is doing it.
I suspect they are just getting worn out,and motor overheating?Somehow has a thermal cutout…