You said that you have problems with all your batteries? At which temperature did you limit them?
I have 3 phones crunching atm and set them to 70% cpu and 32°c limits. Or is swelling inevitable?
I do try to cool them off. With various techniques, sometimes not worth the effort but it's fun doing it:
Placing usb fans, putting coins (hah it works slightly) and/or a glass of water on the waterproofed ones but laying them face down on window sills in the shadow side is fantastic, apparently natural stone (I got travertine ones) is exceptional at absorbing heat as I found out. Sometimes lowering temperature by almost 10 degrees celsius.