Clamshell mode powering 2 external monitors now with 2nd swollen battery
Working from home for years now, I've primarily had my laptop (Late 2013 model) in clamshell mode in a vertical holder made for this exact purpose. Connected to the MacBook Pro are two external monitors. I'm about to have my second swollen battery replaced but according to the thread I found below, clamshell mode should protect my battery from overcharging since I can't unplug it as this is required to power the external monitors. Am I unfortunate to get junk batteries or is the post I'm referencing below incorrect information? FWIW, I'm running Mojave 10.14.6 for specific reasons and not the latest OS.
https://discussions.apple.com/thread/251672590
While I'm aware that this laptop is going on 8 years old, should I have needed to replace two batteries already?? Any insight would be greatly appreciated.
MacBook Pro 15″, macOS 10.14