Besides the main battery, do any components inside MacBooks rely on any other batteries to operate? Besides the main battery used to power Apple notebooks, do current MacBooks have any other built-in non-rechargeable batteries that may need to be replaced after a certain period of time? I was thinking particularly about the SMC; I wasn't sure if that required any external power (other than the main MacBook battery) to function.
There is only one battery in any modern Apple Laptop, and so far as I remember, there have never been other batteries in any Apple laptops.
The PowerPC iMac and other PowerPC G3/G4 tower CPUs did require a button battery replacement for the internal clock. I replaced many of these batteries back in the day.