I also have a few backup batteries ...
You probably need to ask Apple, not other end users (us). On the page Ferd II links are FAQs, and this FAQ language:
- Does Apple offer recycling?
- Yes. Apple Trade In lets you recycle any Apple device at an Apple Store location and on apple.com for free. Items accepted for recycling include the device as well as batteries, cables, cases, monitors, packaging and more. Free recycling is available to our commercial, education, and institutional customers. When we receive your device, it will be thoroughly inspected and assessed for reuse or recycling. Whether recycled or reused, all activities relating to the processing of your device will be managed in an environmentally responsible way.
suggests to me that "batteries" refers to the battery in the device. Batteries from a backup power supplies a usually lead-acid and likely don't have the same recycling processes as lithium-based batters used in phones, tablets, and computers.
Apple will know.
👉🏻 If Apple does not take them, try Staples. Among the battery types they accept, "Small sealed lead acid (SSLA/Pb)" are listed.
Their comprehensive list of what they accept is here: https://www.staples.com/stores/recycling