Good luck finding a NiCad 9v battery. They’re all Nickle Metal Hydride now and the “memory effect” you’d find hasn’t ever been nailed down, other than cell capacity mismatch tripping charger cycles early. Go searching for the actual history of it, based on satellite issues never quite reproduceable.
Just buy a few 9v NiMh battery and a decent charger.
Lithium Ion batteries are cool and all, but they’re not as stable a chemistry as you might like to think.
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