I wonder why the battery arrived flat—aren't Li-ions charged to ~50% at the factory for maximum shelf life (or rather 30%, the max allowed for shipping)?
I don't think the battery in question had time to self-discharge: it's a model A2660 introduced with the iPhone 13 in 2021, and the Li-ion self-discharge rate is only several percent per month at full charge, with discharge plateauing at lower voltages.
I don't think the battery in question had time to self-discharge: it's a model A2660 introduced with the iPhone 13 in 2021, and the Li-ion self-discharge rate is only several percent per month at full charge, with discharge plateauing at lower voltages.