Is a 7% battery health drop normal for iPhone 11?

Batteries, like people are individuals. No two people age exactly the same and batteries don’t age the same either. The exact usage, chemical make, storage conditions, exposure to heat and cold and about a dozen other factors mean that every battery ages differently. Battery aging is not a linear (straight line) and degrades at different rates as the chemicals in the battery age and the other factors mentioned above. Apple expects your battery health to be at 80% after 24 months. If your battery health misses that expectation, contact Apple Support.

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That model was discontinued over 2 years ago. If it was somehow still sealed from the factory, the battery is very probably nearly toast at this point. Lithium-ion batteries do not like being left without a charge for long periods.

When the battery health drops below 80% it is time to be replaced. The iPhone 11 you purchased has most likely had the battery replaced once already and hopefully that was done by Apple or Authorized Apple Repair center. If the battery you now have is not a genuine Apple battery, then you will see unexpected results. Further service on a phone with an unauthorized repair may not be possible by Apple. That would be for them to decide.