iFixit reported earlier this week
that Apple has activated a "dormant software lock" on some iPhones that's effectively locking out third-party battery replacement. The iFixit team explains that when an iPhone battery needs replacing, it'll display a "Service" message in the Settings > Battery menu. If a third-party vendor replaces that battery, even using a genuine Apple battery, that message will continue to display. To make the message go away, an Apple Genius or Apple Authorized Service Provider has to authenticate the battery, iFixit says. There's a microcontroller from Texas Instruments onboard iPhone batteries that communicates health information to the phone. That chip is paired with the phone via an authentication key. If the key doesn't match due to third-party replacement, you get the service warning without the battery health info. Assuming the replacement battery is in good condition, it'll work fine regardless of the service warning. The service warning does not affect expected battery life, nor does the replacement cause performance throttling.