Apple has made iOS 11.3 Beta available for developers. This update can help solve or at least alleviate the current battery throttling issue that lowers performance on older iPhones to avoid the sudden shutdown issue that users have experienced. Apple is currently offering discounted battery replacement for affected iPhones and this iOS 11.3 system update, which will be made available to all users in the spring, should help.

Apple says iOS 11.3 improves this performance management feature by periodically assessing the level of performance management necessary to avoid unexpected shutdowns. If the battery health is able to support the observed peak power requirements, the amount of performance management will be lowered. If an unexpected shutdown occurs again, then performance management will increase. This assessment is ongoing, allowing more adaptive performance management.