A key challenge for energy storage and conversion technologies is finding simple, reliable methods that can identify device failure and prolong lifetime. Lithium plating is a well-known degradation process that prevents Li-ion battery fast charging, which is essential to reduce electric vehicle “range anxiety” and enable emerging technologies such as aerial drones and high-performance portable electronics. The ability to detect the initial onset of lithium plating from easily accessible voltage measurements would greatly improve battery safety and feedback controls modeling. In this work, we highlight the application of a differential open-circuit voltage analysis (dOCV) to detect when Li plating begins during a single charge for room-temperature fast charging. We also show that dOCV can identify the Li plating onset during cycling with sensitivity of 4 mAh plated Li per gram graphite, indicating that this method has commercial promise for online Li detection.