12.9" iPads Pro have a very good battery life, lasting approximately 8 hours with a normal use of Newzik. This is more than enough for rehearsals and performance.
Bluetooth foot pedals have a very low energy consumption and most have a battery life of more than 100 hours. Moreover, on most bluetooth page-turning pedals, an indicator will signal that the battery is low a couple of hours before it runs out. If the pedal battery ever dies during a performance, you can always turn pages manually, using your finger.
For large orchestras and ensembles, we recommend having some spare hardware (at least iPads, Pencils and pedals) to be 100% safe. A 10% spare rate is more than enough. Thanks to Newzik's cloud-based structure, you can retrieve your whole library and edits on any device when you sign in to your account. For example, if a musician comes to a performance with an iPad on low battery, they will be able to sign in to their Newzik account on a spare iPad with a full charge and retrieve all of their sheet music and markings, in time for the concert!