Gaps in battery usage graph on Galaxy mobile device
It is an intended Google concept with M (Marshmallow) or later OS your device is not faulty. If there are any breaks in the history, it is an indication that the device was powered off during that period.
If there are break points in the graph even though you did not power off your mobile device, it is recommended to check your battery performance on Samsung Members App by following these steps:
For Galaxy Note9: Launch Samsung Members > Tap Test hardware > Tap Battery
For Galaxy S10 | S10+ | S10e : Launch Samsung Members application > Get help > Interactive checks >Tap Battery