Power Monitor setup on ArduPilot Copter 3.6+ - Blog - ArduPilot Discourse
APM Current Sensor Power Module - Wiki
Pixhawk2 new Power Module for Pixhawk APM 3S to 6S Battery
APM/Pixhawk 180A Hall Sensor Inductive Galvanometer UBEC 12S Power Monitor Module Ammeter Current Meter Molex /JST-GH 1.25mm for RC Drone FPV Aircraft Airplane - Newegg.com
External Battery Monitor with ADC
PX4 Configuration - Multi-robot Systems Group UAV System