Energy management in robotic systems has traditionally been driven by onboard energy limitations. In collaborative multi-robot systems, however, it concerns not only conserving energy but also improving how efficiently robots use their time, how reliably they operate, and how long they remain autonomous. This thesis investigates energy management strategies for collaborative multi-robot systems, emphasizing scenarios where both energy consumption and robots' time of use matter equally. It combines practical system development, realistic energy modeling, scheduling optimization, and energy-aware path planning, supported by both real robot deployment and simulation. The motivation arises from ambiently-powered systems that harvest renewable energy such as sunlight or other environmental sources. Since harvested energy rarely sustains robots fully, they must rely on charging infrastructure like docking stations or opportunistic wireless transfer. In such environments, efficiency means maintaining continuous task execution and maximizing productivity while minimizing interruptions caused by charging or idle states. These challenges are especially relevant in warehouse automation, environmental monitoring, agriculture, and surveillance. The first research question investigates managing idle energy consumption. A low-power Energy Management Module (EMM) was designed and deployed on a real TurtleBot3, enabling control of active, standby, off, and recovery modes. It reduced idle-mode power from roughly 7 W to 26.2 microwatts, showing hardware-level management can extend operational lifetime. The second question examines realistic energy modeling and embedding charging decisions into scheduling. Detailed consumption data from the TurtleBot3 built an accurate model integrated into ROS-Gazebo. Incorporating charging into scheduling reduced total mission makespan by up to 15%. The third question explores scaling scheduling to larger systems. An Adaptive Particle Swarm Optimization approach improved convergence, while a hybrid multiverse-based parallel framework exploited the swarm's own distributed processing, making scheduling five times faster. The fourth question extends scheduling to dynamic environments like UAVs. The EA-MAOSS framework integrated distributed reinforcement learning, adaptive charging, and digital twin-based modeling. It reduced makespan by up to 30%, increased cumulative rewards, and cut charging events by over 50% versus fixed-threshold approaches. The fifth question addresses exploiting energy-harvesting opportunities during navigation. The H-CMARL-DE framework combined hierarchically conditioned multi-agent reinforcement learning with meta-level differential evolution for decentralized coordinated path planning. It achieved up to 240% higher harvesting efficiency than classical ROS-OMPL planners and CTDE-based methods, while staying within 10% of shortest-path length. Collectively, these contributions integrate low-power hardware, realistic modeling, distributed optimization, reinforcement learning, and energy-aware navigation, improving the efficiency, scalability, and long-term autonomy of ambiently-powered robotic systems.