Battery and power systems

A robot at full charge is full of potential — literally. The moment you press start, a race begins. Motors hungry for burst current, a computer trickling through calculations, sensors pinging dozens of times a second: all of it draining the same battery. Design the power system badly, and the robot browns out mid-task, corrupts a file, or — if a lithium cell is pushed too hard — catches fire.

The power system of a robot is everything between stored energy and the components that consume it: the battery itself, protection circuits, voltage regulators, and power distribution wiring. Getting it right is as important as writing good software.

The battery

Most modern robots use lithium polymer (LiPo) or lithium-ion (Li-ion) cells. Both store roughly 150–250 Wh per kilogram — far more energy density than older nickel-metal hydride or lead-acid batteries. LiPo cells are flat and flexible, preferred in drones and legged robots where weight and shape matter. Li-ion cylindrical cells (like the 18650 format used in laptops and Tesla cars) are cheaper and more robust for ground robots.

Key battery specifications:

• Voltage: LiPo cells are 3.7 V nominal per cell; packs are assembled in series (2S = 7.4 V, 4S = 14.8 V) to match motor requirements.
• Capacity (mAh or Wh): How much total energy is stored.
• C-rating: How fast the battery can deliver current safely. A 5,000 mAh, 30C pack can deliver 150 A — enough to spin a large brushless motor at full throttle.

Voltage regulation

A robot's battery voltage drops as it discharges. A motor controller can handle variable voltage; a microcontroller cannot — it needs a steady 3.3 V or 5 V. Voltage regulators (linear or switching) perform this conversion. Switching regulators (also called DC-DC converters or buck converters) are far more efficient than linear ones and are the standard choice wherever the voltage difference is large.

Protection and distribution

Lithium cells can be permanently damaged — or ignite — if over-discharged, overcharged, or short-circuited. A BMS (Battery Management System) monitors cell voltages and temperatures and disconnects the battery if anything goes out of range. On larger robots, a power distribution board routes the battery to multiple subsystems, often with individual fuses or polyfuses for protection.

Why it matters

Underspecify the power system and every other engineering decision becomes unreliable. A motor that stalls can draw ten times its rated current; if the battery or wiring cannot supply that, the whole robot resets. Power engineering is often the last thing a robotics student thinks about and the first thing that causes a demo to fail.

The energy stored in a fully charged 5,000 mAh LiPo pack — enough to fly a racing drone for 8 minutes — is equivalent to lifting a 70 kg person roughly 14 metres off the ground.