How do I choose a robot battery?

Choosing the right battery for your robot involves a few key considerations to ensure it meets your robot's power needs and operational requirements. Here's a breakdown:

Key Factors to Consider

1. Voltage:

   • The first step is to determine the voltage required by your robot's drive system and other components.
   • Voltage must match the specifications of the motors, controllers, and other electronic parts.
   • Example: If your motors require 12V, your battery should provide 12V.

2. Capacity:

   • Capacity dictates how long your robot will run on a single charge. This is typically measured in Amp-hours (Ah) or milliamp-hours (mAh).
   • Tailor your selection so that your robot will run for the length of time necessary.
   • To calculate run time, estimate the total current draw of your robot and divide the battery capacity by the current draw. Example: A 2Ah battery powering a robot that draws 1A will theoretically run for 2 hours.

3. Battery Chemistry:

   • Different battery chemistries offer varying performance characteristics, including energy density, discharge rate, lifespan, and safety. Common chemistries include:
     • Lithium Polymer (LiPo): High energy density and discharge rates, but require careful handling.
     • Lithium-ion (Li-ion): Good energy density and lifespan, commonly used in consumer electronics.
     • Nickel-Metal Hydride (NiMH): Safer and more robust than LiPo, but lower energy density.
     • Lead-Acid: Inexpensive and reliable, but heavy and bulky.

4. Discharge Rate (C-Rating):

   • The C-rating indicates how quickly a battery can be discharged safely.
   • Example: A 1Ah battery with a 10C rating can deliver 10A continuously.
   • Ensure the battery's discharge rate meets or exceeds the peak current draw of your robot.

5. Size and Weight:

   • Consider the physical dimensions and weight of the battery.
   • Ensure the battery fits within your robot's chassis and doesn't significantly impact its performance due to added weight.

6. Safety and Handling:

   • Choose a battery that is safe to handle and operate.
   • Consider features such as overcharge protection, short-circuit protection, and thermal management.
   • Always follow the manufacturer's guidelines for charging, discharging, and storage.

Example Battery Selection Scenario

Let's say you're building a small robot that needs to run for at least 1 hour continuously. The robot's motors and electronics require 12V, and you've estimated the total current draw to be 2A.

Here's how you might choose a battery:

1. Voltage: You need a 12V battery.
2. Capacity: To run for 1 hour at 2A, you'll need a battery with a capacity of at least 2Ah (2 Amp-hours). A slightly higher capacity will provide some buffer.
3. Chemistry: You might consider LiPo or Li-ion for their good energy density, or NiMH for better safety.
4. Discharge Rate: If your motors occasionally draw higher current during acceleration, choose a battery with a C-rating high enough to handle these peaks. For example, a 2Ah battery with a 5C rating can supply 10A continuously.
5. Size and Weight: Select a battery that fits comfortably within your robot's frame and doesn't make it too heavy.
6. Safety: Choose a battery with built-in protection circuits.