Understanding Battery Basics for Robotics

Aug 28, 2024

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Battery Basics for Robotics

Introduction

  • Focus on batteries, particularly for combat robotics.
  • Information applicable to general applications (robotics, RC, hobbies).
  • Generalized information with exceptions.

Types of Battery Chemistries

  • Lithium Polymer (LiPo):
    • Most common battery type for hobbyists.
    • Nominal voltage: 3.7V per cell.
    • Fully charged: 4.2V; discharged: 3.2-3.3V.
  • Lithium Iron Phosphate (LiFe):
    • Nominal voltage: 3.3V.
  • Lithium-Ion:
    • Nominal voltage: 3.7V.
    • Hard shell battery.
  • Nickel Metal Hydride (NiMH):
    • Nominal voltage: 1.2V.
    • Largely out of fashion due to discharge rates and power density.
  • Nickel Cadmium (NiCd):
    • Another type of rechargeable battery, less common.

Battery Ratings

  • Capacity:
    • Measured in milliamp hours (mAh) or amp hours (Ah).
    • Example: 5,000mAh = 5Ah means can deliver 5A for 1 hour.
  • S Rating:
    • Number of cells in series (e.g., 3S = 3 cells).
  • C Rating:
    • Maximum discharge current = C rating x capacity.
    • Example: 75C on a 5,000mAh battery = 375A max current.

Battery Connections

  • Connectors:
    • JST RCY: For small robots.
    • XT Connectors:
      • XT30: Small robots (up to 3-12 lbs).
      • XT60: Medium (common for many bots).
      • XT90: Large bots.
  • Balance Charge Leads:
    • Used for balancing cells during charging.
    • JST XH connectors for balance leads.

Charging Batteries

  • Chargers:
    • Ensure charger can handle your battery’s cell count.
    • Charge rate should be 1C.
    • Example: A 5,000mAh battery should charge at 5A.
  • Safety Precautions:
    • Charge in a lipo bag or on concrete.
    • Do not charge damaged batteries (puffiness, nicks).
    • Dispose of batteries responsibly.

Safety Considerations

  • LiPo batteries can be dangerous due to chemical reactions when punctured.
  • Always monitor charging; do not leave unattended.

Conclusion

  • Understanding battery ratings (C, S, capacity) is crucial for applications.
  • Considerations for advanced battery usage are possible for custom packs and charging methods.

Future Topics

  • Interest for advanced battery tutorial.
  • Topics could include building custom battery packs and advanced charging techniques.