Smart Batteries

Smart Batteries 1

What are Smart Batteries (SMBus)

Smart Batteries contain a BMS (Battery Management System) or SMBus (System Management Bus), which is an electronic system that manages a rechargeable battery (cell or battery pack), such as by monitoring its state, calculating secondary data, reporting that data, protecting the battery, controlling its environment, and / or balancing it. A BMS may monitor the state of the battery as represented by various items, such as:

  • Voltage: total voltage, or voltages of individual cells
  • Temperature: average temperature, or temperatures of individual cells
  • State of charge (SOC) or depth of discharge (DOD): to indicate the charge level of the battery
  • State of health (SOH), a variously-defined measurement of the overall condition of the battery
  • Current: current in or out of the battery

Advantages

  • Provides state-of-charge and full charge capacity, reflecting capacity estimations.
  • Records battery history, including cycle count, usage pattern, maintenance requirements, max error, etc.
  • Configures charger to the correct algorithm.
  • Reminds user of periodic service.
  • Protects battery from unauthorized use.

Limitations

  • Adds 25% to the cost of a battery.
  • Complicates the charger; most chargers for intelligent batteries are hybrid and also service non-intelligent batteries.
  • Requires periodic calibration.
  • Readout only shows state-of-charge and not actual runtime.

Simple Guidelines for Using Smart Batteries

  • Calibrate a smart battery by applying a full discharge and charge every 3 months or after every 40 partial cycles. Batteries with impedance tracking provide a certain amount of self-calibration.
  • A fuel gauge showing 100 percent SoC does not automatically assure a good battery. The capacity may have faded to 50 percent, cutting the runtime in half. A fuel gauge can give a false sense of security.
  • If possible, replace the battery with the same brand to avoid incompatibility issues with the device and/or charger. Always test the battery and the charger before use.
  • Exercise caution when using a smart battery that does not indicate state-of-charge correctly. This battery may be faulty or is not fully compatible with the equipment.