Genset Starting Education Module #7

Key Factors for Reliable Redundant Battery Systems

Redundant battery system application and maintenance considerations.

Special considerations are required when using redundant batteries to ensure reliability and performance. While a redundant system offers significant excess capacity under normal conditions (when both batteries are fully charged and operational), the failure of one battery can lead to performance degradation far worse than simply losing half the system's capacity. This is due to the following effects:

• Increased Power Losses

• • Joule’s Law¹ amplifies power losses across all components of the electric starting system, including:
    • Batteries
    • Best Battery Selector (BBS)² systems
      • Battery cables
      • Starter motors
    • Learn more about Joule's Law of Electric Heating and its impact on redundant systems.

• Electrochemical Performance Drop

• As highlighted in SENS Genset Starting Education Module #2: Engine Start Battery Performance Characteristics, batteries deliver less total energy as the discharge power rate increases.
• This limitation is driven by electrochemical reaction kinetics and diffusion characteristics.

To mitigate these challenges, each battery, charger, and cable in a redundant starting system must be:

• Individually Specified: Components must meet performance requirements as if each battery is operating solo.
• Thoroughly Tested: Rigorous testing ensures each element can function independently.
• Regularly Maintained: Preventative maintenance is critical, as any component may need to operate alone in an emergency.

In life-critical scenarios, one battery might be the sole power source keeping your genset operational. Prioritizing maintenance and sizing ensures redundant systems are truly reliable when it matters most. Learn more about genset applications and their critical role in maintaining operational reliability.

Ensuring Optimal Maintenance for Redundant Battery Systems

Recommended maintenance appropriate to redundant battery systems.

 

Periodic checks and proper testing are essential to uncover hidden performance issues and ensure redundant systems operate as intended.

Redundant battery systems provide additional starting power, but it is this same redundancy can conceal issues with one of the batteries. To ensure both batteries function reliably:

• Temporarily disable one battery during maintenance.
  • Observe and measure the engine crank performance powered solely by the active battery.
  • Verify that the active system delivers its originally specified performance.
• Address any deficiencies immediately to ensure the expected redundancy is available when needed.

Additional Considerations

• Joule’s Law: Power dissipation in a linear resistance increases exponentially with current.
  • Doubling the current results in a fourfold increase in power loss (P = I² * R).
• Best Battery Selector (BBS):
  • Designed to deliver power from two separate batteries for redundancy.
  • The BBS is a passive diode steering device that:
    • Automatically supplies the load from the stronger battery.
    • Prevents parallel connections, ensuring a weak or failed battery does not drain the good one.

By following these maintenance recommendations, you can ensure your redundant battery system delivers reliable performance when it matters most.

References

1. Joule’s law: power dissipation in a (linear) resistance is proportional to the square of the current (P=I2*R). Doubling current causes a fourfold increase in power loss. 
   
   
2. Best Battery Selector, the purpose of which is to deliver power from two different batteries for the purpose of battery redundancy. The BBS is a passive diode steering device that automatically supplies the load from the stronger of two batteries. In case one battery is weak or has failed the BBS prevents parallel connection of two batteries so that a bad battery does not drain the good one.