High efficiency bidirectional multicell battery balancer

March 05, 2013 // By Christoph Hammerschmidt
With the LTC3300-1, chipmaker Linear Technology addresses the fledgling market of batteries for electric and hybrid electric vehicles. The LTC3300-1 is a fault-protected controller IC for transformer-based bidirectional active balancing of multicell battery stacks. The device can also be used in high-power UPS/grid energy storage systems and general purpose multicell battery stacks.

All associated gate drive circuitry, precision current sensing, fault detection circuitry and a robust serial interface with built-in watchdog timer are integrated. Each LTC3300-1 can balance up to 6 series-connected battery cells with an input common mode voltage up to 36V. Charge from any selected cell can be transferred at high efficiency to or from 12 or more adjacent cells. Here are the device's development motivations:

  • Big batteries are expensive – they all degrade over time and lose capacity
  • Low cost / refurbished cells have greater capacity mismatch

Increasing stack capacity with mismatched cells done in 2 ways - either by using bigger batteries (solution cost ~ $1 - $2 per A-hr per cell) or by useing active balancing (solution cost ~ $2 - $3 per cell – depending on IBAL)

  • Active balancing maximizes run time and allows fastest charge rates

The LTC3300-1 offers highest energy recovery and fastest balancing time, resulting in minimal charge time). In addition, it offers numerous safety features and high cost efficiency through by six-cell integration

Key Technical Features

  • Bidirectional Synchronous Flyback Balancing of Up to 6 Li-Ion or LiFePO4 Cells in Series
  • Up to 10A Balancing Current (Set by External Components)
  • Bidirectional Architecture Minimizes Balancing Time and Power Dissipation
  • Up to 92% Charge Transfer Efficiency
  • Stackable Architecture Enables >1000V Systems
  • Uses Simple 2-Winding Transformers
  • 1MHz Daisy-Chainable Serial Interface with 4-Bit CRC Packet Error Checking
  • High Noise Margin Serial Communication
  • Numerous Fault Protection
  • Features48-Lead Exposed Pad QFN& LQFP Packages

Target Applications include electric vehicles/plug-in HEVs, high power UPS/Grid energy storage systems and general purpose multicell battery stacks.