A charging station for a ruggedized hand-held computer terminal used in manufacturing, warehouse, and route delivery applications required a 4-bay Li-ion battery CC/CV charger with individual buck/boost Pulse Width Modulation (PWM) controllers on each pocket. The customer indicated that the batteries did not need to be rapid charged, and that the 4-hour maximum charge time was acceptable.
Additional requirements were as follows:
- 4-pocket charger capable of charging 2-cell and 4-cell batteries
- 2-cell battery required buck converter
- 4-cell battery required buck-boost converter
- Power supply: maximum allowed 100W power supply
- Charge duration: allowed to charge in 4 hours max
- Charge current per battery: allowed 1.1A / bay max
The final design was a 4-bay Li-ion battery charger with VVT digital charge technology capable of charging a 2-cell or 4-cell battery pack with 40% less power. This was possible because the VVT charger could extend the CC stage and actively monitor the cell voltages, requiring less charging power. Thus, the system input power could be reduced by 40%. By implementing VVT charging technology, tests showed that the batteries could be fully charged within 4 hours with approximately 750mA maximum charge current. The net result of the reduced input power adapter was a significant cost savings to the customer. Not only did VVT reduce project cost, but it also provided a less stressful charge for the cells and lower subsequent thermal side effects.
Reduced System Redundancy
- PWM integrated into single microcontroller controlling all four pockets
- Eliminated the need for 4 integrated charging circuits
- Integrated data transfer, encryption, power management capabilities
Reduced Cost Of Total System
- Reduced power supply from 100 watt to 72 watts
- Total system cost reduction of 10-15%