Simplifying solar-based battery charging: Page 7 of 7

May 06, 2014 //By Steve Knoth and Albert Wu
Simplifying solar-based battery charging
Steve Knoth, Senior Product Marketing Engineer, Power Products Group and Albert Wu, Design Manager, Power Products Group, Linear Technology Corporation explains how a buck-boost solar powered battery charging controller can offer an efficient solar-powered solution.
FAULT pins can be used to drive LED indicator lamps.  Charging current limits can be adjusted by changing as few as 1 or 2 resistors, and a charging time scale can be selected with the appropriate resistor divider. Other features of the device include: input and charge current limit pins, a 3.3 V regulated LDO output, status pins and a synchronizable fixed switching frequency.

The charging controller is available in a low profile (0.75 mm) 64-pin 7 mm x 11 mm QFN package. The device is guaranteed for operation from -40°C to 125°C.

Key device features include:

•    VIN Range 6 V to 80 V
•    VBAT Range 1.3 V to 80 V
•    Single Inductor Allows VIN Above, Below, or Equal to VBAT
•    Automatic Sweeps to Find True MPPT Point
•    Support of Many Types of Lead Acid and Lithium Battery Types
•    LED Drivers for Status Indication
•    Battery Charging Algorithms Built-in
•    Automatic Float Voltage Temperature Compensation
•    Input & Output Current Monitor Pins
•    Synchronizable Fixed Frequency: 100 kHz to 400 kHz
•    64-Pin 7 mm x 11 mm x 0.75 mm QFN Package

Conclusion

Solar power is green and plentiful, but can be less than reliable.  Varying temperature effects moving the MPPT point, aging, partial shading, the sun going down, bird waste, etc. can all reduce panel performance. Linear Technology has developed the LT8490, a buck-boost switching regulator battery charger that implements a constant-current constant-voltage (CC-CV) charging profile used for most battery types, including lead acid (sealed SLA, flooded, gel) and Lithium. It also provides automatic and efficient true maximum power point tracking for solar powered applications. No software or firmware development is required, thus greatly reducing system time-to-market. The device is also a cost-effective and simpler solution than large and complex convoluted competing charging systems. It greatly simplifies what was historically a difficult design task.

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