Simplifying solar-based battery charging: Page 4 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.
(where the charger feeds the battery, and a load is connected to battery) is needed - the battery is the power source but also acts as a 'buffer' in this case.

What is Maximum Power Point Tracking (MPPT) and why is it needed?

Maximum Power Point Tracking is a technique that helps extract the highest amount of power from the panel under all operating conditions. Some of these non-ideal operating conditions include:

  • Panel is partially shaded (leaves, bird droppings, shadows, snow, etc)
  • Panel’s temperature variation
  • Panel’s aging

For example, in off-grid solar panel systems, failure of the power system is costly. Customers want to extract the most power they can from the panel. Further, they want to maximize the time interval needed between maintenance visits to the solar installation.

True active MPPT will seek out the optimum operating point under all conditions.  This results in less overall system cost because the smallest panel or smallest battery can be used, reducing the need to over design the system. True MPPT will find the best peak power point and reject false local maximum common in partially shaded panels (note: partial shading power patterns are determined by the number and arrangement of bypass diodes inside the panel).

A Simple IC Solution

An IC charging solution that solves the problems outlined above needs to possess many, if not all, of the following attributes:

•    Minimal software and firmware development time
•    Flexible buck/boost topology
•    Active MPPT algorithm
•    Simple, autonomous operation (no µP needed)
•    Termination algorithms for various battery chemistries
•    In-situ charging - to power a load while the battery is being charged
•    Wide input voltage range to accommodate various power sources
•    Wide output voltage range to address multiple battery stacks
•    High output/charging current
•    Small, low profile solution footprints
•    Advanced packaging for improved thermal performance and space efficiency
•    Cost-effective solution

Typical convoluted competing solar battery

Design category: 

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