Simplifying solar-based battery charging: Page 5 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.
charging systems consist of a DC-DC switching battery charger, a microprocessor plus several ICs and discrete components in an attempt to replicate maximum power point control / tracking functionality. An alternative solution could be a solar module; however these are costly, not simple to design in (require software, firmware, etc.) and tend to lock on to false solar panel maxima and therefore do not operate as efficiently as possible. Fortunately, a simpler solution is at hand, thanks to a buck-boost solar powered battery charging controller.

An efficient solar-powered solution

Linear Technology has developed a simple, innovative high voltage buck-boost charging controller IC specifically for solar applications, one which requires neither software nor firmware development, thus greatly reducing time-to-market.

Figure 4: LT8490 typical application circuit

The LT8490, shown in Figure 4, is a synchronous buck-boost battery charging controller for lead acid and Lithium batteries, featuring automatic maximum power point tracking and temperature compensation. The device operates from input voltages above, below or equal to the regulated battery float voltage. The device’s full-featured battery charger offers many selectable constant-current constant-voltage (CC-CV) charging profiles, making it ideal for charging a variety of Lithium or lead acid chemistry types, including sealed lead acid, gel cells and flooded cells. All charge termination algorithms are provided onchip, eliminating the need for software or firmware development, thus reducing design cycle time.

The device operates over a wide 6 V to 80 V input voltage range and can produce a 1.3 V to 80 V battery float voltage output using a single inductor with 4-switch synchronous rectification. The device is capable of charging currents as high as 10 A depending on the choice of external FETs. The LT8490’s MPPT circuit enables a sweep of the full operating range of a solar panel, finding the true maximum power point, even in the presence of local maxima points caused by partial shading of the panel.  Once the true maximum power

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