Charging controller with maximum power point tracking

29th January 2021
Mick Elliott

The LT8491 buck-boost battery charging controller from Analog Devices features Maximum Power Point Tracking (MPPT), temperature compensation and I2C interface for telemetry and control.

The device operates from input voltages above, below or equal to the regulated battery float voltage.

It offers three selectable Constant Current Constant Voltage (CC-CV) charging profiles, making it ideal for charging a variety of battery chemistry types including sealed lead acid, gel and flooded cells, and Li-Ion. All charge termination algorithms are provided onboard, eliminating the need for software or firmware and thus reducing design cycle time.

Operating over a 6V to 80V input range the LT8491 can produce a 1.3V to 80V battery float voltage output using a single inductor with 4-switch synchronous rectification.

The device is capable of charging currents as high as 10A depending on the choice of external components, and it may be paralleled with multiple LT8705 (80V buck-boost controller) devices for higher power operation.

The LT8491 can do 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 point is found, the charge controller will operate at that point while using a dithering technique to track slow changes in the maximum point.  

By using these methods, it can fully utilise nearly all the power generated by a solar panel even in non-ideal operating environments.

The device can perform automatic temperature compensation by sensing an external thermistor thermally coupled to the battery.

The I2C interface provides complete control of the charger as well as input/output voltage, current, and power values.

The LT8491 is available in a low profile (0.75mm) 64-pin 7mm x 11mm QFN package and is guaranteed for operation from -40°C to 125°C.

The device has an internal EEPROM for Configuration Storage

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