Rechargeable batteries play an increasingly important role in our lives, powering portable devices, sensors, solar energy systems, and even electric cars.
In this section, you’ll learn how chargers (and charging) work, with examples of chargers you can use in DIY projects.
Overview
Chargers ensure that a battery safely absorbs energy, preventing overcharging and reducing fire hazards.
Dedicated Chargers
Dedicated chargers are designed exclusively to charge batteries. Internally, they function as constant voltage constant current (CV CC) DC-DC converters, equipped with enhanced logic for features like automatic shutoff, under-voltage protection, and temperature control.
Combined Chargers and Dischargers
These devices allow energy to flow in both directions, effectively turning batteries into power banks:
- Charging: Works like a regular charger. For example, USB power is converted to the voltage and current required to safely charge the battery.
- Discharging: Converts the battery voltage into a stable output voltage. For instance, a boost converter can take the variable voltage of a 1S Li-Ion battery cell (3.0–4.2V) and output a constant 5V to power or charge USB devices.
Combined chargers consist of two separate DC-DC converters—one for charging and another for discharging. Compact modules that integrate both functionalities are widely available. For larger power requirements, you can also combine two standalone DC-DC converters, designating one for charging and the other for output voltage regulation.
Solar Chargers
Charging batteries using solar panels follows the same basic principles as other power sources, but solar panels introduce unique challenges:
- Voltage Range: Solar panels operate over a wide voltage range depending on sunlight conditions. Chargers must handle this variability, and boost-buck converters are particularly efficient as they work with voltages both above and below the desired output voltage.
- MPPT (Maximum Power Point Tracker): Solar panel efficiency varies with factors like sunlight, shading, temperature, and electrical load characteristics. Sometimes it’s more efficient to draw less than the maximum possible current if it results in a higher voltage, maximizing power transfer (I × V = W). MPPT DC-DC converters adjust their duty cycle to identify the point of maximum efficiency, often through algorithms or trial-and-error. While not mandatory, MPPT chargers can significantly improve energy harvest in variable conditions like shading or fluctuating sunlight.
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(content created Mar 03, 2024 - last updated Jan 11, 2025)