SparkFun 5V/1A LiPo Charger/Booster Hookup Guide

Contributors: MTaylor
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Charging a Battery

When a voltage is supplied to the charger, the MCP73831 charge IC comes alive and starts making decisions on how to regulate. First, it regulates current to 500mA until a certain voltage is reached, then it regulates voltage until current goes (close) to zero. When this happens, the charger IC shuts off.

MCP73831 Charge Current Regulation

As shown in the MCP73831 datasheet, charge current drops as battery voltage rises

The charger IC is making decisions based on the battery voltage and output load, and can be tricked into an invalid mode. Follow these rules to get a reliable charge:

  • Turn on the battery switch before connecting the charger.
  • Consume no more than 20mA from the output terminals during charging.