Combined charger and discharger logic in one module provides a simple way of building powerbank-like power supplies.
Overview
Charging & discharging boards contain both the battery-charging logic to safely charge a battery, plus a DC-DC converter to convert the battery voltage to a stable output voltage. This is all that’s needed to turn a rechargeable battery into a power bank.
Even more so, such modules can be used in portable microcontroller devices, turning any regular development board into a battery-enabled development board.
Charger Component
The charger part in these boards usually does not differ fundamentally from the common chargers, i.e. TP4056. Pay attention to these three parameters:
- Charging Current: typically 1A, but can be different. Make sure the charger does not exceed the maximum charging current of the battery you are planning to use. For microcontroller projects, often affordable Li-Po pouch batteries are used which have relatively low charging rates of 0.5C. When using a 1000mAh battery, the maximum charging rate should not exceed 500mA.
- Chemistry: most chargers target Li-Ion/Li-Po batteries. You cannot use these to charge LiFePo4 batteries.
- Strings: the vast majority of small modules is designed for a single battery cell. If you want to charge batteries consisting of multiple cells, make sure the charger voltage matches.
You cannot use multiple 1S chargers to charge batteries consisting of more than one cell because this would cause short circuits since most chargers are not isolated and must share the same ground. Always use chargers dedicated to the number of strings your battery uses.
Discharger Component
The discharger component transforms the battery voltage to a constant output voltage, typically (but not limited to) 5V.
Depending on your battery voltage and the desired output voltage, the component uses a buck, boost, or buck-boost component.
For example, if a module is designed for a 1S Li-Ion battery and outputs 5V to power USB devices, then the module uses a boost converter to raise the input voltage from 3-4.6V to 5V. The same would be true for modules designed to supply 3.3V from a NiMH cell (1.2V).
Modules outputting 3.3V from a 1S Li-Ion battery use a buck-boost circuit since the battery voltage can be lower or higher than the output voltage.
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(content created Jan 11, 2025)