The MH-CD42 is a compact module designed for use with a single (1S) Li-Ion or Li-Po cell, or multiple cells connected in parallel.
At its core, the module uses the IP5306 power management chip, a robust solution for efficient power regulation both for charging and for discharging.
Many breakout boards from various vendors exist that are all built around this chip (or its Chinese clones, such as the FM5324GA). These boards share many similarities, as the IP5306 largely defines their behavior.
That’s why it is essential that you consult this comprehensive guide on the IP5306 first before you move on to this article which focuses exclusively on the specific details and nuances of the MH-CD42 breakout board.
Overview
This 16x25mm module integrates all necessary components for building power banks, portable chargers, or adding battery support to USB/5V devices.
Separate Input and Output Connectors
Because of the IP5306 specific power path management, the module uses separate USB connectors for input (charging) and output (power supply):
- VIN: Input connector for a 5V charging power supply. Can be connected to a USB connector if you want to use a USB power supply for charging.
- OUT 5V: Output connector. Provides 5V at a maximum of 2A. Connect one or more USB connectors of your choice if you want to supply power to USB devices, or connect a 5V DIY device (i.e. microcontroller breakout board) that you want to supply with portable power.
- BAT: connect the positive pole of Li-Ion or Li-Po battery. Make sure the battery supports 2.4A charging current and a maximum of 3.5A discharge current.
Understanding Power Output Paths
This module can either charge the battery or supply power. It cannot do both at the same time. Regardless, you can draw power while charging. How does that work?
The chip’s power path management uses the battery and boost converter to provide battery power when no external power is connected (no charging).
Once you connect external power to VIN, the boost converter is turned off, and charging begins. The power output will still continue to deliver power to the OUT 5V pin, however now this power is taken from the VIN pin.
This has a number of consequences you should know and consider:
- High Input Power Requirements: the chip charges the battery with up to 2.4A (10.5W) while simultaneously providing up to 5V 2.1A (10.5W) to OUT 5V. During charging, both is powered by the external power supply connected to VIN. The combined output power is 21W. Your external power supply must be capable of delivering up to 22W/4.5A at 5V.
- Short Interruption: the chip needs to switch power paths once a power supply is connected to, or disconnected from VIN. Supplying external power or removing it may therefore both cause a brief power interruption, potentially rebooting connected microcontroller boards. Adding a sufficiently large capacitor to the power input can mitigate this issue.
Push Button
A push button is mounted to the PCB. There is also a solder pad at one end of the push button, labeled KEY, where you can connect an external push button. Use a 10kΩ resistor to connect the push button to GND.
The button allows manual control of the power supply:
- Short press (>30ms but <2s): Turns on indicator LEDs and enables power output.
- Double short press: Turns off indicator LEDs and disables power output.
Torch LED
A torch LED can be connected in parallel to the push button using a 100Ω series resistor. The push button can then turn the LED on and off with a long press. The torch LED is designed to draw approximately 25mA.
When the push button is using a 2KΩ series resistor instead of a 10KΩ series resistor, the torch feature is disabled, and a long press is without function.
Charging Mode
The charger activates automatically when a power supply is connected to VIN**, charging the battery at up to *2.4A. It requires a 5V 2A input. For detailed charging specifications, refer to the IP5306 documentation.
The charging cut-off voltage is set to 4.2V, which is suitable for most Li-Ion and Li-Po batteries. The IP5306 supports higher cut-off voltages, and some modules like the X-150 provide solder bridges to customize this, however this module does not expose this option.
Supplying Power
The module provides 5V at up to 2A at pin OUT 5V. Advanced quick-charge protocols are not supported.
Four red SMD LEDs display charging status and battery state of charge in 25% increments. When the battery’s state of charge drops below 3%, one LED starts to blink. If the battery voltage drops below 2.8-2.9V, the over-discharge protection cuts off power.
If the load is very light (<45mA) for more than 32s, the automatic load removal detection will cut off power.
During charging, the load is powered directly from the input supply, not the battery. This behavior only applies to battery operation. While charging, the load remains powered regardless of the battery status.
Manual Mode
Manual mode allows direct control of the (battery-powered) output via the optional push button:
- Short press: Manually enters Standby mode and turns power output on.
- Double short press: Exits Standby mode and stops power output.
When the module is charging, the buttons have no effect, and OUT 5V is always powered.
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(content created Jan 14, 2025 - last updated Jan 15, 2025)