I make a lot of coin cell powered projects and use the LIR2032 batteries quite regularly. The rated cycle of the LIR batteries are 500 cycles but in reality, it does not last that long. I did a bit of research and found out that the cheap Chinese charger was the culprit. Another thing is that you need to insert two batteries at the same time to charge. The voltage and charge of two batteries will be different and this will eventually ruin one of the batteries.

I had two choices to make.

I could either rant about these faults or could make my own improved version.

I took the later path and made my own coin cell battery charger.

A lithium battery should be charged in three stages. If the battery voltage is less than 2.9V then it needs preconditioning. The battery is trickle charged. This phase brings the battery voltage up to a safe level for full current charging. Then a constant current 30mA full-throttle charge and finally a constant voltage trickle charge to keep the battery topped up.

Feasures:

• Standard 5V USB powered device.
• micro USB connection.
• Charging current approximately 30mA.
• Charging time approximately 4 hours (Depends on battery capacity).
• Smart three stage charge controller.
• Current monitor.
• Undervoltage lockout.
• Preconditioning of low voltage batteries.
• Two LEDs show power and charging status. BLUE led- power on, RED led- charging.
• Automatically cuts off power when the battery is fully charged.
• Small size.
• High accuracy preset output voltage regulation (+/-1.0%).

How to Use:

Slide the coin cell in the right way. Power the device with a USB port. The BLUE led will turn on indicating it is getting power from the USB port. When the battery is charging, the RED led will turn on. It takes about 4 hours to fully charge. The BLUE led will turn off to let you know when it is fully charged.

Note:

• Only use rechargeable LIR2032/ LIR2025 cells.
• Do not charge unattended.
• Do not charge damaged cells.
• Do not insert the battery in reverse polarity. It will damage both the battery and the circuit.
• Do not try to charge non-rechargeable batteries.-