Summary of TINYCHARGER – SINGLE CELL LI-ION BATTERY CHARGER WITH MONITORING
TinyCharger is a compact Li-ion battery charger using an ATtiny25/45/85 microcontroller and TP4056 chip. It features selectable charging current (100–1000mA) via parallel resistors controlled by MOSFETs, with real-time monitoring provided by an INA219 sensor and an OLED display. The system ensures safety through under-voltage lockout, automatic recharge, and precise termination when current drops to 1/10th of the programmed value.
Parts used in the TinyCharger:
- ATtiny25/45/85 microcontroller
- TP4056 linear charger IC
- OLED display
- INA219 current shunt and power monitor
- MOSFETs for switching resistors
- Three resistors connected in parallel
TinyCharger is an ATtiny25/45/85-based, single-cell Li-ion battery charger with selectable charging current limit (100mA – 1000mA) and an OLED display for monitoring.
For battery charging the TP4056 is used. The TP4056 is a complete constant-current/constant-voltage linear charger for single cell lithium-ion batteries. The maximum charge voltage is fixed at 4.2V and the charge current can be programmed externally with a resistor. The total resistance is determined by three resistors connected in parallel, two of which can be switched on and off by the ATtiny via MOSFETs. The TP4056 automatically terminates the charge cycle when the charge current drops to 1/10th the programmed value after the final float voltage is reached. Other features include current monitor, under voltage lockout and automatic recharge.
An INA219 is used to measure voltage and current. The INA219 is a current shunt and power monitor with an I²C-compatible interface. The device monitors both shunt voltage drop and bus supply voltage, with programmable conversion times and filtering. A programmable calibration value, combined with an internal multiplier, enables direct readouts of current in amperes.
Read more: TINYCHARGER – SINGLE CELL LI-ION BATTERY CHARGER WITH MONITORING
- What microcontroller powers the TinyCharger?
The project uses an ATtiny25/45/85-based microcontroller. - How is the charging current limit selected?
The current is set between 100mA and 1000mA using three parallel resistors switched on or off by the ATtiny via MOSFETs. - Does the device support single-cell lithium-ion batteries?
Yes, it is designed specifically as a single-cell Li-ion battery charger. - Can the charge voltage be adjusted externally?
No, the maximum charge voltage is fixed at 4.2V by the TP4056. - How does the charger determine when to stop charging?
It automatically terminates the cycle when the charge current drops to 1/10th of the programmed value after reaching the float voltage. - What component measures the voltage and current?
An INA219 current shunt and power monitor is used for measurement. - Is there a display to monitor the charging process?
Yes, an OLED display is included for monitoring purposes. - Does the TP4056 offer protection against low voltage?
Yes, the TP4056 includes under voltage lockout functionality.
