# v2¶

Charge the li-ion batteries using a solar panel and then charge USB devices using the li-ion batteries.

## Sketch¶

The sketch can be found here.

## Hypothesis¶

The TP4056 can be used to charge a 3.7V li-ion battery and then the battery can be used to charge other devices using the USB boost converter.

## Assumptions¶

• One 3.7V li-ion is being used to capture the soloar energy.
• The DPDT switch disallows the li-ion battery from charging and the USB boost converter being used at the same time.

## Procedure¶

### Circuit¶

Connect the solar panel to the IN+ and IN- of the TP4056.

Connect one NC throw of the switch between the solar panel and IN+ of the TP4056.

Connect the other NO throw of the switch between the IN+ of the boost converter and OUT+ of the TP4056.

Connect the 3V li-ion batter to the B+ and B- of the TP4056.

Connect the JST-PH 2.0 connector between the solar panel and the TP4056.

### Output¶

• The red LED on the TP4056 is on when the li-ion battery is charging via the solar panel.
• The blue LED on the TP4056 is off when the li-ion battery is charging via the solar panel.
• The red LED on the TP4056 is on off the li-ion battery is fully charged and the solar panel is on.
• The blue LED on the TP4056 is on when the li-ion battery is fully charged and the solar panel is on.
• The red LED on the boost converter is off when the solar panel is on.
• The red LED on the boost converter is on when the solar panel is off.

WIP

WIP

WIP

WIP