Tiny Solar Charger

Less than one inch square solar charging board based on the bq25504 solar harvesting ic with onboard solar cell for low power applications

Parts

• KXOB25-04X3F-TR: MONOCRYSTL SOLAR CELL 22MW 2.07V
• TI BQ25504: Ultra Low-Power Boost Converter With Battery Management

Configuration

Currently configured for single cell li-ion batteries but I've tested it with supercapacitors with voltage ratings over 4.2v

BAT_OV = 4.2v BAT_UV = 3.0v

Configuration resistor values:

• R6 = 4.02M
• R7 = 16M
• R8 = 4.42M
• R9 = 5.49M
• R10 = 4.22M
• R11 = 5.9M
• R12 = 5.620M
• R13 = 3.830M
• R14 = 0.619M

Board Pinout and Overview

Todo/improvements

• Schematic specifies an inductor that I'm not actually using, switched to a higher max current
• Currently using inductor with 300ma max current, datasheet specifies >300ma