2S Li-Ion power system for FPV goggles (allows the use of full capacity potential of li-ion cells). This is the second version whitch is much easier to build compaired to V1 (and is also much smaller).

• 9V Step-Up from a 2S source
• On/off button
• Adjustable low-voltage alarm
• LED power and capacity indicator

Notes: Voltage divider is currently designed for 10v max.

C1,C5: 100nF C0603 Capacitor (2x)
C2: 10nF C0805 Capacitor (1x)
C3: 1uF C0805 Capacitor 25V (1x)
C4: 2.2uF C0805 Capacitor (1x)
LS1: Speaker CSS-0575B-SMT (1x)
Q1, Q2: BC848 30V 100mA SOT23-3 Transistor (2x)
Q3: IRLML6402 Power Mosfet (1x)
R8, R9: 5k6 R0603 Resistor (2x)
R7, R5: 10k R0603 Resistor (2x)
S1: MOMENTARY-SWITCH SMD 5.2MM (1x)
U1: WS2812-2020 LED (1x)
U2: LP2985 5V LDO Reg (1x)
•: ATTINY85 SOIC8 (1x)

• Produced PCB (0.8-1mm thicknes required for the case)
  
• U3V12F9 Pololu 9V Step-Up
  
• Printed case parts (use PETG because of the heat from the step-up. TPU for the relief)
  
• ISP flashing tool (and SOIC8 clamp) like USBTinyISP
  
• 1.5m 5.5 x 2.1 DC cable like this: https://www.ebay.de/itm/0-50-1-00-1-50-m-USB-DC-Kabel-5-5-x-2-1-2-5-mm-Winkelstecker-CU-15855/293148509182 (cut the USB and replace it with your own connector)
  
• 2S li-ion battery pack. 3500mah 18650 will last about 3.5h, 5000mah 21700 will last about 5h. 18650 DIY battery case see the V1: https://github.com/skaman82/PowerPuck
  

• Solder all the SMD parts and the step-up to the PCB
• Compile and flash the code with ArduinoIDE using an ISP programmer (use the right hardware package mentioned in the code)
• Connect to a 2S power source and test if everything is working
• Solder on the cables, put it in the pinted case and glue it together

Connect the battery. The device is powered on and the LED is showing the battery status as follows:

• GREEN: voltage is 4.20 - 3.65v per cell (full)
  
• YELLOW: voltage is 3.64- 3.45v per cell (half)
  
• RED: voltage is 3.44 - alarmvoltage (one third)
  
• BLINKING RED and beeping: voltage is below alarm voltage
  

• GREEN: voltage alarm at 3.35v per cell
• YELLOW: voltage alarm at 3.25v per cell
• RED: voltage alarm at at 3.15v per cell

• Press the button for 2 sek. to save your alarm setting and exit the setup menu