jyesmith/18650-backpack

Battery management system for your FPV goggles.

18650-Backpack

• 9V regulator... no more Fatshark alarm!
• Settable voltage alarm. Default 3.10V with a secondary alarm at 3.00V (0.10V below set alarm voltage). Configurable through the UI.
• Beeper alarm and flashing OLED.
• Monitors over all voltage, cell 1 and cell 2. When using a Fatshark battery pack without a balance wire the cell voltage is pack voltage divided by 2. This does not mean the batteries are balanced.
• Current sensor.
• mAh consumption.
• On time.
• Retains on time and mAh when powered down. Can be cleared for a new battery by pressing any button while plugging in the battery.
• 12 character callsign. Configurable through the UI.

https://www.youtube.com/watch?v=n1eo8pUAjkk

Bill of Materials

The below links are give for reference so you know what to search for from your favourite/local supplier.

A hot air rework station (such as the 858D linked below) is required if you use the following BOM. I used the Digispark Attiny85 and INA219 break out boards as donors for the 18650 Backpack. This make life easier than ordering ALL of the components separately.

https://www.banggood.com/858D-220V-Hot-Air-Soldering-Rework-Station-Handle-Handle-Stand3-Nozzles-p-1129100.html

• Download the Gerber zip file from the PCB folder and upload it to https://jlcpcb.com, or your preferred PCB manufacturer.
• Digispark Attiny85 (cheap on ebay) https://www.banggood.com/ATTINY85-Mini-Usb-MCU-Development-Board-For-Arduino-p-971122.html
• 2 x INA219 High Side DC Current Sensor (cheap on ebay) https://www.adafruit.com/product/904
• Pololu 9V Step-Up Voltage Regulator U3V12F9 https://www.pololu.com/product/2116 ( for the Aussies https://core-electronics.com.au/pololu-9v-step-up-voltage-regulator-u3v12f9.html)
• OLED 128x32 https://www.banggood.com/0_91-Inch-128x32-IIC-I2C-Blue-OLED-LCD-Display-DIY-Oled-Module-SSD1306-Driver-IC-DC-3_3V-5V-p-1140506.html
• AT24C02 SOP-8 Serial EEPROM https://www.ebay.com.au/itm/10pcs-AT24C02-SOP-8-Serial-EEPROM-Memorizer-2KB/271441366188
• Buzzer https://www.banggood.com/5-PCS-Super-Loud-5V-Active-Alarm-Buzzer-Beeper-Tracker-95_5mm-for-Racing-Drone-p-1117207.html
• 2 x Tactile Push Button https://www.banggood.com/100Pcs-5-Pin-Tactile-Push-Button-Switch-Tact-Switch-6-X-6-X-3_1mm-SMD-p-1018679.html
• Power jack https://www.banggood.com/DC-Tip-Power-Plug-Jack-Connector-Dual-5_5-x-2_1mm-Male-Right-Angle-Cord-Cable-p-1161332.html
• 2s balance (male and female) https://www.banggood.com/40-set-2p-3p-4p-5pin-Right-angle-JST-XH-2_5mm-Male-Female-Lipo-Balance-Connector-p-1160571.html

Flashing the Attiny85

The below can also be done with an Arduino Nano.

https://www.instructables.com/id/Program-an-ATtiny-with-Arduino/

• 1 - Ground
• 2 - D11
• 3 - D12
• 4 - D13
• 5 - D10
• 6 - +5V

Core and Libs

• https://github.com/damellis/attiny
• https://github.com/datacute/Tiny4kOLED
• https://github.com/jmendeth/power-trinket/blob/master/sketch/_Adafruit_INA219.h (Adafruit_INA219.h using TinyWire)

18650-backpack's Issues

5 second EEPROM writes will cause write exhaustion in under 200 hours

Logic: 100k writes / writes per hour
Writes per hour = (60/5)*60

Either slow the rate, or do some load balancing (change EEPROM address every 100k writes?) since it's 100k per cell, not for the entire flash.

smart cable for Fartshark

this is project can modifi to smart cable for Fartshark ?
Feature :
ON/OFF power
display volt ampe when Fs work
alarm batterry ,auto Off when not use a long time
thanks