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lipo_mod.md

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MOD : Using LiPo Batteries

Warning: LiPo batteries can be very dangerous! Handle them with care and make this mod at your own risk!

Preliminary stuff

You'll need:

  • 18650 LiPo Battery with tabs
  • an SX1308 Step-Up Converter (PCB signature is HW668)
  • a TP4056 with protection for recharging the battery (or use the method you prefer for re-charge the battery)
  • 3D-print the arlok_18650_holder.stl
  • additional 2 M3 screws, Allen bolt socket cap, 12mm (length of threaded part - 15mm total) + nuts
  • some strong double-sided tape

OPTIONAL

  • Display having leds in shape of a battery ("Battery display"), indicating charge level of 1S Lipo Battery (PCB signature is XW228DKFR4)
  • Alternate "Plate Top" STL arlok_plate_top_1sdisplay.stl having a slot for the TP4056 with protection and the square hole for the above mentioned display

Boards

You'll remove:

  • Battery Holder for 4AA batteries
  • Battery Holder for 3AA batteries
  • X2 (VDD) Screw Terminal 2pin

You'll not use anymore:

  • Power Jumper (you can close it with a bridge)

Schematic (basic)

18650 powering

Schematic (with 1S battery display)

18650 powering + display

How-to

  • Fix the 18650 battery on the bottom of the robot using the arlok_18650_holder.stl, screws and bolts
  • Solder a red cable from the + tab of the battery to 1 pin of the round pushbutton with retain or lever switch
  • Solder a red cable from the free button/switch terminal to the + Input terminal of the SX1308 module
  • Solder a black cable from the - tab of the battery to the - Input terminal of the SX1308 module
  • Turn on the button/switch and check with a multimeter the SX1308 module: adjust it using the multi-turn trimmer on it for 5.6 / 5.7 volts (the Diode D1 will lower the voltage of about 0.6-0.7V)
  • Turn off the button
  • Attach the SX1308 module on the top of a servo bracket using double-sided tape (or make and share your own design)
  • Solder a red cable from the SX1308 + output to the + of Vservo X1 screw terminal
  • Solder a black cable from the SX1308 - output to the - of Vservo X1 screw terminal
  • (optional) Solder a cable, having a female dupont terminal, on the + Input terminal of the SX1308 module along with red cable already soldered: this can be used for checking the battery voltage reading from an Analog Input. The female dupont terminal can be connected to one free analog input terminal (A2 - you can use/take inspiration from the explorer lipo programming example)
  • Set the Jumper JP1 in the VSERVO position

OPTIONAL

  • Solder red and black cables on the "Battery Display" and connect them to VIN and GND of the SX1308 PCB

Now all the robot parts (logics and servos) will be powered from the same battery: Logics will be powered at about 5V and servo at about 5.6V.
The explorer program contain some instructions for reading the battery and show it on display.

For charging the battery you must:

  • Turn off the button/switch on the back
  • Attach outputs of the TP4056 module on the battery using alligator clips (or make and share your own design)
  • Battery will be fully charged when blue led on TP4056 module turns on