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Battery upgrade

IMG_20260828_205917_438.jpg

2x Stock batter Upgrade battery
Model EREMIT 606090 HXJNLDC 7565121
Size 90mm / 60mm / 6mm 122mm / 65mm / 7.5 mm
Chemistry Lithium-Polymer Lithium-Polymer
Capacity 14.8Wh (4Ah) 30.34Wh (8.2Ah)
Nominal voltage 3.7V 3.7V
Discharge max continuous 2A 5A
Charging limit voltage 4.25V 4.2V
Mass 74g 136g
  • Connector: JST-PH 2.0mm (not included in upgraded battery)
  • Both batteries have protection ICs

Charging chip - MP2650

  • Datasheet: MP2650GV.pdf
  • 4V to 21V Operating Input Voltage (VIN) Range
  • Up to 5A Configurable Input Current (IIN) Limit (Up to 45W Total Power)
  • Up to 5A Configurable Charge Current (ICHARGE)
  • Configurable Battery Charge Voltage Regulation (VBATT_REG) Up to 4.5V/Cell
  • Up to 5V/3A USB On-The-Go (OTG)

Monitoring chip - MAX17320G20+

  • Datasheet: max17320.pdf
  • Battery Health + Programmable Safety/Protection
    • Overvoltage (Temperature Dependent)
    • Overcharge/Overdischarge/Short-Circuit Current
    • Over/Undertemperature
    • Undervoltage + SmartEmpty
    • Battery Internal Self-Discharge Detection
    • Ideal Diode Discharge During Charge Fault
    • Charging Prescriptions (JEITA)
    • Prequal Charge Control with CHG FET
  • ModelGauge m5 EZ Algorithm
    • Percent, Capacity, Time-to-Empty/Full, Age
    • Cycle+™ Age Forecast
  • Precision Measurement Without Calibration
    • Current, Voltage, Power, Time, Cycles
    • Die Temperature, 4 Thermistors ±1˚C
  • Cell Balancing with Internal FETs
  • SHA-256 Authentication
    • Nonvolatile Memory for Stand-Alone Operation
    • History Logging, User Data (84 Bytes)

Firmware

pocket-reform-sysctl-fw/src/sysctl.c void charger_init()

  // 2A max charge current, assumes 4000mAh cells.
  mps_reg_limits.charge_current = 1<<5 | 1<<3;
  // set all current limits to 500mA (should always be safe)
  int current_limit = 1<<3 | 1<<1;
  mps_reg_limits.input_i_limit1 = current_limit;
  mps_write_buf(MPS_REGSTART_LIMITS, sizeof(mps_reg_limits.all_regs), mps_reg_limits.all_regs);
  mps_read_buf(MPS_REGSTART_LIMITS, sizeof(mps_reg_limits.all_regs), mps_reg_limits.all_regs);
  mps_write_byte(0x0F, current_limit); // Input Limit 2
  • Charging current limit is 2A by default hard-coded in the firmware.
  • Upgraded batter can go up to 5A and charger chip can also go up to 5A so depending on rest of the circuit it should be increased (to seepsay to 4A to be on the safe side) to speed up charging.
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