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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) (see this and this)
    • Datasheet: ePH.pdf
    • Max current: 2 A
  • 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 but PH connectors only do 2 A max so can't increase charging current.
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