HJC-HC-10F-2.7V

The HJC-HC-10F-2.7V backup time depends on RTC current consumption: Backup time = 0.5 × C × (Vmax² - Vmin²) / I. Example calculations: 1) Low-power RTC (1µA): Time = 0.5 × 10F × (2.7² - 1.8²) / 1µA = 0.5 × 10 × 4.05 / 1µA = 20,250 seconds ≈ 5.6 hours, 2) Ultra-low-power RTC (0.1µA): Time = 56 hours, 3) Standard RTC (5µA): Time = 1.1 hours. Actual backup time also depends on: minimum operating voltage of RTC, leakage current of supercapacitor, and temperature. For longer backup, use larger capacitance (22F, 50F) or multiple capacitors in parallel. The supercapacitor can be recharged quickly when power returns, unlike batteries that require slow charging.

Calculate based on your RTC current consumption; use C = 2 × I × t / (Vmax² - Vmin²) to determine required capacitance.

Charging the HJC-HC-10F-2.7V requires current limiting: 1) Current Limit - Maximum recommended charging current is typically 1-10A for this size; use 100mA-1A for standard charging, 2) Voltage Limit - Do not exceed 2.7V; use voltage regulator or clamp, 3) Simple Circuit - Resistor in series: R = (Vsupply - Vcap) / Icharge. For 5V supply, 100mA charge: R = (5-0)/0.1 = 50Ω (use 47Ω standard), 4) Active Circuit - Use constant current source or dedicated supercapacitor charger IC for faster, controlled charging. Charging time: From 0V to 95% charged: t = 3 × R × C. With 47Ω resistor: t = 3 × 47 × 10 = 1410 seconds ≈ 24 minutes. For faster charging, use lower resistance or active current source. Always include overvoltage protection to prevent exceeding 2.7V.

Use series resistor for simple applications; dedicated charger IC for fast charging or precise control.

Yes, two HJC-HC-10F-2.7V supercapacitors can be connected in series for 5V applications: 1) Series Configuration - Two 2.7V cells in series provide 5.4V rating (good for 5V systems), 2) Total Capacitance - Ctotal = 10F/2 = 5F (capacitance halves in series), 3) Voltage Balancing - Essential! Use balancing circuit to prevent one cell from exceeding 2.7V, 4) Simple Balancing - Use 1kΩ resistors across each cell for passive balancing, 5) Active Balancing - More efficient; use dedicated IC. Energy storage: E = 0.5 × 5F × (5.0² - 3.0²) = 40J (usable from 5V to 3V). Applications: 5V backup power, USB power buffering, 5V microcontroller backup. Always monitor individual cell voltages during development to verify balancing is working correctly. HJC also offers pre-configured 5V modules with built-in balancing.

Use two in series with balancing circuit for 5V applications; consider pre-built modules for simplicity.

The HJC-HC-10F-2.7V self-discharge characteristics: 1) Initial Drop - Voltage drops 5-10% in first few hours after charging due to charge redistribution, 2) Long-term Self-Discharge - Typically 5-20% per day depending on temperature, 3) Temperature Effect - Self-discharge doubles approximately every 10°C increase, 4) Leakage Current - ~30µA at 25°C after 72 hours. Self-discharge mechanism: Internal leakage current slowly discharges the capacitor. At 25°C: ~10-15% voltage drop per day. At 65°C: ~30-40% per day. For backup applications, this means: 1) After 1 day: ~85-90% voltage remains, 2) After 3 days: ~60-70% voltage remains, 3) After 7 days: ~30-50% voltage remains. For applications requiring long hold-up times, calculate based on initial voltage after accounting for self-discharge. For very long backup (weeks), consider larger capacitance or periodic topping charge.

Account for 10-20% daily self-discharge in backup time calculations; use larger capacitance for long hold-up requirements.

Temperature significantly affects HJC-HC-10F-2.7V performance: 1) Capacitance - Relatively stable across temperature range; slight increase at low temperatures, 2) ESR - Increases at low temperatures (2-3x at -40°C vs 25°C); decreases slightly at high temperatures, 3) Leakage Current - Doubles approximately every 10°C increase; very low at cold temperatures, 4) Voltage Rating - Must be derated at high temperatures; do not exceed 2.5V above 65°C, 5) Lifetime - Higher temperatures reduce cycle life and calendar life. Operating recommendations: 1) Optimal Range: -20°C to +45°C for best performance, 2) Extended Range: -40°C to +65°C with derating, 3) High Temp: Reduce voltage to 2.5V max above 65°C. Cold temperature performance is generally good - ESR increases but capacitance is maintained. Supercapacitors perform much better than batteries at low temperatures.

Operate within -20°C to +45°C for best performance; derate voltage at high temperatures.

The HJC-HC-10F-2.7V maximum discharge current depends on ESR and acceptable voltage drop: 1) Continuous Current - Limited by thermal considerations; typically 1-2A continuous, 2) Peak Current - Can deliver short pulses of 5-10A for milliseconds, 3) Calculation - Imax = (Vcap - Vmin) / ESR. At 2.7V, 0.5Ω ESR: Imax = 2.7V/0.5Ω = 5.4A (until voltage drops). For pulsed applications: 1) LED Flash - 1-3A for 100ms is typical, 2) Motor Start - 5A for 1-2 seconds, 3) RF Transmit - 10A pulses for microseconds. Thermal considerations: P = I² × ESR. At 2A: P = 4 × 0.5 = 2W heating - requires adequate cooling. For high-current applications, use multiple capacitors in parallel to reduce effective ESR and distribute heating.

For continuous currents above 1A, use parallel capacitors; for pulse applications, calculate based on allowable voltage drop.