Waveshare UPS HAT: Battery Backup for Raspberry Pi

Power cuts are common across India, and unexpected shutdowns corrupt SD cards. The Waveshare UPS HAT provides battery backup for graceful operation and shutdown.

Variants

• UPS HAT (B): 2x 18650, 5V/3A, I2C fuel gauge, on-board charger
• UPS HAT (C): Single 18650, compact, 5V/2A
• UPS HAT (D): LiPo connector, ultra-slim

All support pass-through charging — Pi runs uninterrupted during switchover.

Hardware Setup

1. Insert 18650 batteries (observe polarity).
2. Mount HAT on GPIO header.
3. Connect USB-C power to HAT (not to Pi directly).

Battery Selection

• Use Samsung 25R/30Q, LG HG2, or Sony VTC6 cells. Avoid unbranded cells.
• 2500-3500 mAh per cell. Two 3000 mAh cells give 4-5 hours backup.
• Unprotected cells recommended — HAT has its own protection.

Runtime: Pi 4 idle ~3W. Two 3000 mAh cells = ~6 hours idle, 3-4 hours under load.

Battery Monitoring

import smbus2
bus = smbus2.SMBus(1)
def read_voltage():
    raw = bus.read_word_data(0x43, 0x02)
    return ((raw >> 8) | (raw <> 3) * 0.004
print(f"Battery: {read_voltage():.2f}V")

Safe Shutdown Script

Monitor battery voltage, initiate shutdown when below 3.2V per cell. Create a systemd service to run at boot.

#!/usr/bin/env python3
import smbus2, subprocess, time, logging
logging.basicConfig(filename='/var/log/ups-monitor.log', level=logging.INFO)
bus = smbus2.SMBus(1)
while True:
    v = read_voltage()
    if 0.5 < v < 3.2:
        logging.warning(f"Low battery {v:.2f}V")
        subprocess.run(["sudo", "shutdown", "-h", "now"])
    time.sleep(30)

Use Cases

• Home server (NAS, Pi-hole, Home Assistant)
• Security cameras — continuous recording during outages
• Weather stations — uninterrupted data logging
• Industrial monitoring — no data gaps

Frequently Asked Questions

Charge and run simultaneously?

Yes, all variants support pass-through charging.

Battery lifespan?

500-1000 cycles. At daily power cuts, expect 2-3 years.

Auto-boot on power return?

No auto-power-on after shutdown. Configure HAT’s wake-on-power if available.

Works with Pi 5?

Yes, but Pi 5 draws more. Use UPS HAT (B) with high-drain cells.

Conclusion

The Waveshare UPS HAT is essential for any Pi deployment where uptime matters. Battery backup prevents SD card corruption and service interruption during India’s frequent power cuts.

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