Battery Types and Selection

🔋 Battery Types and Selection for Solar IoT

🔋 What You'll Learn:

📊 Compare 4 battery types: Li-ion, LiFePO4, Lead-Acid, NiMH
🔋 Calculate required capacity for your sensor
💰 Choose the best value for your budget
⚠️ Learn critical safety rules for lithium batteries

📊 Battery Comparison

🔋 Li-ion (18650): 3.7V, 2000-3500mAh, 500 cycles, $3-5 → Best budget option
🔋 LiFePO4: 3.2V, 1000-3000mAh, 2000+ cycles, $8-12 → Longest life, safest
🔋 Lead-Acid (Sealed): 12V, 1.2-7Ah, 300 cycles, $10-20 → High power needs
🔋 NiMH: 1.2V, 1000-2500mAh, 500 cycles, $2-3 → Cold weather, low power

💡 Key Insight:

LiFePO4 lasts 4x longer than Li-ion (2000+ cycles vs 500 cycles). For a sensor waking every 15 minutes, LiFePO4 will last 5-10 years.

        🌟 Best for IoT Sensors:
        Budget: Li-ion 18650 ($3-5) - works well, common
Long life: LiFePO4 ($8-12) - 2000+ cycles, safer
High power: Lead-Acid ($10-20) - for pumps, valves

    

🔋 Battery Capacity Calculation

Formula: Capacity (mAh) = Daily consumption × Days of autonomy

Example: Soil sensor waking every 15 minutes
- Daily consumption: 24mAh
- Desired backup: 7 days (rainy season)
- Required: 24 × 7 = 168mAh
- ✅ 18650 (2600mAh) = 15x margin

Example: Weather station (1 min wake)
- Daily consumption: 360mAh
- Required for 3 days: 1080mAh
- ✅ 18650 (2600mAh) works fine

🔋 18650 Battery Basics

Voltage: 3.7V nominal (full: 4.2V, empty: 2.8V)
Protected vs Unprotected: Protected has over-discharge protection (recommended)
Capacities: 2000mAh, 2600mAh, 3000mAh, 3500mAh
Trusted brands: Samsung, LG, Panasonic, Sony
⚠️ AVOID: "Ultrafire", "Trustfire" - fake capacities, dangerous

💡 Battery Life Examples:

2600mAh + 15 min wake → 108 days (without solar)
2600mAh + 5 min wake → 36 days (without solar)
2600mAh + 1 min wake → 7 days (without solar)
With solar (2W panel) → Indefinite (recharges daily)

⚠️ Critical Lithium Battery Safety:

❌ Never discharge below 2.5V (permanent damage)
❌ Never charge above 4.2V (fire risk)
✅ Always use protection circuit (TP4056, etc.)
✅ Use fire-proof container for charging
✅ Don't expose to heat > 60°C (leave in sun)

🎯 Key Takeaways:

✅ LiFePO4 = longest life (2000+ cycles)
✅ 18650 = best value ($3-5)
🔋 Capacity needed = daily mAh × backup days
⚠️ Always use protected cells + TP4056

💡 Key Takeaways:

Apply these concepts directly to your farm or project.
Take notes on important details for the quiz.
Use the button below to track your progress.

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