The heart of any portable electronics project is its power supply. Choosing the wrong battery can lead to burnt-out components, short runtimes, or even safety hazards. In this guide, we break down the three most common rechargeable battery chemistries used by makers today: Li-Ion, LiPo, and LiFePO4.
1. Lithium-Ion (Li-Ion)
The workhorse of the modern world. If you've ever held an 18650 cell, you're familiar with Lithium-Ion technology. They are cylindrical, robust, and offer excellent energy density.
Key Characteristics:
- Nominal Voltage: 3.6V - 3.7V
- Max Voltage: 4.2V
- Common Form Factor: 18650, 21700 Cylindrical Cells
- Safety: Moderate. Can vent with flame if abused.
Best For: Projects requiring long battery life in a rigid enclosure, such as Bluetooth speakers, flashlights, and power banks.
2. Lithium Polymer (LiPo)
LiPos are the performance kings. They use a polymer electrolyte which allows them to be made in flexible pouch shapes. Their main advantage is their incredible Discharge Rate (C-Rating), allowing them to dump massive amounts of current instantly.
Key Characteristics:
- Nominal Voltage: 3.7V
- Max Voltage: 4.2V
- Common Form Factor: Soft flat pouches
- Safety: Low. Vulnerable to physical damage and overcharging.
Best For: High-performance applications like Drones, RC Cars, and wearable tech where weight and shape factor are critical.
⚠️ Safety Warning
LiPo batteries are sensitive. Never puncture them, over-discharge them below 3.0V per cell, or leave them charging unattended. Always use a balanced charger.
3. Lithium Iron Phosphate (LiFePO4)
The safest of the bunch. LiFePO4 batteries sacrifice a bit of energy density for extreme durability and safety. They are chemically stable and have a completely different voltage curve.
Key Characteristics:
- Nominal Voltage: 3.2V
- Max Voltage: 3.65V
- Cycle Life: 2000+ cycles (vs ~500 for Li-Ion)
- Safety: High. Extremely stable and resistant to thermal runaway.
Best For: Solar power storage, remote IoT stations, and projects where safety and longevity are more important than size.
Comparison at a Glance
| Chemistry | Voltage (Nominal) | Cycle Life | Cost | Safety |
|---|---|---|---|---|
| Li-Ion | 3.7 V | 300 - 500 | Low | Medium |
| LiPo | 3.7 V | 300 - 500 | Medium | Low (Careful!) |
| LiFePO4 | 3.2 V | 2000+ | High | High |
🚀 Summary & Recommendation
For most beginner projects like a custom GameBoy or sensor node, stick with 18650 Li-Ion cells; they are cheap, easy to find holders for, and reasonably safe. If you are building a drone, you need LiPo. For a solar-powered weather station that needs to run for 5 years? LiFePO4 is your best friend.