Batteries and Cells
Battery chemistry, types (Li-ion, LiPo, NiMH, Lead-Acid), characteristics, advantages and disadvantages for robotics
Batteries and Cells
Batteries are the lifeblood of mobile robots. Choosing the right battery type is critical for performance, runtime, weight, and safety. Understanding battery chemistry helps make informed decisions.
Battery Chemistry Fundamentals
How Batteries Work
A battery converts chemical energy into electrical energy through oxidation-reduction (redox) reactions:
Negative terminal (−): Oxidation (electrons released)
Electrolyte: Ions flow inside battery
Positive terminal (+): Reduction (electrons accepted)
External circuit: Electrons flow to power loadKey Parameters
| Parameter | Unit | Description |
|---|---|---|
| Voltage (V) | Volt | Electrical pressure |
| Capacity (mAh/Ah) | Amp-hour | Charge stored |
| Energy (Wh) | Watt-hour | Total usable energy |
| C-rating | Times | Discharge rate |
| Self-discharge | %/month | Charge loss over time |
| Cycle life | Cycles | How many times rechargeable |
Example Battery Rating
12V 5000mAh 50C Li-ion
12V = Nominal voltage
5000mAh = 5 Amp-hour capacity
50C = Can discharge at 50 × 5A = 250A peak!Battery Chemistry Types
Battery Comparison Chart
Cell Configuration
Series vs Parallel
Series connection (voltage addition):
+5V cell | +5V cell | +5V cell
↓ ↓
+15V total
Capacity = single cell capacity
Current capability = single cell capabilityParallel connection (capacity addition):
+5V cell ┐
+5V cell ├→ +5V total
+5V cell ┘
Capacity = 3× single cell
Current capability = 3× single cellExample: 3S2P Battery Pack
3S = 3 cells in series (3 × 3.7V = 11.1V)
2P = 2 parallel groups
[Cell] ─ [Cell] ─ [Cell]
║ ║ ║
[Cell] ─ [Cell] ─ [Cell]
↓
11.1V, 2× capacity, 2× current capabilitySummary
Battery Chemistry Quick Reference:
| Type | Voltage | Capacity | Power | Cost | Cycles | Best For |
|---|---|---|---|---|---|---|
| LiPo | 3.7V/cell | High | Very High | High | 300-500 | Drones, racers |
| Li-ion | 3.6V/cell | High | Medium | Medium | 1000+ | Mobile robots |
| NiMH | 1.2V/cell | Medium | Low | Low | 1000 | Budget bots |
| Lead-Acid | 2V/cell | Medium | High | Very Low | 200-300 | Heavy stationary |
Selection Guide:
✓ Choose LiPo if: High power, light weight, accept fire risk ✓ Choose Li-ion if: Long runtime, safety important, can afford weight ✓ Choose NiMH if: Budget limited, casual use ✓ Choose Lead-Acid if: Very heavy loads, stationary application
How is this guide?