OverviewHistoryStatsSecurity
npx skills add ...
Documentation
SKILL.md
npx skills add wedsamuel1230/arduino-skills --skill battery-selector
Helps choose the right battery type and charging solution for Arduino/ESP32/RP2040 projects. Use when user asks about battery options, charging circuits, power source selection, or says "what battery should I use". Covers chemistry selection, safety, voltage regulation, and charging circuits.
npx skills add wedsamuel1230/arduino-skills --skill battery-selector
Guides battery chemistry and charging circuit selection for embedded projects.
This skill includes bundled tools and references:
Interactive selection:
Command line:
| Chemistry | Voltage | Rechargeable | Energy Density | Cost | Safety |
|---|---|---|---|---|---|
| Alkaline | 1.5V/cell | No | Medium | Low | Very safe |
| Lithium Primary | 3V | No | High | Medium | Safe |
| NiMH | 1.2V/cell | Yes | Medium | Medium | Safe |
| LiPo/Li-ion | 3.7V | Yes | Very High | Medium | ⚠️ Needs care |
| LiFePO4 | 3.2V | Yes | High | High | Safer than LiPo |
| Lead-acid | 2V/cell | Yes | Low | Low | ⚠️ Acid hazard |
Pros:
Cons:
Best For:
Voltage Configurations:
Pros:
Cons:
Best For:
Charging:
Pros:
Cons:
Best For:
Critical Safety Rules:
Pros:
Cons:
Best For:
Pros:
Cons:
Best For:
Current Limits:
Single LiPo → 3.3V:
LiPo → 5V:
⚠️ Get module WITH protection (6 pins, not 4 pins)
Premium solution with:
Example:
| Project Type | Best Battery | Capacity | Charger |
|---|---|---|---|
| Simple Arduino | 4x AA | 2500mAh | None |
| ESP32 portable | 18650 | 2600mAh | TP4056 |
| Wearable | Small LiPo | 500mAh | TP4056 |
| Robot | 2S LiPo | 2200mAh | Balance |
| Ultra-low power | CR2032 | 220mAh | None |
| Solar project | LiFePO4 | 3200mAh | MPPT |
Use the shared Arduino skill contract: state assumptions, required tools and versions, implementation steps, tests/evidence by proof stage, known limitations, and recovery/security notes.
START
│
▼
Is project rechargeable? ──No──► Alkaline/Lithium Primary
│ (Disposable batteries)
Yes
│
▼
What voltage does MCU need?
│
├── 5V ──► LiPo + Boost converter
│ OR 3x/4x NiMH
│
├── 3.3V ──► Single LiPo (3.0-4.2V)
│ Directly compatible!
│
└── 12V+ ──► Multi-cell LiPo pack
OR Lead-acid
│
▼
How much current?
│
├── <50mA ──► Small LiPo (500-1000mAh)
│ OR Coin cell (CR2032)
│
├── 50-500mA ──► Standard LiPo (1000-3000mAh)
│ OR 18650 cells
│
└── >500mA ──► Large LiPo (3000mAh+)
OR Multiple 18650s
External power recommendedCells Voltage Use With
────────────────────────────
2x AA 3.0V 3.3V MCUs (with LDO)
3x AA 4.5V 5V MCUs (direct or LDO)
4x AA 6.0V 5V MCUs (with regulator)
9V 9.0V With 5V/3.3V regulator✅ DO:
- Use protected cells with BMS
- Store at 40-60% charge
- Use proper TP4056/similar charger
- Monitor temperature during charge
- Use battery with JST-PH connector (prevents polarity swap)
❌ DON'T:
- Puncture, crush, or bend
- Charge below 0°C
- Discharge below 3.0V
- Leave charging unattended (first few times)
- Use damaged/puffy batteriesContinuous: <2mA
Pulse: <15mA (brief)
DON'T use for: WiFi, Bluetooth, motors, LEDsLiPo outputs 3.0-4.2V
Most 3.3V MCUs tolerate this range directly!
Option 1: Direct connection (if MCU allows)
LiPo(+) → 3.3V/VIN pin
Option 2: LDO for clean 3.3V
LiPo(+) → [AMS1117-3.3] → 3.3V pin
(Need 4V min input for AMS1117)
Better: Use HT7333 LDO (low dropout, low quiescent)
Works from 3.3V input!Option 1: Boost converter
LiPo(+) → [MT3608] → 5V → VIN pin
Option 2: PowerBoost module (Adafruit)
Includes charging + boost + protection
Option 3: USB power bank
Already regulated 5V + charging built-in┌─────────────────────────────┐
│ TP4056 with Protection │
│ │
│ [USB-C] ─► [TP4056] ─► [DW01+FS8205] ─► [B+/B-]
│ IN Charger Protection To Battery
│ │
│ Features: │
│ - 1A max charge current │
│ - Overcharge protection │
│ - Overdischarge protect │
│ - Short circuit protect │
│ - LED charge indicator │
└─────────────────────────────┘
Wiring:
B+ → LiPo positive
B- → LiPo negative
OUT+ → Load/MCU positive
OUT- → Load/MCU negative❌ Never charge LiPo with a constant voltage supply
❌ Never charge LiPo with a phone charger directly
❌ Never charge at >1C rate (e.g., 1000mAh → max 1A)
❌ Never charge frozen batteriesStep 1: Determine average current (from power-budget-calculator)
I_avg = _____ mA
Step 2: Determine required runtime
T_required = _____ hours
Step 3: Calculate minimum capacity
C_min = I_avg × T_required × 1.25 (safety factor)
C_min = _____ × _____ × 1.25
C_min = _____ mAh
Step 4: Select battery
Choose capacity ≥ C_min
Consider: size, weight, form factorProject: Weather station
I_avg: 15mA
T_required: 48 hours (2 days between charges)
C_min = 15 × 48 × 1.25 = 900mAh
Selection: 1000mAh LiPo (gives ~67 hours actual)❌ "My 9V adapter should work"
LiPo needs CC-CV charging at 4.2V max!
✅ Use TP4056 or dedicated LiPo charger❌ Draining LiPo below 3.0V
Permanently damages the cell!
✅ Use protection module OR monitor in code:
if (batteryVoltage < 3.2) {
enterDeepSleep(); // Protect battery
}❌ Battery can't handle WiFi TX spike (500mA)
Causes brownout/reset
✅ Add 100-470µF capacitor near MCU
✅ Size battery for peak current, not just average❌ Swapping battery wires = magic smoke
✅ Use JST-PH connectors (keyed)
✅ Add protection diode or P-FETBattery: 18650 (3000mAh) or LiPo 2000mAh
MCU: ESP32 with deep sleep
Charger: TP4056 with protection
Runtime: Weeks to monthsBattery: LiPo 1000-2000mAh flat pack
MCU: Any
Charger: PowerBoost or TP4056 + boost
Runtime: Hours to daysBattery: 2S or 3S LiPo pack (7.4V or 11.1V)
Regulator: Buck converter to 5V
Charger: Balance charger (external)
Runtime: Minutes to hoursBattery: CR2032 or 2x AA
MCU: ESP32-C3 or ATtiny with deep sleep
No charger needed
Runtime: Months to years