wedsamuel1230/arduino-skills/battery-selector

uv run --no-project scripts/compare_batteries.py --interactive

# Find battery for 50mA project, 24h runtime
uv run --no-project scripts/compare_batteries.py --current 50 --hours 24
 
# Require rechargeable
uv run --no-project scripts/compare_batteries.py --current 100 --hours 12 --rechargeable
 
# List all batteries in database
uv run --no-project scripts/compare_batteries.py --list

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 recommended

Cells   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 batteries

Continuous: <2mA
Pulse: <15mA (brief)
 
DON'T use for: WiFi, Bluetooth, motors, LEDs

LiPo 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 batteries

Step 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 factor

Project: 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-FET

Battery: 18650 (3000mAh) or LiPo 2000mAh
MCU: ESP32 with deep sleep
Charger: TP4056 with protection
Runtime: Weeks to months

Battery: LiPo 1000-2000mAh flat pack
MCU: Any
Charger: PowerBoost or TP4056 + boost
Runtime: Hours to days

Battery: 2S or 3S LiPo pack (7.4V or 11.1V)
Regulator: Buck converter to 5V
Charger: Balance charger (external)
Runtime: Minutes to hours

Battery: CR2032 or 2x AA
MCU: ESP32-C3 or ATtiny with deep sleep
No charger needed
Runtime: Months to years