---
title: "Calculating Battery Life Using the µA-Level Current Measurement Tool NRF-PPK2"
url: "https://maker.wiznet.io/TheoIm/projects/calculating-battery-life-using-the-a-level-current-measurement-tool-nrf-ppk2/"
markdown_url: "https://maker.wiznet.io/TheoIm/projects/calculating-battery-life-using-the-a-level-current-measurement-tool-nrf-ppk2/md"
type: "UCC: User Created Content"
author: "화양연화"
author_url: "https://blog.naver.com/khc3544/224106260613"
editor: "WIZnet"
editor_url: "https://maker.wiznet.io/"
original_author: "화양연화"
original_url: "https://blog.naver.com/khc3544/224106260613"
published: "2025-12-18"
language: "en"
likes: 0
views: 458
comments: 0
source: "WIZnet Makers (https://maker.wiznet.io/)"
---

# Calculating Battery Life Using the µA-Level Current Measurement Tool NRF-PPK2

> Calculating Battery Life Using the µA-Level Current Measurement Tool NRF-PPK2

Original author: 화양연화 (source: https://blog.naver.com/khc3544/224106260613)

## Article

## Battery Life Calculator: Precision IoT System Design with NRF-PPK2

### Project Overview: Why Precision Current Measurement Matters

For IoT sensor systems deployed in the field, especially in **hard-to-reach environments like underwater pressure sensors**, the critical question is: "How long will the battery last?" Traditional rule-of-thumb calculations fall short because:

- Actual current consumption ≠ Datasheet specifications

- Sleep mode leakage currents are overlooked

- Wake-up peak currents are missed

**NRF-PPK2 (Power Profiler Kit 2)** is Nordic Semiconductor's current measurement tool that measures from **nA (nano-ampere) to over 1A** in real-time and automatically calculates **charge consumption (mC)**.

---

### System Architecture: Underwater Pressure Sensor + LoRa + MQTT Gateway

#### Overall System Design

```plaintext
[Underwater Environment]
    │
    ▼
────────────┐
│  Underwater Module       │
│  ──────────  │
│  • ATmega328P (→88)    │
│  • MS5837 Pressure         │
│  • RS485 TX                       │
│  • Battery: 3xAA                │
└────┬──────┘
            │ RS485
            ▼
┌──────────┐
│  LoRa TX Module          │
│  ────────     │
│  • ATmega324PA         │
│  • MS5837 (Barometer)│
│  • LoRa 930MHz, 10mW │
│  • TPL5110 Timer          │
│  • Battery: 12xAA          │
└────┬──────┘
            │ LoRa (Wireless)
            ▼
┌────────────┐
│  Control Room Gateway    │
│  ──────────     │
│  • ESP32 (ESP-NOW)         │
│  • W5500 (Ethernet)           │
│  • LoRa RX                           │
│  • MQTT Broker Link          │
└────────────┘
```

![](https://maker.wiznet.io/upload/ckeditor5/624672600%5F1766140072%2Epng)

![](https://maker.wiznet.io/upload/ckeditor5/624672600%5F1766140644%2Epng)

![](https://maker.wiznet.io/upload/ckeditor5/624672600%5F1766140662%2Epng)

**Operation Cycle:**

1. TPL5110 timer wakes system every 6min 15sec (standby: tens of nA)

2. LoRa module powers on underwater module

3. Underwater module measures pressure/temp → RS485 transmission

4. LoRa module measures barometric pressure + integrates data → LoRa TX

5. Immediately enters sleep mode

---

### ESP32 + W5500 MQTT Gateway Board

The developer designed a custom **slot card expansion board** for stable IoT gateway operation.

#### Hardware Configuration

![](https://maker.wiznet.io/upload/ckeditor5/624672600%5F1766140021%2Epng)

![](https://maker.wiznet.io/upload/ckeditor5/624672600%5F1766140048%2Epng)

https://blog.naver.com/khc3544/223645195375?trackingCode=blog_bloghome_searchlist

#### Design Features

**1. Power Management Improvement**

- Initial: 12V direct supply → 7805 overheating

- Improved: DC-DC step-down to 8V then 7805 → minimal heat

**2. W5500 Heat Mitigation**

- Problem: 2x W5500 on single AMS1117-3.3V → 60°C

- Solution: Added 9×9×12mm aluminum heatsinks

**3. Firmware Update Simplification**

```plaintext
Rear header on slot card:
[GND] [VCC] [TX] [RX]
    ↓
Connect FT232RL USB-Serial
    ↓
Hold Prog button → Press Reset → Programming mode
```

**4. Expandability**

- Standalone use: External W5500 via slot pins

- LoRa module: E-byte LoRa mountable on each card
  - M0, M1 pins: Tied to GND (pre-configuration required)
  - Aux pin: For transmission feedback (5sec timeout without)

---

### Measurement Results Analysis

#### 1. Wake-up Cycle Charge Consumption

**Measured Values:**

![](https://maker.wiznet.io/upload/ckeditor5/624672600%5F1766140263%2Epng)

```plaintext
Window Selection: Wake-up period only (~2 seconds)
Total Charge: 19.02 mC (milli-coulombs)
 Window Selection: Full cycle (6min 15sec)
Total Charge: 19.02 mC (same!)
```

**Meaning:** Negligible charge consumption during sleep (thanks to TPL5110's tens-of-nA standby)

#### 2. Sleep Mode Average Current

![](https://maker.wiznet.io/upload/ckeditor5/624672600%5F1766140286%2Epng)

```plaintext
Average Current: 0.17 µA (micro-ampere)
```

**Comparison:**

- ESP32 Deep Sleep: ~10 µA

- ATmega328P Power-down: ~0.1 µA

- TPL5110 Standby: Tens of nA

→ This system's sleep current is **nearly perfect**

---

### Battery Life Calculation

#### Formulas

```plaintext
1. Average Current:
   I_avg = Q_cycle / T_cycle
 2. Battery Life:
   T_survive = C_bat / I_avg
```

#### Actual Calculation

**Input Values:**

```plaintext
Q_cycle = 19.02 mC (charge per cycle)
T_cycle = 6min 15sec = 375 seconds
C_bat = 1,300 mAh × 4 banks = 5,200 mAh
```

**ChatGPT Result:**

```plaintext
Step 1: Average Current
I_avg = 19.02 mC / 375 sec
     = 0.0507 mC/s
     = 0.0507 mA
     = 50.7 µA
 Step 2: Battery Lifetime
T_survive = 5,200 mAh / 0.0507 mA
          = 102,564 hours
          = 4,273 days
          = 11.7 years
```

**Conclusion:** 12x AA batteries (4 banks) enable **approximately 11.7 years** of operation!

---

### Practical Tips: Using NRF-PPK2

#### 1. Measurement Mode Selection

**Source Meter Mode (Power Supply + Measurement)**

- Voltage range: 0.8V ~ 5V

- Max current: 1A

- Advantage: No external battery needed

**Ampere Meter Mode (Measurement Only)**

- External battery required

- Voltage range: 0.8V ~ 5.5V

- Advantage: Reflects actual battery characteristics

#### 2. Window Setup (Charge Calculation)

```plaintext
PPK2 Software:
1. Start data collection
2. Mouse drag to select measurement range
3. Auto-calculation:
   - Average Current
   - Max Current
   - Total Charge (mC)
```

#### 3. Important Considerations

**Voltage Drop Check:**

- Initial battery voltage vs end-of-life voltage

- Verify system minimum operating voltage

**Environmental Variables:**

- Temperature: Battery capacity varies (drops sharply below 0°C)

- Aging: Consider 20% capacity reduction in real operation

---

### Circuit Design Reference

#### Underwater Measurement Module

![](https://maker.wiznet.io/upload/ckeditor5/624672600%5F1766140366%2Epng)

```plaintext
ATmega328P (→ Switching to ATmega88)
    │
    ├─ I2C → MS5837 (Pressure/Temperature)
    ├─ UART → RS485 Transceiver (MAX485)
    └─ Power → 3xAA Series
 Critical: Epoxy molding inside PVC pipe required!
```

#### LoRa Transmission Module

![](https://maker.wiznet.io/upload/ckeditor5/624672600%5F1766140391%2Epng)

```plaintext
ATmega324PA (2x Hardware UART)
    │
    ├─ I2C → MS5837 (Barometric pressure)
    ├─ UART1 → RS485 RX (underwater module)
    ├─ UART2 → LoRa Module (E-byte E32)
    └─ EN → TPL5110 Done Pin
 TPL5110 (Timer)
    │
    ├─ DRV → System Power MOSFET Gate
    ├─ DELAY → Resistor sets period (6min 15sec)
    └─ DONE ← ATmega completion signal
```

---

### Final System Specifications

**Power Consumption:**

- Wake-up: 19.02 mC (2 seconds)

- Sleep: 0.17 µA

- Average: 50.7 µA

**Battery Life:**

- 12xAA (5,200mAh): 11.7 years

- 18xAA (7,800mAh): 17.5 years

**Communication Range:**

- LoRa 930MHz: ~1-3km (with obstacles)

- MQTT via Ethernet: Unlimited (with internet)

---

Source: https://maker.wiznet.io/TheoIm/projects/calculating-battery-life-using-the-a-level-current-measurement-tool-nrf-ppk2/