---
id: edge-car-tracker
area: edge
level: 3
title: "Artefact — Vehicle tracker on LTE Cat-M"
claim: "A tracker that sleeps between reports · wakes on a schedule or when the car moves · and reports when it leaves a boundary set from the web interface."
confidence: in-progress
period: "2024–"
tech: [ESP32, LTE Cat-M, NB-IoT, SIM7080G, GPS, LiFePO4]
metrics: [{label: "battery packs", value: 2}]
artefacts: []
public: true
last_verified: 2026-10-28
tags: [edge, tracker, lte, low-power, artefact]
---

The build is on the bench: two LiFePO batteries, a buck converter, an ESP32 with GPS, and a
cellular module for the uplink. The car keeps the packs charged while it is running.

![Waveshare Pico SIM7080G Cat-M and NB-IoT module — the cellular link in the tracker. Product image, used to identify the part.](../../assets/images/sim7080g-module.jpg)

## What it does

Two behaviours, chosen by the settings rather than hard-coded. When the car is parked the
ESP32 sits in deep sleep, wakes on a timer, checks its own configuration, and reports only
what the settings ask for. When the car is moving it stays awake and reports on a shorter
interval. Either way the interval and the boundary can be changed from the web interface,
and a change can force an immediate update rather than waiting for the next wake.

The geofence is the part that matters. A boundary is drawn from the web interface, and the
device is responsible for deciding whether it has left it — which is why the settings have
to travel to the device rather than live only in the server.

## Why LTE Cat-M rather than WiFi

The tracker lives in a car. WiFi coverage is a driveway, not a road. Cat-M and NB-IoT were
chosen because they are designed for exactly this shape of traffic — small payloads, long
sleeps, coverage beyond what 4G handsets need — and because the modules are cheap enough to
leave installed.

## What it proves

A complete path rather than a demo: constrained hardware, a power budget that dictates the
schedule, a device that holds enough state to act on its own, and a web application that
configures it and shows where it has been.

## Still open

Field testing across the full battery cycle. The sleep interval that is right for a parked
car and the interval that is right for a moving one are guesses until the discharge curve
has been measured over a week rather than a day.