Monitor the vehicle's electrical system via app

Remote access requires a network interface on the bus. It connects to the on-board network bus as a normal participant, integrates into the router via network cable or WLAN, and provides data to the corresponding app. Without this interface, the on-board network remains limited to the system monitor.

What is required

Three things need to come together. First, a functional on-board network bus with the participants whose values you want to see — the app displays nothing that is not measured. Second, the network interface. Third, a network where the interface and end device meet: on board or in the vehicle, usually a small router that is already available for mobile communication or shore connection.

The interface supports both ways to the network — wired via Ethernet and wirelessly via WLAN. The wired option is less conspicuous: no reception problems in the metal casing, no re-connection after a router restart. Where a cable cannot be laid, WLAN will do, but with consideration for where the interface is mounted.

NoteThe app itself is free. Ongoing costs only arise for the internet connection if you want to access it from afar — in the local network, access also works without it.

Local or remote

Two scenarios that should be distinguished. Local means: the phone or tablet is on the same network as the interface. This works without the internet and is the normal case on board — the app becomes a second, mobile monitor.

Remote means: The vehicle or boat is connected to the internet via mobile communication or shore connection, and you are looking from afar. This is the function for which most people install the interface in the first place — and the one with the most preconditions: The router must run continuously, the connection must be stable, and the system must not be without power.

Don't forget the power balance

Remote monitoring means continuous operation. System monitor, network interface, and router run around the clock, each with a small but constant consumption. In the order of a few hundred milliamperes, this adds up to a two-digit ampere-hour number over a month.

It follows that anyone who wants to monitor in winter storage needs either shore power, a solar system that covers the quiescent consumption, or a battery bank that is designed accordingly. The contradiction of wanting to switch everything off and still see how the battery is doing cannot be resolved.

WarningMonitoring that itself drains the battery is worse than no monitoring at all. Before winter storage, the quiescent current of the entire chain must be measured — not estimated.

Recording and analysis

Remote monitoring becomes interesting less through the instantaneous value than through the trend. The network interface records measured values on a memory card; some system monitors can also do this. From these recordings, questions can be answered that a glance at the current voltage does not reveal.

• Does the battery bank really reach the charge termination voltage at the end of a charging cycle, or does the regulator stop beforehand?
• How deep does the discharge go overnight — and how does that change over the season?
• Does solar yield cover daily consumption, or does each day deplete the reserve a little?
• Is there a consumer running that shouldn't be?

These questions also form the bridge to troubleshooting: A sporadic error that never occurs when standing next to it becomes visible in the recorded trend.

Integrating third-party devices

The network interface has additional interfaces through which devices not connected to the on-board network bus can be connected — a serial interface for inverter-chargers via their adapter, and two connections for battery buses of lithium systems with their own management system.

The benefit is clear: charger, battery management, and on-board network appear in the same view instead of requiring three apps and two displays. Before purchasing, it is nevertheless worth checking whether the specific third-party device is supported — the protocols are manufacturer-specific and change with firmware versions.

Securing access

A device that is remotely accessible must be secured. The essentials are unspectacular and effective: change default passwords on the router and all involved devices, operate the WLAN with its own, unguessable key, keep firmware up to date, and do not set up port forwardings whose purpose you cannot explain.

Typical errors

• Interface without measurement technology. The app only shows what shunts and interfaces provide. No state of charge without a battery shunt.
• Quiescent current underestimated. Continuous operation of monitor, interface, and router for weeks is not trivial.
• Router overlooked as a weak point. If it fails, monitoring is gone — and you usually don't notice.
• WLAN through metal. An interface deep in the control cabinet rarely has good reception.
• Default passwords left unchanged. The most common error with any networked device.
• Only instantaneous values considered. The trend answers the questions that matter.