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DataHub: How to View Battery and Alternator Data

View live NMEA 2000 battery and alternator data on a DataHub or DataHub Pro, whether you're on or off the boat.

Written by Matt Crockett

Victron Cerbo connected to a DataHub Pro via NMEA2000 / N2K

Monitor your boat's battery and alternator onboard or remotely by connecting them to the DataHub via your NMEA2000/N2K network.

While both the DataHub and DataHub Pro can show the same values in the DataHub > Services > NMEA > DC page, only the DataHub Pro can also show battery SOH % (State of Health) or SOC % (State of Charge) on your PredictWind GPS Tracking page when you have a PredictWind Standard subscription or higher.

Example of MV Bliss with 6 battery instances providing different compatible data sets for GPS Tracking

Before you start

You need:

  • DataHub or DataHub Pro running firmware 4.54 or later.

  • Battery or alternative data available to N2K from compatible external equipment.

  • A working NMEA 2000 connection between the source equipment and DataHub.

What DataHub does

DataHub receives and displays battery and alternator monitoring data produced by equipment such as:

  • A Victron Cerbo and its connected battery monitor, shunt or BMS.

  • A compatible NMEA 2000 battery monitor.

  • An alternator or charging-system device that transmits DC status.

The DataHub then presents that information locally in its web interface. It does not calculate State of Charge or State of Health from voltage alone.

Where to view NMEA > DC Battery and Alternator Status

  1. Connect your phone, tablet or computer to DataHub Wi-Fi or a DataHub LAN port.

  2. Open Safari or Chrome and go to 10.10.10.1.

  3. Log in using your DataHub administrator credentials.

  4. Under Services, select NMEA.

  5. Select the DC page on the top menu.

What you can expect to see for Battery Health

Each detected DC source is shown with its identity, instance and available values. The live Victron example shows:

  • Name: House Battery 1

  • Manufacturer: Victron Energy

  • Model: System battery

  • Version: 1.0

  • Instance: 239

  • Voltage: 13.92 V

  • Current: -1.2 A

  • Temperature: NA

  • State of Charge: 100%

  • State of Health: 92%

  • Time Remaining: 240.0 hours

  • Ripple Voltage: NA

  • Amp Hours Used: 0.0 Ah

Which DC values can be displayed?

Information

Local DC page

DataHub Pro GPS Tracking

Name

Yes, when supplied

No

Manufacturer

Yes

No

Model

Yes

No

Version

Yes

No

DC instance

Yes

No

Voltage

Yes

Yes

Current

Yes

Yes

Temperature

Yes

Yes

State of Charge

Yes

Yes

State of Health

Yes

Yes

Time Remaining

Yes

No

Ripple Voltage

Yes

No

Amp Hours Used

Yes

No

An alternator is presented as a DC source. DataHub displays the values transmitted for that source. Battery-specific fields may remain unavailable for an alternator.

Compatible NMEA 2000 sentences - PGN 126992, PGN 127506 and PGN 127508

The following PGNs are the main sources for DC information:

PGN

Name

Information used by DataHub

126996

Product Information

Manufacturer, model, version and product identity

127506

DC Detailed Status

DC type, instance, State of Charge, State of Health, Time Remaining and Ripple Voltage

127508

Battery Status

Battery instance, voltage, current and temperature

Data for the same battery must use matching DC and Battery instances so that the related fields can be presented from a single source.

Using a Victron Cerbo as the source

A Victron Cerbo can make supported battery and charging data from connected Victron equipment available on NMEA 2000. DataHub then displays the fields the Cerbo and its connected equipment transmit.

The available values depend on the installed battery monitor, shunt, BMS and sensors. For example:

  • A battery monitor may provide voltage, current, State of Charge and Time Remaining.

  • State of Health can remain NA when the source does not calculate or transmit it.

  • Ripple Voltage and Amp Hours Used may not be supplied by every system.

  • Other values may remain NA where no values are supplied, or values are provided in a proprietary format.

The instance number is assigned by the source equipment. DataHub displays it so different DC sources can be identified.

Monitoring several battery banks

DataHub uses the NMEA DC or Battery instance to distinguish sources such as:

  • House battery bank.

  • Engine starter battery.

  • Generator starter battery.

  • Bow-thruster battery.

  • Auxiliary battery bank.

  • Alternator or another charging source.

Each source should use a unique instance. Duplicate instances can cause incorrect display in the DataHub and on your GPS Tracking page.

View battery data on GPS Tracking through the DataHub

This remote view is available for DataHub Pro only and requires a PredictWind Standard subscription or higher.

Open your PredictWind GPS Tracking page and expand Boat Data. The available battery fields are:

  • Battery Voltage, for example 13.9 V.

  • Battery Current, for example 5.6 A.

  • State of Charge, for example 96%.

  • State of Health, for example 89%.

The local DC page can contain more detail than GPS Tracking. Temperature, Time Remaining, Ripple Voltage and Amp Hours Used are not shown in the GPS Tracking battery section.

What do NA, - and negative current mean?

NA means DataHub does not currently have a usable value for that field. A common reason is that the source identifies the battery but does not transmit that measurement.

Why does GPS Tracking show -?

A dash means that no value is available for that battery field on GPS Tracking.

First, check Services > NMEA > DC on the DataHub:

  • If the local value is also unavailable, check the source device and NMEA data path.

  • If the local value is valid, check the GPS Tracking service, subscription and upload path.

A populated local page proves DataHub Pro is receiving the source value. It does not prove that the value has been uploaded and displayed remotely.

Does negative current mean discharge?

DataHub displays a signed current value received from the source. Check the source manufacturer's sign convention before interpreting charge and discharge direction.

Current limitations

  • DataHub and DataHub Pro do not replace a battery monitor, shunt, BMS, engine gateway, alternator regulator or equipment protection system.

  • Available values depend on what the external equipment transmits.

  • DataHub Pro GPS Tracking shows only voltage, current, State of Charge and State of Health.

  • The general DC page is for monitoring. It does not configure or control the source equipment.

  • The displayed data does not provide a configurable battery alarm.

Why is no battery or alternator displayed on my GPS Tracking page?

If you connect the devices to the DataHub and do not see the expected data in the DataHub or on your GPS Tracking, check the below:

  1. On your GPS Tracking page, click on Boat Data > More to see Battery and Alternator data.

  2. Confirm that the source equipment is powered and displays valid data on its own interface.

  3. Confirm it is configured to transmit the required NMEA data.

  4. Confirm it is connected to the same NMEA 2000 network as DataHub.

  5. Confirm DataHub > Services > NMEA is configured to use the correct Source: NMEA2000 on CAN0.

  6. Reopen Services > NMEA > DC.

A valid value on the source equipment proves that it measured the value. It does not prove that the value is being transmitted to or received by DataHub.

Why are some values present and others missing?

Different source devices provide different fields. A voltage sensor may provide only voltage, while a shunt or BMS can also provide current, State of Charge, temperature or Time Remaining.

Missing optional information does not necessarily mean the NMEA connection has failed.

Why are values assigned to the wrong bank?

Check the instances configured by the source equipment. Each battery bank and DC source should use a distinct instance.

If two sources use the same instance, correct the source configuration using the manufacturer's interface or an appropriate NMEA 2000 configuration tool.

What should I send PredictWind Support?

If your boat or alternator instrument data is not displayed either in the DataHub or on your GPS Tracking page, enable Remote Access and include:

  • DataHub or DataHub Pro model.

  • DataHub firmware version.

  • Selected NMEA source and connection method.

  • Source equipment manufacturer, model and firmware.

  • Screenshot of the source equipment showing the expected values.

  • Full screenshot of Services > NMEA > DC.

  • Full screenshot of Services > NMEA > Engine, when relevant.

  • Displayed DC or Battery instances.

  • GPS Tracking screenshot and selected time, when the issue is remote display.

  • A clear description of which values are correct, missing or assigned to the wrong source.

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