Frequently Asked Questions

How do I power Wattmon?
Wattmon is powered directly from any battery bank between 6 and 48v DC.  The device comes with a cable and lugs.  You can also power the device from any wall power adapter within this voltage range, for example when monitoring higher voltage battery banks.

Is it a linux based system?
No, Wattmon runs WattmonOS which is our proprietary real time operating system based on FreeRTOS. It is designed specifically with the features required, making it light weight.  The entire kernel fits in less than 400kb.

Does it run PHP?
Wattmon contains a built-in scripting language called uPHP, which is compatible with the PHP syntax to make it easy for anyone with web programming experience to be able to create add ons.  It does have limitations but hence the 'micro' prefix.

Can I use it to monitor temperature?
Yes, Wattmon has a onewire bus, and can interface with multiple DS18b20 temperature sensors

Can I interface this with 3rd party devices?
If your device supports Modbus RTU over rs485, you can easily write a driver descriptor file and let Wattmon automatically poll your device.

Can I interface this with my existing inverter?
If your inverter has a serial port, you can (with some programming knowledge) create a script to communicate via the internal serial port. Depending on the model, you may need to insert a level shifter and open the top cover to reach the pin header, so this is not an out of the box solution, but it is possible.

What is the latency when responding to actions?
Wattmon runs through the internal action queue 20 times per second, and can switch on or off a device at that time.  However, the total time it takes for the command to trigger a relay to be switched will depend on the modbus speed, and the number of devices.  Although command messages are given priority, it can take up to one second to trigger devices.

How many devices can I connect to one Wattmon?
You can connect up to 8 unique types of device at the same time.  However, if the devices are all of the same type (one type of power meter, for example) then up to 20 devices can be connected.  The main issue with multiple devices is the limited memory inside Wattmon.

Where is my data stored?
All your data is stored on the microSD card, which can handle up to three years of log files without a problem, since it is 8 GB. We are also working on a cloud storage solution that will be subscription based with monthly fees for people with multiple installations.

What kind of warranty do you provide?
Wattmon comes with a 1 year warranty which covers manufacturing defects and any issue apart from the following:
- lightning damage
- incorrect power supply (overvoltage)
- physical damage

Why would I choose your product over X?
That's a difficult one to answer.  However, one of the things Wattmon does well is provide an easy way for non programmers to create simple automation and act on data collected from the system.  This is something unique, and Wattmon aims to make data logging and control available to the consumer and not just to technicians.  In addition, everything is easily modifiable and programmable via a web browser without the need for custom software, making it easy to remotely upgrade and add functionality.  It is flexible enough to be adaptable to monitor esteem solar, wind, and much more. We could go on, but these few features seem noteworthy.

How can I get the CSV data?

The /logs/[YEAR]/[MONTH]/ folder contains a daily CSV entry with the date and 1-minute interval.  The first column is the unix timestamp (seconds since 1/1/1970) and can be converted in excel or OpenOffice using the following formula:

The columns differ depending on what is selected for data logging.  See the Data Collection page in Wattmon to identify the various column headers - they are in the same order as show there.

I lost connectivity to my Wattmon, how do I get back in?

This could be due to several reasons.  If you have simply forgotten your IP address, you can press and hold the reset button for just over 5 seconds until the script light stops flashing.  The device will then reboot and the IP address will be reset to  Alternatively, you can remove the SD card and put it in your PC - edit the /config/network.ini file and enter the desired IP address.

If your device seems unresponsive and you suspect a firmware corruption (it stopped right after the last firmware update) then press and hold the reset button while you apply power to the device.  You should see the script light flashing quickly.  Release the reset button and wait for it to boot up.   If this does not work the firmware hex file may be corrupt.  In this case, download the firmware from, unzip the contents and copy the image.hex file to the root of the SD card.  Then repeat the process of pressing the reboot button while powering up the device.