ESP8266 Keeps An Eye On Your Batteries

There are many more things to know about a battery than its voltage and current output at any given moment, and most of them can’t be measured with a standard multimeter unless you also stand there for a long time with an Excel spreadsheet. The most useful information is battery capacity, which can tell you how much time is left until the battery is fully charged or fully discharged. [TJ] set out to create a battery data harvester, and used the ubiquitous ESP8266 to make a fully-featured battery monitor.

Measuring battery capacity is pretty straightforward but it does take time. A battery is first benchmarked to find its ideal capacity, and then future voltage and current readings can be taken and compared to the benchmark test to determine the present capacity of the battery. The ESP8266 is a relatively good choice for this kind of work. Its WiFi connection allows it to report its information to a server which will store the data and make it available for the user to see.

The first page of this project details building the actual module, and the second page outlines how to get that module to communicate with the server. Once you’ve built all of this, you can use it to monitor your whole-house UPS backup system or the battery in your solar-powered truck. There is quite a bit of information available on the project site for recreating the build yourself, and there’s also a video below which shows its operation.

8 thoughts on “ESP8266 Keeps An Eye On Your Batteries

  1. Like it. WiFi-enabled projects are often battery powered anyway so if you could get the ESP8266 to handle both the battery monitoring as well as requirements of the project it’s supporting then that would be very cool indeed.

  2. the esp8266 is
    very cool, as we
    all know. its good
    to see more projects
    using it.

    but I have a question
    about the esp8266
    projects page. or, not
    really a question, but
    more of a comment
    or observation:


  3. The capacity of a battery does NOT tell you how much time is left until a battery is fully charged or discharged, the state of charge does! The capacity tells you how much energy a battery can discharge whenever it’s fully charged. Please stop writing stupid things like this …

    1. Even if you keep track of the current going in and out of the battery like a modern day laptop battery pack, you can only get rough guesstimate of the the remaining battery life. You’ll need to know the battery voltage, temperature too. This is a problem that had been worked on by engineers in the last 30 or so years. Not likely be solved that easily.

      google for “Coulomb counter” “fuel gauge”on the topic.

      1. Bit of an obvious statement really, you can’t accurately predict remaining battery life without an exact knowledge of your project’s future energy requirements up until the point the battery is drained. If you know that then the profile between any two consecutive cycles will be fairly close, in which case this project will be very accurate so long as you actively monitor it and adapt your model accordingly (which is exactly what this project is designed to do). And if you don’t know it, well, at least this is better than the alternative!

      2. Maxim market a range of devices (MAX17041 for example) which do ‘gauging’ based purely on battery voltage and (optional) temperature. You have to model your battery pack, but these work quite well. They are also quite a bit cheaper than coulomb counting.
        [No connection with Maxim, just used this part on projects.]

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