monitoring DC (low) voltage?

Has anyone done any work on monitoring DC voltage?

I have a small bank of batteries I charge via solar panels and use to power lights etc in our summer house and garden. 

Ideally I'd like a node that can measure the DC voltage of the 12v battery bank. Is this possible? Has it been done before?

Robert Wall's picture

Re: monitoring DC (low) voltage?

It has been done many times. Try a search.

Ian Eagland's picture

Re: monitoring DC (low) voltage?

This might help

I am using a derivative of this to monitor current and voltage of my DC solar system and posting to my emoncms.



jb79's picture

Re: monitoring DC (low) voltage?


DC voltages can be measured by this simple function:


Udc = analogRead(A0);


This will give you a value from 0-1023, if your arduino is running on 5V, you have to do this:

Udc = analogRead(A0)*5/1023;

Reading the other analog ports: A1-A5


If you add a voltage divider, you will have to multiply the reading with another factor depending on the resistors.


If you want to monitor voltage and current, I'm using such a system (.ino file included in the zip file):


best regards


Robert Wall's picture

Re: monitoring DC (low) voltage?

The key question is: Is your DC supply that you want to measure earth referenced or floating, or referenced to another voltage? If your battery negative is at the same potential as the emonTx GND, or it is floating so that it can be connected, there's no problem. If it's referenced to another voltage, things get very messy and you need a means of isolation somewhere along the line - either at the analogue input or in the programmer/usb link to your computer.

warlock's picture

Re: monitoring DC (low) voltage?

If I just wanted to monitor the battery voltage would this work ?


Robert Wall's picture

Re: monitoring DC (low) voltage?

Probably. bearing in mind all the comments above.

warlock's picture

Re: monitoring DC (low) voltage?

JetJackson's picture

Re: monitoring DC (low) voltage?

Hmmm.. There is some good stuff here chaps but this is still all quite new to me so its a bit of a steep hill to climb.


Ideally I would like to understand how to build something that I could connect to a group of batteries and it post back the voltage of each battery to emoncms as an input so I can store it in a feed, and then in a dashboard. A bit like the emonTH does with the voltage of the AA batteries.

pb66's picture

Re: monitoring DC (low) voltage?

There are several threads on dc voltage sensing and battery monitoring, a bit more info may be needed for specific assistance but you could take a look at this thread Monitoring battery voltages.

how many batteries? how are they connected? what voltage are they? the questions posed by Robert, 5 posts back are all important factors in deciding on what you need. If you are not sure of the specifics then just describe your set up.



Comment viewing options

Select your preferred way to display the comments and click "Save settings" to activate your changes.