Device to measure 12v Battery

Hardware
1

Trying to find a device to measure the voltage of a 12v battery which I use to start my generator. The generator / battery is in a shed in a remote location and is charged by a small solar panel.

I’d like the device to be powered by the battery as it is sending its data back to HA via either wifi or Bluetooth. It would work much like a temperature sensor, except we’re logging volts vs. temperature readings.

Any suggestions?

2

DIY?

There are a number of ESPHome components you could use. I use both of these:

1 Like
3

No suggestions, but I do have a hint.

Search for ADC in Esphome

4

Yeah if all you want is the voltage and not current & power as well a simple resistive voltage divider and the ADC will do.

Also for powering the ESP device from 12V there are many DC-DC buck modules, search for “XL4015”.

ELEC-STEPDOWN-XL4015-V2-02
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5

You can use Shelly Uni for this: https://www.shelly.com/products/shelly-plus-uni

It can be powered directly from the battery, then use Shelly integration in HA.

Here, you have docs: https://kb.shelly.cloud/knowledge-base/shelly-plus-uni

6

I use an ESP8266 based on https://community.home-assistant.io/t/monitor-your-car-battery-in-home-assistant/201508/71 to monitor a Clarke 1010 Jump Starter. It’s been working for years with no problem.

7

Juras or anyone -

Very interested in the Shelly Uni Plus solution.

Realize that I’m a “zero” when it comes to electronics.

Was looking at the Shelly Uni schematic and have questions:

  • Would the 12v go to pins 3 & 7 (IN)?
  • Don’t I need 5v going to pins 6 & 7 (IN)?
  • Without a separate power source, don’t I need to transform the 12v to 5v to supply the 5v above?
  • Once I get this wired, and set up the Shelly integration, HA should track the 12v very similar to a temperature module - correct?

Thanks for any help.

8

Shelly Uni Plus can be powered in many ways.

In your situation, you power it from the battery you are going to measure AND in order to actually measure the battery’s voltage, you also need to connect it to the proper input.

In your situation, I assume you power it with 12V from the battery(1 and 2), and also to (3 and 7).

This Shelly can also be powered using 5V, like USB, but in your situation you can simply use direct battery feed.

Measure voltage will be visible in the WebUI and of course in HA.

9

So just to be quite clear, we’re talking about the Shelly Uni PLUS, correct?
And wiring, you’re suggesting:

  • the positive of the 12v battery directly to pins 1 & 3?
  • the negative of the 12v battery directly to pins 2 & 7?

Sorry that I’m so in the dark!

10

1 OR 2 is “+” for powering the Shelly.
3 is “+” for measurement.
7 is “-” for powering the Shelly(it is common GND).

So from battery “+” to 1 OR 2 AND 3.
From battery “-” to 7.

I have this Shelly, so I might be able to verify it, maybe tomorrow.

@ I have checked and it works as expected. The battery I have measured is in bad shape. Meter showed 9.51V and Shelly measured 9.49V, so not that bad.

Screenshot_20241031_065303_Firefox
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@ Using pins 1 OR 2 AND 7(GND) for powering is good because it doesn’t have to be constant but must be within specified range (9-28V), at least to my understanding. So in your situation the range might be like 12-15V(no charging/charging).

@ I have edited info about using pins after some more digging.

11

Hey, thanks so much Juras. I wired pos from batt to 1 & 3 - and neg from batt to 7 and it worked like a charm.

For anyone else’s benefit:
To connect to your Shelly device, connect your device to the Wi-Fi network with a name(SSID) like shelly1 - 84CCA87D??? . Use the universal IP address for all Shelly devices - 192.168. 33.1 to access your device’s Web Interface, where you can set a Wi-fi network for the Shelly uni to connect to.