Monitor your Car Battery Remotely using ESP8266

Having the ability to monitor your car battery can prevent some unpleasant surprises. In this video, I'll show you how I assembled the hardware, loaded the software and installed it in my car. You will need a Wemos D1 mini, its power shield and some resistors. First, I started by removing the power plug. I installed the smaller connector to make the hardware more compact. The d1 mini can measure external voltage up to 3.3 volts by using a voltage divider using these are values, which brings it within that 0 to 1 volt the ADC can tolerate. To increase the 3.3 to 16 volts, needed for the car battery, we need to increase our 1.44 for MegaOhm. To do that, we can add another 1.22 MegaOhm in series to get the total 1.4 4 MegaOhm. I did this by soldering a 1 MegaOhm resistor to a 220 KOhm resistor. I added shrink wrap and then connected one end to the voltage input from the car and the other end to a zero as shown here. I then connected the d1 mini to my laptop to load the software. Make sure you pick the sensor bin version for the analog input functionality. I even resumed with the typical Tasmota setup. Before heading to the car, I attach a long wire to the power input terminals to be able to connect them to the car battery. At the car, I opened the hood and located the fuse box. I found the fuse box to be a safe and secure place to install my device. I first wrapped the device with heat resistant tape to cover any exposed pins. You need this kind of tape to stand the engine heat. Since the entire car's chassis is ground I found the nearest screw and connected my ground to it. I then located the nearest connection to the battery positive rail and connected my positive power input to it I then proceeded by calibrating the range of the analog input. I did this by connected a multimeter to the battery and read the current voltage- in my case it was 12.73. To adjust the range I used the AdcParam command. I then did some trial and error until my reading was close to 12.73. Now it was time to close the fuse box and the car hood. Back in home assistant, I opened the configuration file and added a new mqtt sensor - the code is in the description below. After I saved, I restarted home assistant for it to take effect. When it came back online, I added the new sensor to the dashboard. Now you can use the sensor to trigger any kind of automation. I have it setup so it sends me an alert when the voltage drops below 12. I hope you found this video useful. Thank you for watching .... and I'll see you in the next one

Channel: MrDIY

Views: 20,130

Keywords: esp8266, wemos, wesmo d1mini, wemos d1, wemos mini, home assistant, hassos, MQTT, car battery, monitor car battery, power shield, resistors, 3.3v, 12v, 14v, home automation, car, wifi, wireless, 16v, automation, gitlab, tasmota, tamotizer, stayhome, esp8266 projects, monitor a 12 v battery, smart 12v battery, car battery monitor

Id: VnGRFwDrLHo

Length: 6min 34sec (394 seconds)

Published: Tue Jun 02 2020

Reddit Comments

[u/letmetryallthat]

I built this to keep an eye on the car battery in these COVID19 times. This could also be used to monitor solar setup or any 12V battery system.

I placed the project files, schematics and code on Instructables: https://www.instructables.com/id/DIY-Monitor-Your-Car-Battery-Code-Setup

[u/jokerbone]

Just a thought - would it not be possible to do this via one of the cigarette lighter power points within the car?

[u/nico282]

Any measurements on the current absorption of the device? That should be pretty low compared to the capacity of the battery, but if the car stays parked for weeks it could significantly reduce battery life.

[u/catalintabirca]

No deepsleep? It will help deplete the battery faster.

[u/TechGuy219]

I’ve been wanting to start a project for something like this but I’d like to have some control over the car perhaps and more information than battery level.

I’m curious if anyone has figured a way to hook maybe a raspberry pi to the car and get readings from various sensors? For example I have a 2017 Lincoln MKZ Hybrid, would be nice to have things like the fuel readings, oil life, lock & remote start control (all available in the Lincoln app) but have it all integrated to my home. Could be used as a presence sensor as well, just a few ideas I have but I’m sure the creative minds out there can think of more

[u/BlackReddition]

Thanks for the write up, I’ve already got my motorbike battery charging itself automatically, this would add some much needed stats on how quickly it depletes and could trigger my charger. I’ll definitely be adding a fuse between this and the battery and I think it needs a housing too for protection.

[u/hkrob]

Brave man restart HA without checking configuration first!!

[u/5c044]

You may well find that calibration is non linear, especially since you use a very high value resistor. The resistance introduced by the adc may vary a bit depending on voltage. Did you check calibration at low end of range needed?

Are you using deep sleep to minimise drain from d1 mini? Probably only need to do readings every hour or so.

[u/Jugrnot]

Shit.. this is a spectacular idea!