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RV Battery Monitor

This project will monitor RV batteries while it is in storage.

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Have you ever forgot to turn your batteries off in your RV and they went dead? This project will read the voltage of both of the RV house batteries as well as the engine starting battery and send the data hourly to ThingSpeak. An email message will be sent as an alert when the battery drops below a set voltage. The project will run from a dedicated power pack.

The "RV Battery Monitor" uses a ESP-01 and a ADS1115-4-Channel-16-Bit-I2C to read the voltage of up to 4 batteries.  Battery voltages are uploaded hourly the ThingSpeak for storage and graphing.  An alert email is also sent hourly if any of the  battery voltages drops below a set value, in my case 12.4 volts. 

Graphs can be seen here: https://thingspeak.com/channels/870224

ino - 8.36 kB - 09/19/2019 at 12:27

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RV Battery Monitor.sch

Eagle CAD schematic

sch - 444.96 kB - 09/30/2019 at 15:22

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RV Battery Monitor.brd

Eagle CAD board

brd - 67.20 kB - 09/30/2019 at 15:22

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  • 1 × ESP-01
  • 1 × ADS1115-4-Channel-16-Bit-I2C
  • 1 × LD1117 3.3
  • 1 × 10uF capacitor
  • 3 × 10M resistor

View all 10 components

  • 1
    Step 1

    I used the "CircuitSetup Solderable Breadboard" and mounted the ESP-01 on a 2x4 header.  It is easily removable for programming.

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Discussions

Karl-Wilhelm Wacker wrote 09/12/2019 at 20:15 point

same as my earlier comment about the FETs - the circuit will bias itself off when the ESP8266 is off

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Karl-Wilhelm Wacker wrote 08/26/2019 at 15:53 point

Use a P-type FET like the IRLML6402 as a hi side switch - tie the source to the voltage you wish to monitor, the drain to the resistor divider and a pair of 10K or so resistors - one between the gate and source to bias it off, and the other between the gate and the drain of a 2n7000 fet, with the 2n7000 source tied to ground, and the gate to 2  resistors, a 10k to ground, and a 1K to the micro pin that goes high to enable the divider.

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rockfishon wrote 08/26/2019 at 16:43 point

Thanks for the idea.  I am now thinking of using very high value resisters to reduce the current flow and just leave them connected all of the time.  Something like 500k and 100k.  That should draw 25uA if I calculated correctly, which is nothing to a large 12v battery.  I think that will work since the input impedance of the ads1115 is many meg ohm.

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Karl-Wilhelm Wacker wrote 08/26/2019 at 16:46 point

Don't forget a cap 0.1uf ceramic across the lower resistor for noise suppression and to handle the current draw of the ADC during the conversion cycle.

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rockfishon wrote 08/23/2019 at 11:41 point

I am trying to figure out how to engage a voltage divider so that it is not always drawing current while the ESP8266 is in deep sleep.

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TheGrim wrote 09/23/2019 at 20:17 point

Look at this project. I build this with kids at the library. Control the bottom of the divider with a NPN transistor to disconnect ground when you want to do so. 

http://rsg-electronics.com/wp-content/uploads/2019/08/NightLight_006.pdf

Basically interrupt the path of the current at the bottom of the divider and only engage it when you need to do so.

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