DC Voltage measurement

Does anybody know of a way to measure voltage of my 48v battery bank? i would like to be able set up scenes to turn on my electric water heater and electric car charging when the battery bank exceeds a certain voltage. Electric water heating is already controlled by ewelink manually but I would like to automate it. Any suggestions ? Thankyou


I also have a well-automated solar system with some devices connected to the ewelink and I really need to measure the dc voltage because then it would be much easier to use based on the voltage of the batteries and not the hours of the day

Buy the Digital Voltage Control Relay Module, then you need to modify a smart door sensor that you will connect to the contacts of the relay module. Look here for such a module https://vi.aliexpress.com/item/32977883482.html?gatewayAdapt=glo2vnm
I have described the modification of the door sensor in this topic
Trigger a device ( if lamp is offline) - #12 by euv

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Thanks for your reply. Your system would certainly work well for an on/off situation but what I am looking for is a voltage level sensor. for example if the battery pack voltage gets up to say 50 VDC then the electric water heater would cut in and if the thermostat in the water heater was up to temperature the battery voltage would continue to rise to say 50.5 VDC which would then turn on the electric car charger

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I have wondered if anyone has ever connected a different type of one wire sensor to a TH16 or similar? I could use a one wire ADC perhaps

And you have the water heater on and off. That’s exactly what you want to be able to adjust according to the voltage to turn on the electric water heater. The module from aliexpress does exactly that. You will push the module when the voltage reaches 50V, then the contact of the module will turn on, and as soon as it turns on, it will also turn on the door sensor, and then you will create a scene and connect the other devices, thermostats, chargers… For another option, I don’t know if there will be a little more with voltage control.

Yes I see what you are saying. A bit more hardware but it would work. Thanks that’s an option

You can connect a Sonoff POW which measures voltage, power, and current. If you want to DIY, you can simply use a ZMPT101B module (costs about $1.50) or if you really want to build your own then just get the ZMPT101B current transformer. You can then use a data bridge program like Node Red to get the data and automate the response depending on whatever criteria you want

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You can look here for a barebones method:

Although it is initially for AC voltage, you can adapt it for DC by removing the 1N4007 diode.

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This is a great suggestion, I hope the person asking has that kind of skills and time.

I to would just use an Aruino. They have built in Analogue-to-digital converters and some have wifi built in. Then you could just add a voltage divider using school level physics, as I doubt it can handle 50V. There is a Reference pin but the default is 5V (I think). Also think the advised power is 5-12V for most arduino but the maximum is more, although not your 50V. Pretty sure the upper limit is 20V but not sure on the lower limit.
Then just with a purchase of an Arduino, two resistors and a USB power bank you have what you want on-line. Not sure how you’d integrate it with Sonoff though; I’d ask them. My guess is there’s a docker that you could install on an iHost.

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