DIY Battery Monitor - ESP32 based

[Techstyle]

Thanks, Jason. Until I saw this, I was going to install a free-standing PZEM-015 battery monitor down below at the nav station. However, after seeing your video, I realized that your concept is a much better monitoring solution as I'll be able to conveniently see my battery status on any device screen along with OpenCPN, Grafana outputs etc.

The size of your shunt concerns me. How did you determine that this is the size which you require? The PZEM-015 uses a 300A shunt which, based on Victron's shunt, is apparently even smaller than commonly used.

You may be correct and I will run some testing when on the boat, but the Shunt I am using is based on a 50mV drop at 100A, meaning that at 300A it would be 150mV, I read the one you were looking at was 75mV at 300A (half the drop).  The max current draw is when the engine is cranking, I will do some testing at this but it would normally split between all three batteries, unless you are cranking on just your start battery. It could be useful to double up (put 2) shunt resistors for the start battery, which would make the same size as the one you specify.

but the reason I want to keep it small is that I believe most of the time, my current draw is <10amps, which would be 5mV for the 100A shunt and 2.5mV for the 200A (or your 300A/75mV) - that's not a lot

---

- other functions - the Batteries on my 336 are in the rear lazarettes.  also in the area is the black water tank and fuel tank - I will be trying to add external black water level sensing, as well as seeing if I can grab the fuel level without interfering with the analogue gauge

Thanks Jason, very nice development!
I am also working to sense diesel tank level. To do that (without interference with gauge reading) I plan to measure el voltage on the signal terminal of the gauge with an I2C ADS115. I shall measure signal voltage at different tank levels and build data in SENSESP "CurveInterpolator" . Rest of code will be similar to temperature reading.

Thanks, I am going to do the same with the INA219 and also build a lookup curve like you suggest, the only thing that concerns me is I may need to know the input voltage and don't want to run a wire all the way to the helm(gauge).  however, I think I can use the battery voltage from one of the other batteries.

my build is moving along quite quick, I am looking at contact-less sensors for the black water tank to determine the level (https://www.aliexpress.us/item/2251832778905166.html), there will be 4 or 5 of them at different heights and then some calcs for level.