Battery Monitor, Solar, Shunts

[Mistroma]

If you have an existing shunt then an ESP32/8266 works well with an INA219 current sensor, just piggy backed across the existing shunt and use a clamp meter to calibrate it. The INA219 is a few quid on ebay or even better design a PCB from JLCPCB with everything already soldered on. Little project for someone
Adafruit INA219 Current Sensor Breakout
Seems to be accurate down to about 100/200mA.

I was considering DIY a couple of years ago but the eBay unit made it pointless. All the data via LCD or Bluetooth and no shunt needed for under £20. I would buy another if mine failed but they seem to have vanished (at least cheap, non-shunt, Bluetooth variety).

My plan would now be to salvage the sensor and use ESP32 if the eBay unit ever failed. Next step would be ESP32 with shunt if the sensor had also failed. I replaced my main multi-display unit with a couple of Arduinos and a pair of ADS1115s and that's worked well so far for V,A, fuel and water. It has worked well but didn't give sufficient detail at the batteries (where I see solar, alternator,mains charging and windlass), hence the eBay unit.

 

[Mistroma]

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[lw395]

It's very useful to know the current your fridge draws.
It's even more useful to know how that averages out, how many Ah per day.

So, a lot of people find the Nasa battery monitors helpful and good value, even if the SOC info is dubious, hard to calibrate etc.

The big thing to keep in mind is that all these toys are supposed to provide you with useful info. So what is the info and how are you going to make use of it?
We use Ah info to help make decisions, like we've used 20Ah already today so we'll need to get some charge in if we want to run the fridge tomorrow.
It's easy to gather a lot of numbers which you end up making no use of.