Looking to monitor the 12v battery level

B01M9IKYVH on amazon

Brought it over from my last car. When tested on my old car it was within 0.3v of what I tested at the battery with a multimeter. Close enough.

Want to know what the 12v is resting at? Before you turn the car fully on at the start of a new day, start it in accessory mode. Read the gauge on the cig port charger. That's roughly what the battery is resting at. Then you can start the car fully with the brake pedal and of course it'll go between 12.x to 14.x volts depending on how much it needs from the HV battery.

This is an easily solution with no modifying of anything that is accurate enough for most people. If you want to know how much is lost in travel to the cig port then start the car in accessory mode, make note of the cig port charger, then go test the battery at the terminals. That will tell you how much difference there is. Adjust for that in your head when you read the cig charger value.

 

That's good to know. I am familar with columb counting (using shunt resistor) and bttery voltage data gathering in Battery Monitor Systems for LFP battery solar systems.They work well.
Does this device use shunt resistor or hall effect device ?

 

Or install and use a Battery Monitor BM2 BM3 Bluetooth 4.0 Wireless Battery Tester 12V Automotive Battery Load Tester,Automotive Charging and Cranking System Monitor Digital Battery Analyzer for Android & iOS.
It's just a battery voltage monitor that stores battery voltage over time and can be viewed using bluetooth on your other devcies (phone). Data can be downloaded for lastt month. It claims to do much more, but it's just a battery voltage recorder. About $30 and easy to install right on the battery terminals.

PS: I used a cigarett lighter voltage meter in my pickup. It works to answer the question, is the battery at a voltage that indicates charging in progrss. Not at all precise, but performs the function I need there.
BT-2's are going into all my wheicles now.

 

Nothing wrong with that. Different possible solutions. I like mine because it gives me some old style usb ports, is a known reliable readout from my use of it on my last vehicle, and it makes use of what was otherwise going to be an empty cig lighter port. Oh, and there's no additional idle drain like there is with the bluetooth one since the cig port doesn't get power if the car is off. No app to bother with either.

 

The BT-1 or 2 or three has a very low perasitic current draw. Nearly none.

Specifications:
Input Voltage: 6V-20V
Average Current: 1.5mA
Operating Temperature -40 to 90℃
Bluetooth Range: 10 Meter
Product Dimensions: 5.5 x 3.5 x 1.6cm
Voltage Accuracy: (9-16V) ± 0.03V
Bluetooth Name: Battery Monitor
App Keyword: BM2

 

I bought and am using this cigarett lighter accesory in my truck since January. Upgrade from my old battery voltage accessory used for years in that truck.
Amazon B0C33M8NJ8