My gear
https://www.prospectingaustralia.com/forum/img/member-images/1932/1568981012_batterycheck-app.jpg
https://www.prospectingaustralia.com/forum/img/member-images/1932/1568981012_bm_pro.jpg
All of the negative - cables both load and charge go through the Block on the battery. It's basically a 100A shunt, with a bluetooth Tx. The + fly lead (the one with the + on it) has 3 wires, 1 is the + power for the devices blutooth etc, the other 2 are for the temperature pickup in the + terminal.
I then have an App on my Android ph. It instantly shows the present voltage of the battery, this will vary depending on SOC or if under charge. As all - wires go through this, the Amps are a resultant of all loads and charge. BTW I can isolate all loads and all charge independently.
The way I use it is turn off loads and it reads a + number of charge amps. Turn off all charge and it shows the load total. Turn on both charge and loads and it calculates if a charge or discharge situation is happening, how long the battery will last at that rate and the battery temp.
Best thing I've ever bought, no holes to drill, bolt onto the battery at one end and the other replicates the battery terminal. Install the App and pair.
BTW BM pro is mine, the App pic is from their web site. As I've never seen my battery at that temp, lol.