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Battery monitors typically show:
In general, the monitor will watch for your system to hit a configured 100% state of charge voltage and start counting amps used while below that voltage. This is an imperfect science with lead batteries because 100% SoC is only valid after a complete charge, and because different discharge rates will change the effective capacity.
Note: Watching amps trail off at the end of lead Absorption (endAmps) will also tell you when the bank is fully charged. The battery manufacturer will specify something like C/200 or C/100 as a sign Absorption is complete.
One benefit of having a shunt-based monitor over a charge controller monitor is the shunt can discern between [dis]charging vs [dis]charging+loads.
Meters typically need a few settings defined:
The most famous battery monitor is the Bogart Tri-Metric TM-2030 series.
This monitor will interface and operate their SX-2030 solar charge controller. The monitor will still provide amp-counting and other metrics when used on it's own.
For folks who are [dis]charging at 50A/75A, a cheaper shunt is available for 1/5th the price of a Bogart.
Heavier-duty shunts are available (up to at least 350A).