On Ebay there are modules that read both voltage (0-30V) and current (0-10A) or (0-100A).
I've done a lot of dry camping
and the 2 things that are critical are battery
drain current (did you leave something on), and solar panel
current to recharge the battery
. Also it is nice to know battery
voltage accurately as it is an indication of state of charge.
I ordered a couple of these modules (under $5 with free shipping), and they are perfect for the job. They are best used with a push button so they do not introduce a constant drain (mine draws 16ma. Measured), but when you want to know, just push the button. The internal current shunt is in the ground line and is 0.007ohms so costs nothing in terms of power loss.
There is no data sheet when delivered, but lots of data if you Google YB27VA. Simple to hook up: thick black to source -ve (battery or solar), thick red and thin red to both source and load +ve through push button, and thick yellow to load -ve.
Sent from my iPad using Fiberglass RV