Is there a way to determine the charging current available?
Try CurrentWidget.

It's a widget that you can configure to show not only the current but also the temperature and voltage.

If that doesn't work (as what seems to be the case with modern devices), Ampere is worth a look. From the XDA post, the Moto X 2014 is supported - I'm not sure if you have that model, though.

Also, from the app thread:


  If your Lollipop device (or later) shows 0 all the time: There are Lollipop devices which don't have a working power profile (the new Lollipop interface to get the measured current). But on some of them is the old interface still present and maybe also working. Please use the settings option "Old measurement method" in this case. You can force the app with it to use the old interface, if the Lollipop device has at least one. Maybe it helps...