energy tester

If you want to test batteries and transformers separately under load (such as finding out if a battery is charged up or in good condition, etc) then you are probably after a battery load tester (or similar).

If you are after just checking current (A) with the batteries and transformers connected up to an existing load, then you are after either an ammeter (basic unit), clip-on ammeter (allows you to measure current without having to disconnect the wires) or multimeter (almost all have a built-in ammeter function and can also measure voltage and other useful things).

Try a basic google search for "battery load tester", "ammeter" and "multimeter". Wikipedia probably has some good information to help you get started in choosing exactly what you need.