To tell how many amps a battery is capable of, you have to load test it, which (ironically) drains part of the battery. What you probably want to look for is the mAh (milliamp hour) rating for yours for an idea of strength. A simple google search should bring that up. Every battery monitor app I've seen only shows the voltage level, which does drop during use. I think those may also pull from what the phone itself reports and don't read it independently.
If you're having drain issues, it could be the battery going bad if it's old, or you maybe have some apps that have background services working. A good example would be a weather reporting widget that access the net (a big power drain in itself) often to keep conditions updated.