If you have a voltage meter hook it up to the terminals. A fully charged battery will usually measure around 12.4-12.6. Anything under 12 will no longer hold a full charge. To test the alternator measure the voltage while the car is at idle with no accessories on. It should be around 13.5. Then turn some stuff on like lights, a/c, and rev it up and take a measurement. The reading should either go up to 14ish or drop slightly and return to 13.6. If either of those happen that means the alternator is properly adjusting the load. If it drops to like 12.8 and never goes back up you might have a bad alternator.