What is causing my car battery light to come on and inside lights start to flicker?

Noticed sometimes after turning engine off, nothing happens as in car wont start. Mechanic computer checked car and found something stuck (whatever the hell that means). Car worked for about a week and then battery light came back on, inside lights flicker.|||That may be a faulty alternator. Take your car to an auto parts store and have them check your electrical system. Most places will do it for free.|||Probably a short in the electrical system. He says its stuck cause he prob isnt getting a return signal back when he does the check.|||Make sure your battery cables are on tight.|||cut your radio off all times|||If you are driving an older model it could be the boards in the computer are breaking down, this will interupt the signal return because of the sensitivity to temperature change.|||When the red battery light comes on, that means your battery's not staying charged up like it should be. One reason could be that your battery's over 4 years old and needs replacing. If you haven't bought a new battery in the last 4 years, buy a new one. When they install the new battery, have them check the alternator charging voltage with a digital voltmeter. It should read about 14.5 Volts depending on the temperature and charge state of the battery.