Car lights flicker and radio dies, then car dies....

Not without testing , hooking up a scan tool an checking for stored DTC'S - diagnostic trouble code's . The battery lasting only a day or so is because the alternator isn't charging it . That's what the battery light on is telling your.
You don't say what make , model an year vehicle it is ? Your best bet , take it to a qualified repair shop. Most vehicles the alternator is controlled by the PCM/ECM - engine computer . Just replacing parts isn't going to fix it .

Diagnosing Common Automotive Charging System Problems

www.onallcylinders.com/.../diagnosing-some-common-charging-system-...

Sep 18, 2013 - Flickering gauges. ... Problem: The charge indicator light flickers while driving. .... My alternator has been replaced for the third time in 5 months. ... I bought a new regulator but it is still doing the same thing... .... my headlights wont turn on, car runs fine when jumped, battery last for maybe 3 hours, any ideas ...

All lights Flickering/Pulsating only when motor is running ...

www.cadillacforums.com/forums/cadillac-forum/t-221843.html

Feb 11, 2011 - So i have noticed for a while now that all my interior lighting (radio, tach, even ... Installed the battery and have not had issues starting since then. ... So now ipurchased a new alternator "just in case" figuring i would eliminate the .... Interior lights and headlights still seem to pulse/flicker while idling the most, ...

Lights Flickered. Replaced Alternator. Now more flicker? - Camaro ...

www.camarozone.com/.../lights-flickered-replaced-alternator-now-more-...

Apr 22, 2013 - 20 posts - ‎4 authors

It could be a couple things. Take it to a shop or a place like auto zone and have them test the alternator and the battery, its free :) If they both are testing as good, the next thing would be to check the battery terminals and connections. It simply is not getting the enough charge back to the battery for one reason or another.

thats correct it suposed to do that thats how it charges the battery if the ignition lights flicker make sure that the wire lomb in the back of alternator is pressed in correctley was it a new audi part or an after market one as i have had many problems with after market parts for my mercedes so if i can afford them i stick with them hope this helps ivan ps there is also a relay that sends current to the battery not sure where that is but it determans when to send voltage to battery to keep it charged

Is the Alternator charging. Could have a short drainning battery also. Check fuses.

it does sound like the alternator but i would get the battery charged and then have someone to check the charging system and the fuses......get the battery charged first so they want try to sell you a battery and an alt. cause there are a few people out there that want to take you.....

seems like you need an alternator try charging your battery star the engine and take off negative cable if engine dies it's your alternator. did you have an alternator light on in the dash

It sounds like the Alternator is actually bad.
One great way to determine this:
Recharge the new battery with a trickle charge overnight. Make sure use remove the wires going to the Battery before recharging.
Replace the Battery Wires.
Get the Vehicle Started.
When it has Started: Leave it Running and Disconnect and Remove the Negative side of the Battery. If the Vehicle dies, it is the Alternator that is bad, and needs to be replaced..
The Battery starts that vehicle, and provides nominal power to certain accessories. The Alternator actual Runs the Engine and Recharges the Battery with a low trickled charge.

Sounds like a charging system issue. Just because the alternator itself tested fine doesn't mean it's getting power to the car and battery. Charge the battery and start the car (with everything connected normally, including alternator). While car is idling, disconnect the battery (negative post wI'll do). If car dies, there's a problem with the alternator wiring/harness. Once the vehicle is running, the alternator should provide plenty of power. Check voltage at battery (from alternator) and should be around 14V. Check alternator fuse.
Could be the voltage regulator in the alternator going out, which would need a new alternator.

Battery failed.Or alternator problem.Recharge the battery then try..If red light is sill on when car is running then the alternator needs replacing