No start or no crank. no radio no radio ,power locks ,headlights or brakes light.

Starter motor solenoid

You folks never learn, you can't use just any aftermarket sound system in these newer vehicles. The electronics are all networked together. I have no idea what you have damaged.

You need to get you alternator tested, it sounds like the current output is too low.

Assuming you have checked all fuses, the next step would be to locate central grounding points (there may be several) and remove and clean battery terminals and the remote ends of the cables at their attachment points.Locating some of these may be easier with a manual covering the electrical system of the car:
Sebring manual
When removing battery cables, always start with the negative cable first and reattaching it last.

what lights? headlights? dash lights? I would check the connections. If its the starter usually you will hear a heavy "click" when you turn the key.

I had the same problem too..My battery was stone dead..My lights were on but their probably isnt enough cranking amps to start the truck...I would take the battery out and charge it overnight and then try to crank it in the morning...i just changed the battery and the truck started right up

If the battery is dead, the ignition keys will not come out of the ignition cylinder. Don't force the ignition key to ensure you do not damage the pass lock system in your ignition. Jump the battery or replace it to get enough voltage to remove the key's from the ignition and check the fuse box for any blown fuses. Good luck and keep me posted.

check to make sure yu have 12v at the battery, once you do turn the ignition to start, if nothing, check the fuse and relays that control ignition, if all is good then the click sound is coming from the starter, have the solenoid replace.

haveyou checked you fuesable link wich is on the fire wall in the engine compartment it will be a red wire comming off of a sidwase dimond shaped block

power loss.
any good car elect. tech find this pronto.
just takes a volt meter to find the voltage drop point.

top fails:
1: corroded fuse box on right front finder (under fuse box)
2: did you say it kills motor too. cant figure above.

what about heater fan, it uses tons of current.
as does HL followed by tails.

20amps, 15amps and 5amps respectively

you have resistance some where.
and load , kills the voltage .

for me.
i'd:
check battery voltage , when it dims out.
then of ok 12.5v is ok key on,not started.
then check voltages at a right fender , fuse panel
all points there, 12.5vdc , same as battery v.
if OK
then
check voltage at the fuse above right knee
with load full, hl, fan, brakes, just key on.

now you know what circuit is fail ing by now.

report back with this facts.