I have a discharge warning light on in my car. The car will start and run for a while (on a charged battery) but it soon powers down (dash and cabin lights dim to almost zero) and the car shuts off.

it has 2 or more problems
battery bad or allowed to discharge or alternator dead
fuses blown.
and very low fuel pressure. (no engine told)
it at least runs, and when it does the dash lamp cluster CHARGE/BATTERy warning lamp must be out, IS IT?

When you start your car the battery starts it. When the car is running the alternator makes the voltage to run your car and it recharges your battery. If alternator is not putting out enough voltage then your battery has to run your car and it will get to a point the car shuts down due to lack of voltage. The cars computer now day will starting shutting down thing which use voltage if the car does not need it to run when the voltage get to low. My 2006 cobalt, I lost the radio, A/C and even the power steering electric assist motor when voltage got low. Charge your battery, crank your car turn on headlights and check voltage at the battery it should be over 14 volts even up to over 15 on some cars. If not you may have alternator problem or wiring problems.
links with additional info below
https://www.youtube.com/watch?v=30ab7ueJ2H8
https://www.youtube.com/watch?v=AzjcZuk7sNg
https://www.youtube.com/watch?v=pwiO4nvSbeY

It sounds like if this is a car with the brake interlock, meaning the car will not shift from park unless the brake is pressed, there is a malfunction there, some are electronic and it may not be getting power to it especially if there are other warning lights on the dash. It would help if you could give more details, like which lights are on. Most cars with a mechanical interlock will have a cable you can adjust either at the brake cable or at the shifter.

Maybe your battery is discharged - did you check that out? Alternator warnings are there to let you know that the charging circuit is not working. And when that happens batteries discharge, and car will not start!

If you know for a fact the alternator is working, the problem could be an open circuit between the alternator and battery.

Check all your battery connections. Maybe not a good connection since your key doesn't turn on warning lights and gauges. See if your headlights work to verify a good battery connection.
Any chance you blew fuses? Like a maxi fuse for the ignition switch? Or for older vehicles that used a fusible link to connect battery power with the ignition switch. Keep diagnosing until you get power to the ignition switch (warning lights and gauges working with key ON).
Any chance your battery is totally discharged? Was the alternator working good when tested? If alternator quits working, engine and all electricals will run off the battery for a time until it is totally depleted, then will stall and won't have enough juice to even turn any lights on. Check battery voltage with a multi meter or voltmeter. A good, fully charged battery will show 12.6 volts. If under 12 volts, it may or may not have enough juice to start, but lights will still work some, though maybe very dim. .

The light that looks like a car with an exclamation mark in the middle of it is the HYBRID WARNING light (see diagram below) You must scn the onboard computer network to determine why this light is coming on. You also need to scan your computer system to find out why the engine keeps dying. If the hybrid batteries are discharged, they must be properly recharged to prevent serious damage.

CAUTION: Read ALL service and warning lables in the engine compartment before attempting ANY type of service on a hybrid vehicle. The wiring harnesses that have ORANGE connectors are HIGH VOLTAGE connectors and can cause serious injury or death.

DO NOT touch any wiring harness or component that has a HIGH VOLTAGE warning label on it.

My recommendation is to tow the vehicle to a qualified hybrid repair center (preferably the dealer) and get it properly diagnosed and repaired. The high-tech, high voltage systems in this vehicle is nothing for anyone but a trained, certified technician to be messing with.

It sounds like your alternator is bad. East way to confirm, take it to local auto parts store (IE: Autozone, Advance, etc) and have them do a FREE charging system test. Couple of thoughts; you have two new batteries and your poor alternator has to work twice as hard. After you put new batteries in, you've been running on straight battery power. Alternator normally runs all your electronics and recharges battery(s) but if Alt has gone "south" then you're on straight battery power.

Your battery is discharged. Jump start the thing and leave it running for a bit (outside, of course) to re-charge the battery. Check the interior lights, etc. because someone probably left an overhead light or something like that on.

The battery has discharged enough such that it will not start the car, but not enough such that it will not light up the little ***** light bulbs on the dash, etc.

check for loose wire behind the alternator when the light are fading our running on the battery only the alternator ir not charging get that check as soon as you can the frestar gonna stall soon thanks pierre