Vexing Problem - The Ghost in the Machine?

I have an '02 Mitsubishi Diamante with 201,000 miles on it. So far, I’ve only spent $2 in non-wearing parts (brake pads, etc) and it runs like a dream. Actually, it ran like a dream until yesterday. Now I can’t figure out what the problem is; here’s the deal:

On my way to the grocery store yesterday morning the radio shut down (in the normal sequence) as if the key had been removed. I parked at the store and when I got back in the car, it started normally and the radio worked again. On my way from the store, the radio cut out again and then the brake light flashed. Eventually, the dash lights started to go in and out, the brakes started to get harder to push, power steering became intermittent, and then the car died. It would not restart, not cranking when I turned the key (not even clicking).

I got towed home and started taking it apart. All the fuses are good. I get good continuity between the battery and ground. The battery read at 10.8 volts. When I put the key in and turned it to run, the dash lights turned on and the engine cranked weakly when I turned it to start. Then, when I tried again, I got flickering dash lights and no crank. The I got nothing.

I hooked up the car to another battery and could only crank it when I connected it terminal to terminal rather than positive terminals together and negative to chassis. I got strong dash lights and good crank, but even after many attempts I could not get it to start.

Based on the weird combination of problems, I’m searching for an explanation that would make sense. What should I be checking? I’m out of ideas and can’t really afford a new car right now.

If the battery reads 10.8 volts when you read the voltage DIRECTLY AT THE BATTERY TERMINALS it has failed or is deeply discharged. I’m betting you need a battery.

Take it out of the car and have it tested.