525i battery dead, won't start

[sauronsdad]

My 525i is in my driveway with a dead battery. I tried to jumpstart it, but did not have succeed. I called in AAA. They jumpstarted the car - but we had to use the AAA guy's van plus an external battery as the power source. We did get it running. After running it for one and a half hours (on the driveway), I turned the car off. Now, I can't get it to start. All the other electronics in the car are working including the windows, radio, and lights. What is going on? :dunno
(I am depressing the brake pedal when I try to start.)

Updated to add the following: It is 2001 525i. Thanks for the info, MIKYZZ4 and Stuck.

[MIKYZZ4]

You need a new battery !! 2. Pray you don't need a new alternator.

[Stück]

Idling will not charge the battery, nor is an alternator designed to charge a battery from a fully depleted state. This can actually damage the alternator.

Base electronics draw very little current on the battery, the starter motor on the other hand can draw 200amps or more...

Install a new battery, and if it applies to your car (you failed to state a year) have the battery registered so the car doesn't under/over charge it.

[MarcoZandrini]

When a battery is fully discharged there's a chemical process that permanently damaged the lead plates. As written above, buy a new battery.