I'll cut the long story short really, went to see my gf and when i left we went and sat in my car for a bit before i drove home.
Sat there for about half an hour (in a mk4 hatch) at which time i had the heated rear window on, fan on setting one and cd player on, on volume level 5 but i do have a sub and amp to, but the volume wasnt on loud. Just when i was going to leave the cd player flickers off and stops playing. Then the button for the rear heated window light wasnt on anymore. Turned the cd player on again and it came to life then died again and the light on it dimly flashed a bit at which time i was bricking it thinking the wiring was messed up.
Went to start the engine and it barely turns over, with every turn on the motor the interior light went off and on (thats how little power was there).
Tried starting it again and the engine starts to turn over a little more easily, and in about 10 seconds of trying it coughs to life. So luckily i managed to get home.
Dragged this story out a bit i guess but ive got a couple of questions now:
1. On my Corsa B which had a knackerd battery on it and the same sound system as on my Astra, how come i could play music with the engine off much longer and the car would start fine, yet on my Astra it killed the battery on a quiet volume in half an hour? It is the original battery and its an 04 plate.
2. Does the ECU somehow gather all power and send it to the starter motor because when i tried to start it it barely turned over, but when i kept trying it seems to 'loosen up' and started. It was also strange how the rear heated window stopped working as did the CD player.
Everything is working now though obviously, i drove home with no electrics other than headlights to try and get the alternator to restore some power.