2004 330 xi - no power after battery disconnect

[CapeCams]

Hi,
Before I explain my problem I should note that I know I have needed a new battery and occasionally have to throw my charger on it to get it to start if it has been sitting for several days but I always get full dash and then a click. Last night I did leave the key turned in the ignition.

Today I replaced my oil filter housing which required removal of the alternator. I disconnected the cable from battery before I removed the alternator. Put everything back together and now have no power. All I get when I turn key is the airbag light. Keyfob does not unlock car. No lights, windows, etc. I put the charger on it and after 10 minutes it said it was fully charged.

Is my battery stoned dead or did I do something wrong with the disconnect?

Thank you.
Cams

[charter21p5]

Check voltage if the battery

[CapeCams]

Voltage was low, New battery was the solution.
Thank you