?? VE SV6 error codes 7A8 engine/7A8

[4Runner conversion]

Bought car yesterday 06 sv6 180 klms, all good. This morning it won't start. Symptoms match flat battery @ 1volt. Error code 7a8/7ae display "contact dealer". Have i ruined it by leaving the key in the ignition? Can the battery lose 12 volts overnight? What could I have done? Any advice, it won't jumpstart.

 

[VTS5]

Tighten batt. terminals
Connect cable to terminals in the engine bay,wait few minutes (preferably with running car)
Turn key ,
Nothing?
Replace batt.

 

[krusing]

Leaving the key in the ignition in some models, leaves various accessories awake,
When you remove the key, and/or open the drivers door, everything goes to sleep, apart from your interior light, but the goes out after the set time,
Base on the above, it all depends upon how the car it set/programmed.
Rule of thumb, ALWAYS remove the ignition key.