Hi

I am new to the forum and have had my 2006 Audi A4 Avant 3.0tdi for around 6 months with no issues.
I have been preparing the vehicle for getting a towbar fitted so bumper and crash bar removal.
While doing this I disconnected the parking sensors (currently in fault) and the Bose speaker unit in the boot.
Moved the car forwards for more room all OK.
Carried on working and went to restart car and the battery had gone nearly flat my own fault.
Now the issue I tried to use jump leads to my wife's countryman and start of but car just turns over and doesn't start.
I can hear the low pressure fuel pump after trying to start seems OK.
Checked relays the are OK.
Battery isn't currently holding a good charge when engine is started it drops to around 9 volts with no jump leads.
Using jump leads I still saw a drop to around 10volts
The car feels like it is being starved of fuel but I have not changed anything or messed with any connections yet.
No codes come up in VCDS

Could this problem of starting all be to do with the battery getting low earlier or do I possibly have another issue? (Battery on trickle charge at moment)

Sorry for the long winded question but have tried searching without any answers.

Thanks, Ross