Hi Robwizard, I was reading the other post, how many days have had off your car?
I Have had a similar situation with my 480, the battery died without using the car.
I replaced the battery and i have made a small test of consumption,
to see if there are consumption on battery while the car is off.
It's easy, with the car off, remove negative from the battery (You can take either but it's more safe to take the negative)
and do a bypass with a tester (consumption adjust scale to Amps).
Later you can prove to remove the fuses one by one and discover your car
In my case I discover that the radio with the cover fitted has a consumption of 0'26A!
You can calculate how many days hold out with your battery amperage in hour.
(45Axh/0'26A= 173'07hours/24h that have one day= 7'2 days of battery)
(I think it's correct calc x'D)
If it's an fuel car, you don't need a bigger battery or more capacity.
I think you have to do the test of consumption and replace the battery.