[MoFoHo]

Hi all wise ones.
I've just spent the weekend fitting (or at least struggling to fit), a dashcam.
Running the hard wiring kit was a nightmare, getting the wire from the cabin into the trunk/boot especially, but I eventually managed to pass the wire through underneath the back seat, in a place where the first aid kit fits. After a LOT of faffing about and testing both days this weekend, I finally managed to get battery and accessory power to the device. A lot of the time, I admittedly didn't always have the engine running, but only 5/10 mins here and there, testing stuff.

But yesterday (Saturday) shouldn't count because every night, the big 6ix is put in my garage and connected to a Cetek battery tender.

So today, after finally getting stuff sorted, I noticed the car struggling a little to start, so I wisely backed the car back into the garage, and sure enough, on attempting to start it again, the battery was pretty much completely flat. It seemed that just a short while faffing about completely flattened the battery! So, luckily, I was able to put the car on the Cetek MXS-5.0 battery tender. An hour later, and the Cetek was showing a full house of lights (up to light 7 anyway) and the car fired right up. I was expecting the charger to take 24 hrs, at least, to accomplish this task! Yet it was fully charged in just over an hour. I think I read somewhere that this short charge cycle is indicative of a battery at the end of its life, is this true? There were no errors whatsover while the car was struggling to start BTW. Do I need to consider a new battery? The car is 9 years old, a 640d.
Any help please?