Good battery for an E53

[Tymatk]

Folks

I have a feeling that my batt is on it's way out. Where is a good place that I can get a battery for the shit box? In Melbourne by the way.

The car was fine until a month or two ago, I accidentally lock the car with the key in the ignition and the damn radio was on as well. The wife have the spare key and she works in the city so by the time she got home, the batt was already flat!

I hook the charger up for a few hours, started and she fires up fine! A few weeks later, I left it home for a day and the batt is flat again! I went online, research and found that I need to take it for a long drive so that the batt can be fully charged.
Apparently even though the car is shut and lock, shit is still running in the back ground hence if the batt is not fully charge, there won't be enough power to crank the shit box.

So, yesterday I left it home again. Today I just bought a used roof rack for it, getting ready to carry my snowboard gear this winter. Trial fitting the rack, was going take it for a test drive to see how bad the wind noise can be, the Shitbox would not start . Hook up the charger again, this time Transfailsafe message came up, I feel like pushing the damn thing down the clip to end it's and mine misery !

Anyway, enough complaining, what batt, spec, brand that I should be looking for?

Thanks

[Tymatk]

Transfailsafe is gone, weird! It must have recognized that the batt is now has sustained a reasonable amount of voltage in there. I'm going to leave it charges until it's full this time.

[Quicksilver]

You may find this strange but I bought mine from the dealer. After a 20% discount the price was competitive with everyone else.