Flat ??? Battery

[Robsey]

The obvious answer is...

A - look for product reviews on the tinterweb.

B - Read the labelling. You are interested in the storage capacity and the cranking capacity.
You are looking for as high a figure as you can find.
You also want a battery with a good warranty period, as they can range anywhere between 2 and 5 years.

You cannot expect any of them to last 9 or 10 years like original factory fit batteries do.
I don't know why, but genuine batteries always seem to last longer in my experience.