Question about a battery issue on 08 LTZ

[SmoknLS1]

So, just wanted to check with forum members before I go get the battery tested but here is my issue: Tahoe starts up fine every morning but twice now I have run the battery down in a parking lot by using the liftgate a few times between startups. This seemed somewhat odd unless the liftgate is just using up too much cranking amps on a failing battery?

Also, the two separate times of running the battery down are about 4 months apart. Other than that, the battery never hesitates on startup.

Thoughts?

 

[Tex99Tahoe]

My experience with these newer high CCA batteries is that once they've run down, they may appear to charge back up, but the capacity is gone. Has something to do with the 'sponge' lead design, greater surface area compared to traditional deep-cycle flat plate design. More surface area increases crank amps, but during recharge the lead replates elsewhere, reducing this effect...