Odd electrical behavior - battery?

[LeeHodges]

Hi

I've seen similar postings but thought I'd ask before I went off on a tangent. So, I went to open my Tamora's door the other day and the click was a bit quiet and the door wouldn't release. Shortly after, I heard an odd vibrating noise that I traced to the door window, which was juddering rapidly. At some stage this then moved to the nearside door. I checked the acumate, which was plugged in, and the battery indicator was red. Turning on the ignition made the lights around the window buttons 'flutter' and there was a 'power error 249' (I think it was) on the dashboard. I decided to plug the charger directly onto the terminals, which interestingly turned the charger's lights to all-good green. The juddering of the doors became more agitated when the charger was plugged in. Is this behavior consistent with a dead battery (I would take it to the battery folk down the road but the last time I went in I had the impression that I was sold something I didn't need...)

Thanks in advance