I have an old early-2008 Macbook which I'm using only occasionally (my main machine is now a mid-2012 Macbook Pro).
The old Macbook's battery, since it was a 3rd replacement, still has about 90% capacity. However, I've left it in the Macbook and haven't recharged it for several months now.
Now, when I plug it in, it doesn't charge ("Replace Now"), the light on the charger connector turns green after 2 seconds of orange; and the laptop is powered from the grid. The Battery Health Monitor app (which tells me that the capacity is still ample) tells me that the voltage of the battery is approximately 7.01 V.
Is the battery dead forever? Or is there a way to revive it?