Several of my Xbox 360 Plug & Charge Kits aren't holding charges anymore—they will turn on and connect if linked with the wire/cord/cable, but will turn off once the cord is unplugged. This happened suddenly—it's not like the battery capacity slowly drained over time.
I had noticed in the past that certain batteries work with the gray cable (from the original kits) and not the black (later version), or vice versa. E.g., a black battery will connect and charge with a black cable, the indicator light turning red after a short delay, and then to green after a few minutes. That battery will appear to stay on when unplugged and the dashboard will show the battery as full, but it'll turn off abruptly after a half hour or so. If I use a gray cable to charge the same battery, the controller turns off immediately after unplugging. I'd like to be able to use cables between batteries interchangeably, if possible.
I'm not seeing much useful feedback on other forums, though this issue seems relatively common. What is happening here? Are the original gray and black kits incompatible? Is the battery close to complete depletion and uselessness? What are the indicators of total depletion? I saw some videos on YouTube about artificially draining the battery—would that help? Is there some catch-all solution to this issue?