I have a MacBook and I did not take care of the battery properly. It started to shut down unexpectedly at around 20% and then even at 30%. I got a new battery and it seems to work fine; it lets me get down to 6%. The only problem is that even with the new battery, a warning does not pop up telling me that it is time to plug in my computer. I was waiting for it to come up when my computer was at 6%, and instead it just died. I don't know if I need to change some kind of setting or what. Any ideas on how to fix this?