I have a 2014 rMBP 13" which I used extensively on a daily basis. I purchased AC for the sole reason of protection against battery depletion over the coming years. It's hard for me to tell whether my battery has lost capacity, but I'm sure it has against the original figures when I first got the machine. My question is, when will AC be willing to replace the battery due to loss of capacity? Is there a percentage? How can I test it?