Battery 79% life after 72 recharge cycles and Amperage -1356

Question

Hi to all, this is my story, I've bought a macbook pro 15'' on November 2007 and in about 4 months battery was at 50% of life after 92 recharge cycles, after one year from purchase, apple store has changed battery, megasafe and the connector on the macbook, now the situation isn't changed and I have a battery, like in object, with 79% of life after 72 recharge cycles and the Amperage in the information window is (-1356) very strange!!! Why there's a negative amperage? and why my battery works so bad? I always charge the battery when is completely discharged and when i do this the macbook is off, sometimes I use macbook with megasafe connected but in this situation I remove the battery. Can i have a new battery from apple in free substitution?

Answer 1

Hi alby_mo and welcome to the forums.
The amperage figure you mention will ALWAYS be negative when running from the battery and be positive when the battery is actually charging.
Your battery life is not uncommon, (many people only get about 18 months life out of these batteries, I'm afraid) but you are going about the charging process all wrong!
You should avoid completely discharging Lithium batteries as much as possible, and use them regularly and lightly if possible. Discharging them completely all the time reduces their lives substantially. THis used to be a good idea in the past with NiCad batteries that would develop a "memory" problem otherwise, but it is not so with Lithium batteries.
The only time that you really need to completely discharge your MacBook Pro battery is when you "calibrate" it, which you should do every month or two. See http://support.apple.com/kb/HT1490 for instructions.
See http://discussions.apple.com/thread.jspa?threadID=1764220 for a good FAQ with information about how to look after your battery, together with Apple's own comments at http://www.apple.com/batteries/notebooks.ht
You should stop running the computer without a battery installed, too, for the reasons set out at http://support.apple.com/kb/HT2332. It has little effect on the battery because charging is disabled once the battery reaches 100% and doesn't start again until it has dropped to the mid 90's. Better , instead, to get into the habit of running the computer on battery for an hour or so each day, and just leaving it on the charger the rest of the time, whether you are using it or not.
The "health" of your battery seems to reduce when the charge gets low because dying Lithium batteries build up increasing internal resistance, which becomes more apparent as the voltage drops.
You can ask Apple service in Italy (or an AASP) about a free replacement, but I wouldn't get your hopes up. Many people with 2007 MBps are already on their second and third batteries, and Apple generally will only replace them during the warranty period. Some people seem to get lucky, though, and you can't lose anything by asking!
Cheers
Rod