Strange issue (service battery)

Mi Problema

After 4 year of intensive use my mbp unibody mid 2009 starts to show a problem in the battery (service battery) and its charge was just 0:30'.

So I bought a new battery here on iFixit. Initially it was perfect (the first day the charge was 5hs!) but after ONLY 6 full recharge I have THE SAME problem (now the battery has 1:30 of autonomy).

I've tried the new battery on a friend's mbp and he has the same issue. I've tried everything but I still have not a working mb :(

Mi Solución

Following the good guide of iFixit! Just 5 min!

Mi Consejo

There are lots of taxex shipping in Italy. I've payed 40€ more...