I have a Compaq Presario CQ61 for 4 years. Purchased all in 3 different suppliers two 4400 mAh batteries that were no longer recognized after 1 month of use and a 8800 mAh (lifetime 2 years). You have to buy the 8800 mAh first because it elevates the pc so it is overheated less and then it lasts longer. I advise against commercial sites, especially the site "Battery laptop", apart from Amazon, which has taken in stride the defective battery.
I have found nothing better Amazon, for all its offer.
Latest news. Anker contacted me after putting this comment. They were very courteous and offered me to change the battery immediately. That of 8800 mah is guaranteed 18 months. To see more ...