I bought in Greece a 1450mAh Li-ion 3.7 V 5,37Wh for 15€
with the name 'Reverse' (in greece the reseller names it NetOne)
made in PRC

I used the first time with the charge it had and when the indication
get red i charged from the usb cable for 10 hours.

But the first two times the duration is less than 24h in not frequent use (1-2 calls , 1 hours photo/video)

It says it need 3 recharge cycles to display max perfomance..
let see.. i 'm douptfull ..

In the past after the nokia BL-5J that came with my second-hand n900 which lasted less than day i bought from ebay a PolarCell Akku Li-Ion following forum advice that indeed proved very good and lasted 2 years!! (the top cap came off after many falls and maybe shortcircuited? i'm not sure but my multimeter show it's dead).

I bought also a 1 x PolarCell Akku Li-Ion from cellphone.de but that never came :-/ and they want me to sing taking full responsibility if their inquiry shows that the mail service sent the item. I kindy reclined and having lost 15 euros i took the local alternative cause having 2 months with no n900 was too long for me)