which laptop's battery is the best?

Battery is some thing else and laptop is some thing else. The battery which works for a long period is considered as a good battery. If battery takes time in charging and they become weak very soon then those batteries could not be considered good. Is there is no defect in a laptop then the battery work properly, if the laptop is defective then the battery becomes un-charge soon. Good battery causes the better performance of laptop, while bad battery do the bad with laptop.

Last the longest? That would definitely be Sony... That's also because Sony manufactures battery and also OEM it to other laptop PC manufacturers...

I have seen a few laptops with 8 hours of battery life. Most of the ones these days are 2-4 hours of battery life. I just heard a few days ago that scientist found a new breakthrough on computer lithium batteries. They found a way for them to last up to 40 hours! No idea when this will come out, probably not for another few years though. That would be really good if they would last up to 40 hours. No need to plug in anymore, and you will be able to run bright screen.

last longgest? i think japanese laptop battery is the longgest,like sony,nec and so on,sony vaio tz serials can up to 11.5 h,and nec verspro ultralife can up to 14.5h.