Need help with battery life

Hi guys,

I have decided to get a 15.6 inch laptop for general use. I prefer a model that is light-weight and has good battery backup.
I saw some models in Flipkart. But I feel that the battery backup value given in Flipkart is wrong. From where can I get the exact battery life?

Here are some products I'm interested in:
HP Envy 6-1002TX Sleekbook
HP Pavilion M6-1005tx
HP Pavilion M6-1002tx

These models have less weight. I have seen in HP site that Pavilion M6 has 8 hours of battery backup. But Flipkart tells that it is just 3 hours! Who is right?
I know that the battery backup for Envy 4 series for 14-inch model is 8 hours. So it should be somewhere in the same range for Envy 6. Again Flipkart tells otherwise!

Please let me know the proper battery backup for the above product guys. Also let me know from where I can get the battery backup value for all laptops.

flipkart is just an online selling site, not some tech review or news site. All specs are not perfect in laptops specially about battery life. They generally mention their laptops with wrong battery life. (mostly with 3 hours of battery in every brand).
AFAIK Envy 6 has battery upto 6 hours. And I'm not sure about M6-1005tx & 1002tx. They are proper laptops with 6 cell battery not low power efficient ultrbooks. So, I guess battery would be normal around 4-5 hours.

I have seen in HP site that Pavilion M6 has 8 hours of battery backup. But Flipkart tells that it is just 3 hours! Who is right?

Lot of information availble on FlipKart are incorrect alongwith the biased reviews.
Ultrabooks have a backup of more than 5 hours as such. And normal laptops have around 3-4 hour on average usage.

i think ultra books have 7 hours of battery backup because of underclocked 3rd gen processor with no dedicated GPU.

RON28 said:
i think ultra books have 7 hours of battery backup because of underclocked 3rd gen processor with no dedicated GPU.

Some ultrabooks have dedicated GPUs but can be switchable with low performing Intel GPU.