Ubuntu – How to check the battery temperature of laptop? How to know the normal temperature of it

You can open the application "Power Statistics" to monitor the charge and discharge trends for your battery.

If you open the BIOS and go to the Battery page it should tell you if the status is far outside of "normal" for your battery according to Dell (usually if the current maximum charge is <70% of the design charge).

Google Chrome is a notorious battery hog due to the number of background threads it runs for plugins/GPU processes/etc. Try running Firefox or using an extension like "The Great Suspender" to sleep tabs you haven't looked at in XX minutes and you may see much better battery life. Extensions like NoScript and AdBlock that prevent Flash ads from playing can also help. I've found that sites like WebUpd8 and Wikia can really kill the battery quickly due to the number of ads they use to sustain the site.

There are utilities like TLP that can really help with monitoring and controlling your power usage. A helpful article on getting started can be found here.

There is also a GUI for TLP available if you check out this answer