Is it time to change the battery?

I have had my laptop for nearly 2 years now and my battery is starting to act strange.

First, it will never charge to 100% when plugged in but when I remove it, it will say it is 100 for a few minutes before going back to the actual %.

Second, the status indicator on my laptop which is an asus n56vz is always red when plugged in. Is this something I need to worry about.

Thrid, I don't know if this is to do with the battery or a collection of dust, but my cpu seems to get hot when watching youtube videos in 1080p. This happens no matter the browser I use.

If it is time to change the battery, can you let me know the cheapest place to get it from. I am in the UK so if it is possible to get a cheap deal in a store that would be good, but don't mind using sites like amazon.
 

sora

Honorable
Oct 30, 2013
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11,010

It sounds like it is definitely time to replace the battery although the CPU fan might have gone out as well.
 
Are you sure my laptop has a cpu fan? I thought it has one fan for both the cpu and gpu.