New battery draining fast, SMC doesn't help

Hi,

I just got a second hand MacBook. It is quite old (2010) but everything is running smooth and fast. The only problem is the battery. I tested it with coconutBattery - it is a brand new battery running on 115%; however, dies in only 30 mins of browsing the net.

Is it worth it to even get a new battery for old macbook? Is it better to get an original one from apple? Also could it be the hardware problem?

Thank you