Savage 25 Brushless

[mbistric]

Hi . I am Marin and Im from Croatia , have savage 25 that I converted in brushless . I put motor mount form kershaw and bought EZrun 80A combo for 140$ with 2300Kv motor . I also bought on ebay cheapest 4S lipo battery with 15 C . Savage was going with this battery almost 10 days , then te battery dies . Nov I need new on . I ask You all witch good battery to buy on ebay that would last , and is it better to buy 2 packs of 2S and connect them serial on one 4S battery . I looked at this one : http://cgi.ebay.com/DLG-RC-Battery-3...item3ca64cc6ec

What can You suggest me .
Pictures of a car I will put later tonight .
Thank You all and best regards