Hello!. Well, I bought a TT-01 chassis with a 1500 battery about 2 years ago. The car would run for about 4-5minutes also. What you have bear in mind is a few factors.
1) The charger wont get the max charge out of your batteries
2) The silver can motors included are very inneficient
3) Its not a very high capacity battery in the first place
4) It runs on bushings which equals more friction/resistance.
5) It most likely came with an MSC which are inefficient buggers.
I would say this is about normal. Id advise you to buy a Cheap ESC, these can be bought for around 25quid and make a large difference, expect maybe 30seconds more runtime and smoother throttle control. Then, think of investing in a set of bearings for your car, these should be around 5quid from abroad. Finally, perhaps buy a higher capacity battery to get longer runtimes, maybe a 3000nimh which can be bought for around 20quid. If not, you could just buy the battery alone and get about another 2 minutes runtime and a slghtly faster car. Thanks, ask any more questions if needed and stick around.