New battery and new alternator in my 08 Honda civic 1.8L
 

I'm wondering why my new battery and alternator are draining my power or what it causing my battery to die. Just bought the battery 2 days ago along with brand new alternator. It died on me driving home from work due to no power. Can anyone help me or suggest anything yall can. I just bought this car from my brother it's well kept and I dont know anything about hondas at all. Thanks