I have a Escort h reg 1.6i cabriolet, and when left off for a while i can go to it and start it fine, but when i stop somwhere like the chemist or pet shop, i cant start it as if the battery is dead, i bought a brand new battery but i still have the same problem, im a bit dumb so excuse me, so is there any simple explanation to my problem thanks, need help quick as my dog needs food