I left my car outside my home for a week while on holiday,when i came back and tried to start the car the battery was completly flat. This is the first time it's gone flat, i have left it for up to 2 weeks before and its started ok the only difference this time was the very hot weather . Battery is only a year old nothing was left on like radio, lights ,alarm etc, does a car sitting in hot weather drain a battery so much ?
Without knowing the state of charge before the car was left, any answer can only be a guess. It's highly unlikely that the weather has anything to do with it. Battery might be duff. Maybe it needs topping up. Maybe the cars charging system is not up to scratch. Maybe there's a drain on the battery you haven't noticed, boot light not going off, as an unlikely example. Try switching everything off, and connect a DVM between one of the batt terminals and it's lead. This'll tell you what current is being used when the car is parked. Checking all the above should find the fault, if it has one. Mike.
Some things like the radio and alarm will take a small current whether switched on or not, but the battery should certainly cope for a week unless pretty flat to start with.
The best thing is to check the quiescent current - ie that drawn with the car in it's normal parked state. You'll need a DVM or ammeter that reads up to about 10 amps.
It should only read a few milliamps - say under 30 (0.03 amp) unless there's a fault. If it reads about 5 amps, the first guess is a faulty alternator - disconnect it to prove.
Also check things like boot and under bonnet lights switch off.
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