Do you have it plugged in when you are driving? I'm wondering if this "It is the exact same sound as when I plug it to charge" means the voltage to the iPhone is varying enough that it thinks it is being plugged and unplugged.
Firstly where in the charge cycle is it (has it reached 100%) basically the "chirping" sound is it NOT loosing charge but loosing the charge connection, new iphone is very susceptable to voltage change from the charger and some cheap chargers do not regulate the voltage correcly - to see just look at the charge symbol if it is charging then it will have a lightening symbol if fully charged a plug symbol if not charging then a battery only symbol
this is a know problem ... i have seen a lot of people post about it (not here) and experienced it myself... dnt worry.. the noise you are hearing is a verry high piched noise that only teens should hear (aka me) so your lucky to hear that high xP
I think it may have to do with the charge state. does the iPhone turn off the charge connection when it is full and open open it back up when it drops a little low?
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Iphone makes chriping sound while driving
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