Hello everyone,

I drive a Ford Fiesta titanium 2015, i've charged my phone using the usb car port, while the engine not started, then when i cambe back the next day, the ca wouldn't start, and all the system just got nuts. I thought it's the battery, so i used a jump start, and it worked, but when i got to the shop they told my battery is fine, and for 2 days know the car is fine, so my question is do have any idea why i had this episode? Is it related to the fact that i used my phone in the usb car port?

Yes, your phone battery took the charge out of the car battery.

The car battery only gets recharged while the engine is running.

11 hours ago, TomsFocus said:

Yes, your phone battery took the charge out of the car battery.

Now if the OP had a decent mobile, he could have used the phone to jump start his car 🤣

A shoe 'phone as we used to call them.  Incredibly rugged, would still work after a six foot drop onto a road !

For the youngsters, six foot means nearly two metres !

On 10/27/2024 at 10:33 AM, TomsFocus said:

Yes, your phone battery took the charge out of the car battery.

Would it ?  'Phone battery might be a couple of Ah@5V, car battery 50Ah@12V, so surely would "never" discharge a reasonably charged car battery ?

34 minutes ago, Paulkp said:

Would it ?  'Phone battery might be a couple of Ah@5V, car battery 50Ah@12V, so surely would "never" discharge a reasonably charged car battery ?

I won't pretend to know the exact science behind it, but car batteries don't seem to drain in a 'linear' way from full to empty.  It really doesn't take much to push them below the limit of powering the starter motor.  I suspect the battery in this case was probably old and reduced capacity as well, the garage probably just checked the voltage rather than capacity.  I suspect the BCM is also kept awake while power is taken through the UBS ports as well.

On 10/28/2024 at 1:47 PM, TomsFocus said:

I won't pretend to know the exact science behind it, but car batteries don't seem to drain in a 'linear' way from full to empty.  It really doesn't take much to push them below the limit of powering the starter motor.  I suspect the battery in this case was probably old and reduced capacity as well, the garage probably just checked the voltage rather than capacity.  I suspect the BCM is also kept awake while power is taken through the UBS ports as well.

I hear you, but if the battery was drained out by the phone how is it still working till today, that's what i don't understand.

49 minutes ago, Aladin said:

I hear you, but if the battery was drained out by the phone how is it still working till today, that's what i don't understand.

It gets refilled by the alternator every time you run the engine.