Does Engine Running Idle Still Charge The Car Battery?

A car engine is started using a battery and the battery is recharged by the alternator whilst driving. The question though is “does the car keep the battery charged when the engine is idle?”. Although I am 38 years old already, I am fairly new to Cars but I recently put this to the test. Just to let you know why, In my first or second year of driving I was parked outside a supermarket. My wife was shopping and I thought it would be a good idea to stream Netflix to my phone during the wait. I connected my phone to the in car charger but did not fire up the engine. I know women like to shop a lot but it must have only been a 45 minute to one hour wait. When my wife got out and we were ready to go home, I tried to start the engine. Lifeless, called the breakdown service out and it was nothing but a flat battery. That’s when I realized that despite car batteries being extremely large, they don’t last long without the alternator charging them. Another time we had a semi flat battery, I researched extensively to see the best procedure for getting the battery to full strength. The common answer was to drive the car at high revs on a main road.It wasn’t until I recently went camping with my son that I wondered if the battery would go flat if I used the in car electric socket but just leaving the engine in idle (no high revs etc…). I dipped my toe in the water and used it for brief periods of times, worked great but I was still not convinced.

Does the Engine Recharge The Car Battery When Running Idle

Then during another camping trip in the summer I really tried my luck. This was due to missing out on a planned electric pitch. I was forced to charge a usb recharger otherwise we would have to sacrifice use of our phones, tablets etc… I started out with maybe 30 minute trials, all fine. Then 1 hour or more, no problems. All the way up to a 2 or 3 hour stint. Guess what? Battery remained fully charged and functional!!! My only concern now is if the heat from the engine running in idle may have toasted the oil as it looks a little too brown for oil that was only changed a couple of months ago.