I bought a new car recently. Along with the typical 12 volt DC outlet there is also a 115 volt AC plug. I’m assuming there is an inverter somewhere under the hood.
So, when I charge my phone/ipod/etc which should I use? More specifically, would either be faster? Would either be kinder to the car’s battery?
Thanks!
Right off the top of my head I would say that the 12 volt outlet would use less electricity. All inverters (or electrical devices of any kind, for that matter) waste a certain amount of current while operating. Your inverter, if it’s typical, probably has an efficiency of from 50% to 90%, depending on the current draw. The 12 volt outlet would not have this disadvantage.
[Retracted as I see the OP is referring to an internal outlet]
Sorry, it is an outlet.
OK, I can see how the DC would be more efficient. What about speed of charging though? If my cellphone battery is about gone and I’m driving 15 minutes to a friends house, which would give the most charge (disregard that I could just plug it in at my destination).
I would assume that they would be the same because the power output at the end of the charger that goes nto your phone would be the same (probably five volts, 300maH).
BUT
I used to work at T-Mobile a LONG time ago. Back then car chargers would charge the phone faster but the charge wouldn’t last as long in my opinion. An other way of saying it would be that the bars on the battery life gauge would go up faster on the car charger but you would burn through them faster at the same time.
either supplies far more than the charger can use.
Voltage alone is not enough to determine charging speed - as any adapter will reduce the voltage to that of the device and probably affect the amps as well. In theory, your device’s adapters(Car DC vs AC) will both have identical settings for output Volts/mAmps and therefore work identically.
Inverters typically run at around 80% efficiency, so 20% of the wattage you put into them comes out as heat. Your phone charger will then have to convert that AC back to DC in order to charge the phone’s battery, a process which is also less than 100% efficient.
Cool. Guess I’ll use the AC strictly for shaving. 
Right, but in the case of charging the cell phone, this shouldn’t make a difference because what is on the back end of the process isn’t changing what is coming out of the business end of the phone charger, right?
You’ll likely have a wall-wart style charger that uses AC and a separate cable for hooking up and charging via 12VDC, or 5 if thru USB. They all end up putting out the same DC voltage and current, but going through the AC intermediate is a less efficient way of producing the corrrect DC power.
