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Draining the car battery

So, will charging the cell phone in a car drain the battery if the car is not running? My husband and my brother-in-law both agree that my sister and I are totally off on this one. Please tell us because right now we are arguing about this too often.

Letsseehere… the battery in my cell phone is 3.4w. A 500 CCA car battery stores about 6000 watts. So you could completely recharge your cell phone at least 1000 times before you actually drain the battery to a point that the car wouldn’t start.

The amount of energy small electronics is pretty insignificant compared to the amount of energy needed to turn an engine over. I’ve accidentally left my satellite radio on for weeks and the car still started.

No, charging a cell phone in a car with the engine off will not drain the battery noticeably faster than not charging a cell phone in a car. You can leave it connected and charging for over a week with no problems.

I wouldn’t worry about it either. Carry an aux jumper battery in the trunk with a DC jack and use it regularly out of the car too if necessary, esp camping…and don’t worry about it.

In some cars you have to have the key in the ignition and set to ACC (accessory) to get power to the 12V DC outlets. This means more stuff is on in the vehicle while the phone is charging and the key is in the car, a security hazard. My cars are like this so charging the phone when off is a rare, emergency, occurance. However it doesn’t run down the battery.

If your DC power outlets are on all the time in the Explorer then no problem.

I would bet that the electric wind spring driven clocks we had back in the old days from the 1930’s through the 1960’s consumed more power than the power required to charge a cell phone battery. These clocks would rewind about every 2 minutes. We certainly didn’t leave the engines running so that the car battery would stay charged to keep the clock wound up. I often while traveling let the car battery recharge my cell phone battery overnight. I’ve never had a problem.

I had a ac/dc converter in my cigarette lighter adapter that caused my battery to drain. I couldn’t figure out the problem, and ended up being referred by my car mechanic to an electric specialist. Cost me a couple hundred bucks to find out the converter will drain my battery. Something to know - the specialist hadn’t seen that one before. gl.

This is interesting. I would not think that the converter (dc to ac) would draw power unless you had something plugged into the converter. In the case of the cell phone, the car battery is already supplying direct current and the cell phone battery needs to receive direct current to be recharged.

Cigarette lighter charger, assuming a cigarette lighter.

the car battery is already supplying direct current and the cell phone battery needs to receive direct current to be recharged.

But unless that cell phone is 12 volts (maybe less), it will need to adjust the voltage and that is usually done by converting to AC and then back to DC.

No, car phone chargers use a DC to DC converter, mainly because that’s cheaper and smaller. It has the added benefit of being much more efficient than a DC to AC to DC scheme would be. Also, they cut down to a few milliamps or even micro-amps once the phone battery is full.

Typical cell phone batteries are 3.6 volts. Usually, the cell phone needs a 4.5V to 5V source to charge the battery from.

The simple and cheap way to do this (from a 12V car battery) is a linear regulator. It wastes over half the power used as heat, but the power used is so low that it doesn’t matter too much. It also consumes almost no power once the battery is charged.
The better way to do it is with a switching regulator. That’s only slightly more expensive, and it wastes less than twenty percent of the power as heat. These also draw almost no power once the phone is charged.

The only phone charging scheme that I know of that would use an AC converter would be where someone would use a 12V to 120VAC inverter and then plug a 120V cell phone charger into that. I am assuming that this is not at all what the OP was talking about.

If you can point to an actual cell phone car charger that uses an AC converter, please provide a link to it.

Some of those little chargers are so inefficient, they pull more power than you might expect…But a car battery could recharge a dozen of them without any trouble…