jerryc41 Loc: Catskill Mts of NY

I've read a couple of articles about the negative aspects of charging a cell phone in your car. I've been charging cell phones in cars for years without problems.

1. The USB port doesn't put out enough current.
2. The 12v outlet puts out too much current.
3. If the car isn't running, you can kill the car's battery. Considering the size of the car's battery vs the cell phone battery's, I wonder.

Any opinions?

tradio Loc: Oxford, Ohio

I have had no problems.
Newer vehicles have chargers that only require you to lay your phone in a certain spot and it charges without any physical connection.

srg

My Toyota Tacoma has 2 key positions while not driving. This summer my cellphone was almost dead, so while doing a quick 2 hour job, I decided to leave phone in the truck to charge. I used the 2nd setting of the key which activates everything. 2 hours later my truck battery was dead, It became an unusually cold night, I was only wearing a T shirt, the customer was not home, I couldn't roll up the window and had only enough battery on the phone to call home. She made a call to AAA and about one freezing hour later a truck pulled up to start my engine.

Dannj

I charge my phone only when the car is running and never leave a key or charger in when the car isn’t running…had a bad experience with emergency flashers.

marshall_b

HI ,I only charge my cell phone while driving

Indi Loc: L. I., NY, Palm Beach Cty when it's cold.

Whenever I drive more than a few miles my iPhone is always connected to my cars entertainment system and therefore, always charging.
No problems so far.

hcmcdole

The cigarette adapter comes in different amp outputs (get the one for your phone's rating for quicker charging). I bought a triple charger years ago for my old truck and two ports were higher amperage and the third one was a slow charge for the older type phones.

Make sure the adapter is pushed all the way in - no telling how many times I lost power on the phone while plugged in and then to find out that the adapter wasn't all the way in! The worst case was using the phone for GPS guidance in a city and lose power without any alerts that I was dangerously low on power. GRRR!

My new SUV has a dedicated charging port that also puts the phone (maps) on the NAV/Radio screen - very cool! I lose voice control for the Sirius radio though but everything else works - navigate to XYZ, call ABC, etc. I prefer Google maps over the built in NAV system of my SUV anyway.

If a cell phone kills the auto battery then the auto battery was on its last legs to begin with. My wife's Toyota will not charge our phones when the engine or accessories is turned off. Bummer, as I cannot charge my nearly dead phone if we are at a store - found that out after I left my phone in her car for an hour or more.

JBRIII

I don't doubt what happened, but we need an expert here. A battery block can recharge a phone several times and has nowhere near a card battery capacity. I ran converters off car batteries to generate 120 AC which ran several cameras during the 2014 eciplse without any problem. Also, while a lighter socket can delivery many amps, amp draw is based on device need or else all 120V 15A would deliver 1800 watts to any 120 device, destroying most devices. Even if the resistance in the wiring, etc. was high enough to drain a car battery that quickly, it would probably cause a fire. ?????🤔🤔🤔🤔🤔🤔🤔🤔

47greyfox Loc: on the edge of the Colorado front range

Most newer American cars automatically turn off USB ports after 10 minutes or so.

Jim Plogger Loc: East Tennessee

Best practice. Only charge while driving. Never have had a problem.

burkphoto Loc: High Point, NC

Yeah, in my Prius:

The USB port was made for an iPod. It cannot charge an iPhone.

The 12V outlet puts out (nominally) 10.2 to 12.6 volts in Accessory Mode, and about 13.4 to 14.2 volts — normal charging voltage — when the car is in READY mode. It puts out a maximum of 150 Watts. That isn't "too much" or "too little" current. Maximum current would be around 12 to 15 Amps. What matters is the output from the charger you plug into the 12V outlet. Most phones require a MINIMUM of 5 Watts at 5 Volts (25 Watts, because Watts = Volts x Amps...). Newer phones with fast chargers or inductive charging can draw a bit more, but 150 Watts should be plenty for a couple of car chargers.

So most important is the *design and construction* of your car charger. If you bought the sub-$5.00 kind found in convenience stores, gas stations, and novelty shops, it probably isn't voltage-regulated and filtered properly. If you find that your phone gets hot when charging in the car, but stays cool when charging on the OEM charger at home, throw away that cheap car charger and get a good one. Low output voltage causes the phone to pull more current, which heats up the battery. Some of the cheap chargers put out only 3 volts.

In many cars, mine included, the 12V outlets won't stay on unless you keep the car in Accessory mode, which requires keys to be left in the car. Leaving keys in the car is stupid unless your car is in a "no crime zone," such as a locked garage! And unless there is a LOAD on the charger in the 12V outlet (such as a connected phone), there isn't significant current draw to cause a battery to drain over night. In cars with keyless remote entry, you're likely to drain the battery from letting the car sit for two weeks without driving it, if you don't turn off the keyless entry feature.

My twins bought a cheapie charger when they started driving. I had already taken both their iPhones in for new batteries, when I called them into the garage one day, put their car charger on a 2x4 on the floor, and smashed it with a sledge hammer. Then I handed them a new one (10-Watt Belkin, I think it was). I got a puzzled look from them, then explained that their phones were dying prematurely because the low power from the charger (3.4 Watts instead of 5 or more) was causing the batteries to overheat from too much current draw.

My current phone is an iPhone 7 Plus from early 2017. I've had it for four years and nine months. It is just starting to tell me the battery is failing. The average life of rechargeable batteries is around five years when you treat them right. So I'm okay with that... My car charger is a good one! I need a new phone case and new battery, so maybe I need a new phone, or at least a kit from iFixIt and a new case. Decision time...

TriX Loc: Raleigh, NC

The amount of current a USB port can supply is limited by the type of USB port (newer ports are spec’d for higher 5V current) and what the device with the port is designed to supply - many devices will not supply more than a few mA.

As for the car cigarette lighter or USB port, it depends on the vehicle - many vehicles disable the port and lighter unless the key is in the car and either in accessory or on position. In the case of the respondent above who had his vehicle battery die, it wasn’t the phone. With the key in either accessory or on position, other systems in the vehicle were drawing power also. The charging current for a phone isn’t high enough by itself to drain a fully charged battery. Some vehicles like mine, have a safety circuit preventing the battery from being discharged below what is necessary to start the car no matter what you leave on.

As for the 12V outlet “putting out “too much current”, that’s a misunderstanding of basic electricity/electronics. The 12v (or any other outlet) only supplies as much current as the device plugged in draws (as Bill mentioned above)

Longshadow Loc: Audubon, PA, United States

1. The USB port doesn't put out enough current.
- Really? how does one know? Sounds like an opinion... Charging my phone/tablet in the car work just fine. However, the capability of various ports MAY be different.

2. The 12v outlet puts out too much current.
- Really? The ports put out voltage, current draw depends on how much the connected device needs/uses.

3. If the car isn't running, you can kill the car's battery. Considering the size of the car's battery vs the cell phone battery's, I wonder.
- Eventually? Overnight? My USB ports shut off when I turn the car off. The drain is probably no worse than one incandescent light bulb. NOT going to drain the battery in minutes.

I would not put that much credence in the source.

But hey, everyone on the internet is an expert, right?

JBRIII

Maybe the car battery was already weak or using the port means something else was also on. If the accessory position was used to keep the charger on, then other things could easily have been draining power, radio, fans, etc. I have drained car batteries due to leaving the overhead light on by mistake. Big power blocks run maybe 30,000 mAH at 5 volts. Car batteries are often 700 Amps at 12 volts, they can melt a steel bar if shorted out, I would think that unless we are all missing something, you could easily charge dozens of phone without any problem. People run telescopes with accessories (cameras, dew heaters, guide system, etc.) all night off car batteries, something was amiss there I suspect.

burkphoto Loc: High Point, NC

FUD, right? (Fear, uncertainty, and doubt spread mischievously).