Thread: Automotive electrical question

To those guys who know:

I've wondered for some time if it drains an auto's battery if you leave a cell phone charger plugged into the cigarette lighter when you don't have the cell phone charging. Is that a bad thing to do? When I'm not actually charging my cell, I unplug the charger, but I wondered if this was necessary.

Chris L

Its not necessary since when the phone isn't plugged the energy draw on the battery is none to practically non existent, depending on the style of charger! I leave mine in all the time and have no problems!

Drain depends on your particular charger's design. If the charger has "overcharge" circuitry then it has drain. Usually not enough to worry about. Lacking a spec sheet, an ammeter (DVM) would tell you how much. (load/no load condition, supply side)

It's always a good idea to unplug it when not in actual use just to avoid any possible short on the output plug.

Originally Posted by Sticky

t's always a good idea to unplug it when not in actual use just to avoid any possible short on the output plug.

Sticky has a point, but if you follow it to its logical conclusion you might as well disconnect your battery every time your not using your car!

I know people who do that by the way!

I remember right, this question came up at the dealership one time like 6 years ago... If I remember my facts correctly on a 550 amp hour battery it would take like 6 years for a cell phone charger to drain the battery or some such ridicules number!!!!! in other words a Long Time.....

I don't know about cell phone charger specifically but I have left a CB plugged into the lighter for to long. Even though the CB was off the voltage converter or capacitor or whatever is in a power plug was drawing a little current. This caused heating the burned out the plug. Battery fine, device fine, fuse blown and plug wiring fried. I have no idea how this happened, or how close I might have come to a vehicle fire, but now I unplug everything when I'm not using it.

Originally Posted by Wildtim

I don't know about cell phone charger specifically but I have left a CB plugged into the lighter for to long. Even though the CB was off the voltage converter or capacitor or whatever is in a power plug was drawing a little current. This caused heating the burned out the plug. Battery fine, device fine, fuse blown and plug wiring fried. I have no idea how this happened, or how close I might have come to a vehicle fire, but now I unplug everything when I'm not using it.

This is however probably the "Intelligent" thing to do!!!!!!!! I did not take into account any wiring issues with the answer I gave above.....

My charger has a led that indicates there's power, so in my case there is battery drain... but it's minute in comparison to all the circuits in the car that are also "on" all the time. If you're worrying about the charger causing a dead battery, don't.

However, I unplug mine and stow it in the glove compartment whenever I'm not using it. I figure if I'm in a serious accident the less "loose" things I have flying around in the car the better. Also, I once had my car broken into (window smashed) and the police said the thief probably saw the charger plugged in and figured there was a cell phone plugged in and stowed under the seat (which is where the end of the wire had migrated... I had the cell phone with me). YMMV

You won't run the battery down any great amount if you're driving the car on a regular basis. If you let it sit for weeks on end, it's possible that it might run down the battery a bit.

My cell phone manual says not to recharge the phone using the car charger unless the engine is running, but I've done just that lots of times and have had no problems, but I use the car usually at least 45 minutes per day 5 days per week.

Most recent vehicles have all sorts of electronics powered 24/7 with the ignition turned off... not a problem unless you leave the vehicle sitting for weeks on end. Second to that, most vehicles I've driven over the past 10 years or so actually turn off the cigarette lighter and accessory sockets when the key is removed from the ignition. In any event, the power draw from a car cell phone charger is very minimal.

Regards

Christian