# could cell phone charge drain car battery?



## oh'mike (Sep 18, 2009)

I forget to unplug my charger and never had an issue with it draining the battery noticeably--

My truck battery is about 11.25 volts at rest--and 14 volts when the truck is running---


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## joed (Mar 13, 2005)

A cell phone will not drain a car battery. The on board computer draws more power than the cell phone charger would.


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## 95PGTTech (Jun 24, 2014)

noquacks said:


> Heard it could, especially if you leave it charging while car is "off", as in not being driven/engine off, of course. Seems like a cell phone wouldnt need so much voltage, sheesh. Is this true, people?
> 
> Also, does a car have to be with engine on for same voltage to "seep" into the cell phone to charge it? The cigarette lighter I understand is always on the ON position, so shouldnt it be emitting the same voltage weather the engine is on/off, sine lighter terminal is always ON?
> 
> Thaks


It's all about the amps. Yes, it does drain the battery. Does it do it to any meaningful level? Being that most USB chargers are 1A or 2.5A, no. The radio and PCM keep alive memories are both a greater amperage. It's not a good idea to leave any load on a car battery without the charging system running.


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## Anti-wingnut (Oct 18, 2009)

And unlike a house hold charger, an automobile charger won't drain the battery if the phone is not plugged in


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## noquacks (Jun 5, 2010)

Big thanks, people. So, I figured that had to be bogus scare type info- but Im still not clear on this: is the same amount of charging "power" available to a phone being charged the same as that of same terminal (cigarette lighter) while engine is running? Isnt the lighter terminal a steady voltage output- car on or car off??

In other words, if my phone needs lets say 4 hours of charge with car off, will it be charged in less time if car is running/engine running?

thanks


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## Bob Sanders (Nov 10, 2013)

Your voltage is higher with the engine running. While the battery is 12 volts (slightly less actually), the alternator (while turning) will put out anywhere between about 12.5 volts to 14.5 volts.

This shouldn't make too much of a difference with your usb charger though since the voltage is chopped at 5 volts.


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## PD_Lape (Nov 19, 2014)

joed said:


> A cell phone will not drain a car battery. The on board computer draws more power than the cell phone charger would.


I agree. It should not drain car battery. If your battery keeps on draining for whatever reason you should probably have it checked.


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