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Does Phone Charger Drain Car Battery?

Puzzled88Puzzled88 Registered User Posts: 1,120 Senior Member
edited April 2011 in Parent Cafe
My H and I are debating this question. His car battery is dead and he just returned from a 12 day trip, during which his car was not driven and the Iphone charger was left plugged into the lighter socket but without a phone connected. I think it drained the battery. He says no. Does anyone actually know the answer? An educated guess? A totally unsubstantiated opinion?
Post edited by Puzzled88 on

Replies to: Does Phone Charger Drain Car Battery?

  • tango14tango14 Registered User Posts: 1,578 Senior Member
    On our Toyotas you cannot charge when the engine (or Acc) is not on. So leaving it plugged in would have no effect. However, I drove a rental car (it was a Ford or Chevy) where it charged whether anything was turned on or not. I don't know what effect leaving the charger plugged in would have vs. actually charging the phone. I know it still draws power even when not charging, but I don't know how much.
  • notrichenoughnotrichenough Registered User Posts: 8,000 Senior Member
    Chargers can draw power if plugged in, even if not attached to the device.

    Is it enough to drain a car battery in 12 days? Maybe.

    If it draws 1 watt of power, x 24 hours x 12 days, that's 288 watt-hours. 2 watts, 576 watt-hours. 3 watts, 864 watt-hours.

    A car battery holds around 800 watt-hours of power.

    So depending on phantom load of the charger, it could drain the battery enough that it cannot start the car, or even completely drain it.

    If the car battery is old, it may not be holding a full charge any more, either.
  • FlyMeToTheMoonFlyMeToTheMoon Registered User Posts: 2,586 Senior Member
    We had the same suspicion many years ago with our Ford Freestar. The battery was dead, and the only thing we could attribute it to was the fact that the phone charger was plugged in. No phone was charging. We decided not to take a chance in the future, and always make a point of unplugging the charger when we turn off the engine.
  • dadxdadx Registered User Posts: 2,579 Senior Member
    Many cars have lighter sockets that are off when the car is off. In those cases, there is no way to draw current from the battery.

    Also, most chargers do not draw any current unless there is a phone attached to them.

    The biggest cause of battery failure is an overhead light left on (map light or door related light that is on because the door is ajar). And sometimes, when the battery is getting older and the car is not driven much, it simply gives up the ghost on its own after a period of inactivity. My experience has been that after 3-4 years, the battery is pretty vulnerable. After 4-5 years, it will definitely decide at some point to cease performing its duties.
  • SweetTeaSweetTea Registered User Posts: 306 Member
    Our AAA service providers (different ones) have told us that yes a charger plugged in will drain the battery. We believe if the battery is older that is more likely to have an effect but we were told that even a little trickle over time causes your battery to die sooner so we have been better about unplugging for now. It took us awhile to change our habits as we had two batteries that died after a prolonged time away and the charger had been plugged in.
  • Puzzled88Puzzled88 Registered User Posts: 1,120 Senior Member
    How marvelous to have a panel of experts available at all hours. I've sent him your replies. It is the original battery on a 2006 car. Now that AAA has started it up, it's giving him odd service lights and messages - funky power steering, a warning that his wiper blades may go rogue, and something about the battery. He's going to take it into the dealership tomorrow. Many thanks to all of you.
  • colorado_momcolorado_mom Registered User Posts: 8,396 Senior Member
    We had a car sitting outside for several weeks without being driven. We are not sure if the battery died to just sitting in the cold or the battery charger.

    The Sears Diehard battery was over three years old, so we were ready to replace it. But when my husband took it out (not an easy chore on this model) and took it down to Sears, it tested fine. They recharged it for free and that fixed things.

    I was also impressed that on the phone the Sears tech volunteered to hear our symtoms and give advise. If they had told us the battery was bad, we would have believed them. So kudsos for honesty at Sears!
  • ellemenopeellemenope Registered User Posts: 11,380 Senior Member
    Who knew...I sometimes leave my phone charger in the lighter socket. I think maybe I'll change that, just in case.
  • colorado_momcolorado_mom Registered User Posts: 8,396 Senior Member
    ellen - I bet you're fine with the car charger plugged in, especially if you are driving the car a lot. I can't convince myself that it would drain the battery much without a phone attached.
  • notrichenoughnotrichenough Registered User Posts: 8,000 Senior Member
    I can't convince myself that it would drain the battery much without a phone attached.
    It's called 'phantom load', and refers to any electronics device that draws electricity when not in use.

    It can include chargers of all kind, TVs, computers, appliances, etc.

    There are estimates that up to 15% of the electricity you use in your house is wasted by phantom loads.

    If you are driving the car regularly you will be ok because a charger will not drain the battery in a day, and the battery gets recharged while you drive. But over a couple of weeks, it can happen. See my power calculations above.
  • dragonmomdragonmom Registered User Posts: 5,644 Senior Member
    I know that my old Ford mini-van would continue to charge my phone after I turned the car off, so that socket was always on. My new car doesn't, which annoying if I get somewhere and discover my phone is dead, but I guess not as annoying as finding my car battery is dead.
    notrichenough is right, we waste huge amounts of electricity to "vampires" - ie, chargers and other "turned off" electronics. If the little red light is on, it's sucking power. Not much, but if you walk around your house and count all the little red lights/clock/displays - it's a huge waste.
  • davh01davh01 Registered User Posts: 229 Junior Member
    Depends on you socket if it can deliver power or not. Assume that it does, now it also depends if your cell phone plug draws a current or not. If the plug has a light, then it definitely can drain your battery. Otherwise, it is just an open wire (open circuit) and will not drain battery.

    Other things in the car may draw current (radio, alarm, etc). If the battery is weak, it may not recharge sufficiently and can cause the battery not have enough power to start.
This discussion has been closed.