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Cell Phone / Small Electronics Amp Usage

  1. Jul 1, 2015 #1
    Hello everyone. After googling my eyes out, the only hits I get are about people wondering how much to charge their cell phones. I'm looking for a more academic view point on this. My question is this...

    Cell Phones, like any device require power. I'd like to find out how many amps or miliamps that similar devices need. Things like cell phones, tablets, laptops, etc... What's the average ampere's that the device itself draws? Over how many volts? I ask because I'm always seeing cell phone and tablet's rated in Miliamp hours. Why is this? For example:

    Nexus 6: Battery 3220 mAh So I know that miliamps are 1000th of an amp. So the battery for this device spits out about 3.2 amps. Is 3.2 amps very high for a small device?
    Or does this means that it's 3.2 amps spread out over an hour? Where can I find out how many amps and volts the device itself requires, rather than how much the batter provides?

    THanks everyone
  2. jcsd
  3. Jul 1, 2015 #2


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    Most modern battery powered devices have very aggressive power saving modes so its hard to say exactly what the power draw is unless you know what is running on the device and how its configured. So 3220 mAh could be an hour with heavy game use or 10 hours depending on what you do.
  4. Jul 1, 2015 #3


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    Your question and misunderstanding is a very common one and we see the similar Q at least once a week on the forums

    batteries are rated in mAH or AH milliamp Hour or Amp Hour

    so say your battery is rated at 1000 mAH ( =1AH) That means it can supply 1000 mA for 1 Hr or 500mA for 2 Hrs. Keep in mind, that is for a perfect battery ( which of course don't exist ) so you may not get that exact 1 Hour or 2 Hours etc

    The amount of actual current drain at any given time for say your mobile phone will depend on how heavily its being used
    just sitting awaiting for a call ( screen dimmed) playing games or videos, WiFi running as well
    All these added things will increase the current drain

    so relate that to your stated 3.2AH battery

    Last edited: Jul 1, 2015
  5. Jul 2, 2015 #4
    Thanks for the replies. So because cell phones have such a wide amount of 'current drain', is this the reason why in the Cell phone specs, they provide how much the battery can supply, rather than providing how much the cell phone requires? Because it would be too variable depending on what you're doing?
    Can't they provide at least a 'basic' amp and voltage needs for the device?

    Also is there a difference in 'sensitivity' in devices? What I mean by this, is that do devices and circuitry more tolerant of a flux in voltage or a flux in amps? For example, if a device requires 0.5 amps at 5volts. Would a small spike or dip in amps, be more detremental, or would a small spike or dip in volts be more harmful?
  6. Jul 2, 2015 #5


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    Cell phones have regulators that smooth out minor changes in battery voltages from changes in power consumption.

    Some old information but not much has really changed.
  7. Jul 3, 2015 #6


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    The power system of a battery powered device is designed to deal with the normal variation in battery voltage as the battery discharges. So there is no need to think about that aspect.

    Rating or judging a device by its battery capacity (mah) is common, but largely meaningless. A device with a 1200mah battery will last just as long as a device with a 2400mah that draws twice the current. You have no way of knowing the details of how much energy a specific device requires to do a given action.

    What you really need to consider is a device's battery life for different operational scenarios. Playing a video, listening to an audio file, listening to streaming over cellular, talk time, video demands of games being played, etc etc.

    It is not easy for a consumer to judge which device will provide the longest time between charges given how he wants to use the phone. You have to depend on review sites that compare different devices under similar scenarios.
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