How many milliamps (mAh) does the GPS in Google Maps take up?

Discussion in 'iPhone' started by travelbug22, Jan 23, 2011.

  1. macrumors newbie

    Jan 23, 2011
    I’m curious, how many milliamps does the iPhone 4’s GPS take up when running Google Maps GPS for an hour?
  2. macrumors member

    Jun 30, 2010
    It uses roughly 4 mA.

    GPS in the iPhone 4 is a Broadcom BCM4750 which is spec'd at less than 15 mW. Assuming 15 mW power consumption with a 3.7V battery that works out to 4 mA.
  3. thread starter macrumors newbie

    Jan 23, 2011
    Thanks that info. I wonder how much of that 4 mA sucks out of the 1420mAh battery in an hour....
  4. macrumors regular

    May 16, 2010
    Fareham, UK
    The clue's in the name :rolleyes:

    However, the 4mA figure isn't very useful on its own. By using the GPS you may also find that other components can't go to sleep, thereby increasing battery draw significantly more than the 4mA figure.

  5. macrumors demi-god


    Apr 20, 2009
    He, he,......assuming that the 4ma is correct (another discussion) 4mA in an hour is 4mAH. :D
  6. thread starter macrumors newbie

    Jan 23, 2011
    Ok, I'm a rookie at learning electric terminology. I had no idea the 4mA would be pulling 4 milliamperes in an hour.
  7. goosnarrggh, Jan 23, 2011
    Last edited: Jan 23, 2011

    macrumors 68000

    May 16, 2006

    A milliampere (mA) is a rate of electrical current flow through one specific crossectional point in a wire.

    One ampere (A) is equal to one one Coulomb of electrons passing through the wire per second. (One Coulomb of electrons is equal to approximately 6.2415e18 electrons.)

    One milliampere (mA) is equal to one thousandth of of an ampere, or one thousandth of one Coulomb of electrons passing through the wire per second -- approximately 6.2415e15 electrons.

    If you have a 4 milliampere flow, then you have 4 thousandths of a Coulomb of electrons passing through the wire each second. If that flow is sustained for 1 hour (3600 seconds), then a total 14.4 Coulombs of electrons have passed through the wire -- or approximately 89.878e18 electrons.

    Milliampere-hour (mAH) is a convenient shorthand way of expressing the total number of electrons that have flowed over time, and it is expressed as the product of the rate of flow in mA, multiplied by the duration of time in hours. Since we're multiplying a flow in units per second (mA), by a duration in hours, the resulting expression has been somewhat abstracted away from the original physical meaning behind the elementary units, and it would need further conversion if you wanted to get back to the elementary units. But it happens to be a convenient way of calculating electrical consumption in a lot of real-world scenarios without having to carry around too many superfluous digits of precision. (Nobody talks about their battery's stored energy capacity in terms of Coulombs.)
  8. macrumors 68030


    Sep 8, 2003
    Scuby in this case is also quite right that the 4mA by itself isn't terribly useful. Electronics are complex beasts these days, and a device will do all sorts of things to save electricity when it can pull it off. You are almost better off measuring the power drain of the whole system when it is doing one thing, versus another. It is possible to measure this drain, but it requires some equipment. Something along the lines of something that can measure the current and power going through a 12VDC car outlet plug. And then hook a fully charged iPhone up to a car power adapter and watch the power drain. It isn't precise, but it is close enough for most purposes us consumers could have. A bit like a 12VDC version of a Kill-a-watt. The camping battery I built awhile back has one built in so I can see the level of drain I'm placing on it and ensure it will last the trip.
  9. macrumors 68000


    Jul 2, 2009
    1.21 Jiggawatts. No wait.. that's my flux capacitor.
  10. thread starter macrumors newbie

    Jan 23, 2011
    Awesome, thanks for that review, it filled in a lot of gaps of information I had missing in my head.

    The whole reason I originally asked how many milliamps does the iPhone 4's GPS takes up is because in an attempt to improve my iPhone 4’s battery performance on an upcoming NYC trip, I started to look for external battery extender solutions. One of these first solutions I came a crossed was the New Trent IMP800 that advertised 8900 mAh, roughly 6.2 times more than the iPhone 4 battery (1420 mAh). So, immediately I assumed an mAh (milliampere-hour) is a measurement of how much power a battery possesses, and therefore I was curious how much the GPS signal takes up when it’s actually initiated.

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