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Old Jan 23, 2011, 12:05 PM   #1
travelbug22
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How many milliamps (mAh) does the GPS in Google Maps take up?

Iím curious, how many milliamps does the iPhone 4ís GPS take up when running Google Maps GPS for an hour?
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Old Jan 23, 2011, 02:12 PM   #2
dffdce
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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.
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Old Jan 23, 2011, 02:47 PM   #3
travelbug22
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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.
Thanks that info. I wonder how much of that 4 mA sucks out of the 1420mAh battery in an hour....
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Old Jan 23, 2011, 02:52 PM   #4
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Originally Posted by travelbug22 View Post
Thanks that info. I wonder how much of that 4 mA sucks out of the 1420mAh battery in an hour....
The clue's in the name

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.

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Old Jan 23, 2011, 03:12 PM   #5
Givmeabrek
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Thanks that info. I wonder how much of that 4 mA sucks out of the 1420mAh battery in an hour....
He, he,......assuming that the 4ma is correct (another discussion) 4mA in an hour is 4mAH.
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Old Jan 23, 2011, 03:25 PM   #6
travelbug22
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He, he,......assuming that the 4ma is correct (another discussion) 4mA in an hour is 4mAH.
Ok, I'm a rookie at learning electric terminology. I had no idea the 4mA would be pulling 4 milliamperes in an hour.
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Old Jan 23, 2011, 03:57 PM   #7
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Ok, I'm a rookie at learning electric terminology. I had no idea the 4mA would be pulling 4 milliamperes in an hour.
Aside:

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.)

Last edited by goosnarrggh; Jan 23, 2011 at 04:08 PM.
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Old Jan 23, 2011, 05:08 PM   #8
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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.
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Old Jan 23, 2011, 06:17 PM   #9
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1.21 Jiggawatts. No wait.. that's my flux capacitor.
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Old Jan 23, 2011, 06:27 PM   #10
travelbug22
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Originally Posted by goosnarrggh View Post
Aside:

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.)
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 4ís 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 itís actually initiated.
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