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Power consumption of mobile phone in watts

Discussion in 'Electronic Design' started by [email protected], Mar 8, 2007.

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  1. Guest


    I'd like to find out the power consumption of a mobile phone in watts.
    I've got the following info:

    "Maximum Power Capacity (Watts) 3.7V Li-Ion 760mAh"

    Would this mean that the power consumption of the phone is = 3.7*0.76
    = 2.812W?

    If not, could someone please direct me to some links where I could
    find the power consumption of a typical mobile phone?

  2. GregS

    GregS Guest

    probably about half that.

  3. GregS

    GregS Guest

    it would also depend on the transmit power which changes depending on

  4. No, that means the battery capacity is 2.812 Amp-hours of capacity. At 3.7V
    that's 10.4 Watt-hours of energy.
    To find the power consumption you need to know how much current the phone
    draws in Amps. You then multiply that by the 3.7V and you will know how
    many Watts it is using. I can tell you this though, it's going to vary over
    a large range from milliwatts to more than 5 Watts at times.

    You could use talk time to work backwards and determine average power usage.
    If you have a 10 hour talk time, then the phone is dissipating an average of
    (10.4watt-hours/10hours) = 1.04W. This would equate to an average current
    of (1.04W/3.7V) = 281mA of current. We can verify this by taking current *
    voltage * time to come up with the energy requirement. .281A * 3.7V *
    10hours = 10.397 Watt-hours the capacity of our example battery.
  5. Depends on how long you can use it without a re-charge.
    So it is 2.8 W / hour, means it can consume 2.8 W for 1 hour,
    1.4 W for 2 hours, etc.

    Also the mobile (GSM) phone transmit power depends on the signal strength,
    distance from the base station.

    And it transmit it of course uses a lot more power then in standby.

    You phone specs should tell you how long it can standby and how
    long it can transmit, say if the max transmit (speak time) is 2 hours,
    then it uses 1.4 W minim during transmit.
    If you can talk 4 hours it uses .7W to transmit.
    If it has 100 hours standby time, then it uses 28mW in standby.

    Hope you can follow the math.

    If it dont workatall battery empty.
  6. Tim Shoppa

    Tim Shoppa Guest

    I don't have any idea why it says (watts) on the label.

    3.7V * 0.76 Ah = 2.8 Watt-hours.

    If the battery powered the phone for one hour and then went dead, then
    the phone used up an average of 2.8Watts for that hour.

    More typically that battery will be good for several days of
    operation. 4 days = 100 hours which would mean average power
    consumption of 0.028 watts.

    Note I said average.

    In real-life, the power consumption is very peaky. The phone will not
    be regularly transmitting unless a call is in progress. Most phones
    will also be in high power consumption if in idle in a fringe area or
    if it's constantly searching for service in a non-service area. (Many
    modern phones have a "power-save" option for the latter case).

    It might be drinking a good fraction of a watt during a phone call if
    you are in a fringe area.

  7. Oops, let's try again. The battery capacity is as specified 760mAh. The
    amount of energy is 2.812Watt-hours.

    an average of (2.812watt-hours/10hours)= .281W. This would equate to
    an average current of (.281W/3.7V) = 76mA of current (a highly suspicious
    value). We can verify
    requirement .076A * 3.7V * 10hours = 2.812 Watt-hours
    Sorry for the stupidity.
  8. mpm

    mpm Guest

    It is a certainty that the cell phone industry uses every trick in the
    book to maximize the battery life of portable cell phones. The
    various air-interface standards (Analog, GSM, GPRS, Edge, CDMA,
    etc...) all go to great lengths to minimize current consumption by
    incorporating various power-saving features into the cell phones and
    into the air interface signalling being used.

    For example, when "ringing" a cell phone, the base station will use a
    specific timing sequence which will allow the cell phone receiver to
    go to sleep for the majority of the time it is not actively engaged in
    communication. (In analog, this was the Overhead Message Paging
    Channel, or something to that effect.) BTW - This is also related to
    how the cell site "knows" which particular cell site to use to contact
    the subscriber, and relates to cell site capacity issues.

    Essentially, the base station will send out a synchronization preamble
    (or its equivalent), and the phones will "wake-up" periodically, sync
    and listen for their ID. If no match, then back to sleep.

    Note: This is a gross over-simplification of a very complex signalling

    Now, for transmit:
    In all air-interface standards I'm aware of (for PCS and Cellular
    anyway), the base station controls the RF Output power of the cell
    phone. If the cell site is having trouble "hearing" the phone (i.e.,
    low received signal at the cell site), it will instruct the cell phone
    to increase its RF output within certain limitations. If this doesn't
    solve the problem, the cell site will terminate the call. Similary,
    if the cell site has too much signal from the mobile phone, it will
    instruct it to turn down its transmitter power (to save battery life
    AND more importantly, to avoid overloading the cell site's RF receiver
    distribution amplifier systems - which are shared by all users using a
    particular cell site.)

    There are many reasons signal can change at either end during a call,
    which I won't get into now.
    The point is: the phone's RF Output power may change many times a
    second during a typical call.

    Note: Again, this is an over-simplification of a very complex
    signalling scheme.

    To make matters more interesting, the cell site's output power may
    also change.
    This can be caused by active (non-linear) cell site transmitter
    combining where the more channels (or carriers) are connected
    (dynamically) to antennas, the fewer watts are available for
    individual channels or carriers on the air.

    Another factor is dynamic frequency re-allocation of the cell
    provider, which may cause the cell site frequencies and coverage(s) to
    change dynamically with use. In other words, overloaded Cell Site
    -"A" might "borrow" some idle bandwidth from an adjacent (available)
    Cell Site "B". Because of RF intermodulation and co-channel or
    adjacent channel interference issues, this can also affect RSSI and
    cell site performance -- It's a non-optimal solution to congestion,
    but it's better than dropping the call.(?) I don't know how wide
    spread the practice of dynamic allocation is, but you can reasonably
    expect it in conjested areas, or in areas that have infrequent,
    periodic usage demands - such as sports staduims, etc...

    And note: This is all transparent to the average user.
    Except perhaps the "4-bars" or "5-bars" discussions people sometimes
    This is usually an indication of the strength of the signalling
    channels, NOT the voice channels.
    So if the Cell Provider amps up their messaging channel transmitters,
    this can give a false sense of performance. (I have seen this only
    one time, and I won't name names.) But this can be one explanation
    why you sometimes can't make a call even though you have 4-bars of
    signal. (And more likely, the reason is one of several dozen other
    things that can go wrong, which is too much to get into here.)

    If you want to do some more research on battery-saver features of air
    interface signalling schemes, I would suggest starting with a much
    simpler one. Do a google search on "POCSAG", or "GOLAY", which were
    two widely used signalling schemes used with Pagers (beepers).

    These will be "simpler" because those devices operated in a
    predominately one-way fashion.

    Do you see now why you can't go by the battery nameplate?
  9. Rich Grise

    Rich Grise Guest

    No, it means that the energy consumption is 2.812 watt-hours. How long it
    will last depends on the actual wattage used, which is the rate of using
    energy, using up the charge from the batteries.

    To find actual power consumption, break the battery circuit and interpose
    an ammeter (or milliammeter, just be sure it has a high enough range,
    although it's a sure thing it's less than 2.8A, if the phone lasts an
    hour), and measure it, in real-time. A cute way to insert an ammeter into
    a circuit where the batteries are in spring-loaded holders is to take
    two little brass strips, separate them with a piece of stiff paper, and
    stick the little sandwich between the battery post and contact. Then
    put the ammeter (or a switch! :) ) from one brass strip to the other.
    Try going to and put "power consumption of a typical
    mobile phone" in the search box, with or without the quotes - have an
    adventure! :)

    Good Luck!
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