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Energy Consumed while charging a mobile phone

  1. Dec 3, 2015 #1
    The Rating on my Mobile Phone Charger is:
    Input : 100 - 240 VAC
    50-60 Hz 0.15A
    Output : 5.0V ⎓ 1.0A
    How will we determine the energy consumed by the charger in T Hrs?
  2. jcsd
  3. Dec 3, 2015 #2


    Staff: Mentor

    This will be very inexact because rated values are not actual values. By comparison, your car could be rated to drive at 120 mph, but that has nothing to to with speeds you actually drive.

    120V * 0.15 A = 18 Watts, or 0.018 kWh of energy per hour, or 64,800 joules of energy per hour.

    Edit: That does not include energy used in the grid supply chain.
  4. Dec 3, 2015 #3
    A rule of thumb is 20% loss in the charge cycle of a battery. That doesn't count inefficiencies in the charger, etc.

    I would guess a very rough estimate of twice the rating of the battery for a modern charger during active charging. (As opposed to sitting there not charging, but plugged in.)
  5. Dec 3, 2015 #4


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    Science Advisor

    I think Jeff Rosenbury is on the right track. A typical cell phone battery stores about 4 amp-hours at 3.6V = 4.0 * 3.6 * 3600 = about 50,000 Joules. Assuming half the energy is lost during charging as Jeff Rosenbury suggested brings us up to about 100,000 Joules. This is about 0.03 kWh, and costs about 0.3 cents at 10 cents/kWh.
  6. Dec 4, 2015 #5


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    Gold Member

    Never seen a 4000maH cell phone battery. More like 2600 or less is typical.

    Depending on the efficiency of the charger in the phone, you need to
    1. put energy into the battery
    2. deal with the efficiency of the charger circuit in the phone
    3. Run the processor, etc. (maybe)
    4. Deal with the efficiency of the wall wart.

    Most are probably switchers, so that run in the area of 10-20% lost.

    Only way you will ever know for sure is to record the current into the phone during a charge cycle at the wall wart input.

    Here is a charge cycle for an 1800 maH battery. You can see the constant current phase followed by the constant current phase.
    This is just how the battery itself behaves when charged by a charger. (this happens to use 900ma. The next phone might use 400ma. depends on the phone)

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