A mobile telephone is supplied by a Li-ion secondary battery whose capacity (in

Question

A mobile telephone is supplied by a Li-ion secondary battery whose capacity (in the fresh stale) is 1200 mAh. The technology used means that this capacity is practically unchanged regardless of the discharge current rate. Standby mode consumes 1.7 mA. Conversation mode consumes 65 mA in GSM operation and 220 mA in 3G operation. For each of these modes of operation, we shall take the consumption to be constant. What is the range (in hour/days) of such a telephone in GSM operation and then in 3G operation if it is in "conversation" mode for 5% of the total time?

Explanation / Answer

Answer:- The meaning of 1200mA is, if 1 mA current is drawn from battery then battery will run for 1200 hour.

Now for standby mode current drawn is, Is = 1.7 mA, hence battery running time in standbymode, Ts = 1200/1.7 = 705.8823 hr

similarly for GSM mode, IGSM = 65 mA, hence TGSM = 18.4615 hr and 5% of TGSM = 0.9230 hr

for 3G mode I3G = 220 mA, hence T3G = 5.4545 hr and 5% of T3G = 0.2727 hr

to calculate total standby time after conversation we write as-

0.065x0.9230 + 0.220x0.2727 + 0.0017xT = 1.2

hence T = 635.3 hr

so range of such telephone is = 635.3 + 0.2727 + 0.9230 hr = 636.4962 hr = 26.52 days .

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