How long will a 6V battery power an MP3 player drawing 30 mA of current?

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Discussion Overview

The discussion revolves around the duration a 6V battery can power an MP3 player that draws 30 mA of current, as well as the power consumption of the MP3 player. It includes calculations and considerations regarding battery capacity and theoretical versus practical performance.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant asks how long a 6V battery with a capacity of 600 mA-hr will last when powering an MP3 player that draws 30 mA.
  • Another participant provides a general example of battery duration based on current draw and capacity, questioning the formula for power calculation.
  • A participant asserts that the power formula is Volts multiplied by Amps, correcting a previous misunderstanding.
  • A later reply calculates that the battery could theoretically last 20 hours and provides the power consumption as 0.18 Watts, noting that this is an optimistic scenario due to potential voltage drop during discharge.

Areas of Agreement / Disagreement

Participants express differing views on the calculations and assumptions regarding battery performance, with no consensus reached on the practical implications of the theoretical calculations.

Contextual Notes

The discussion highlights the ideal versus practical performance of batteries, with considerations of voltage drop during discharge not fully resolved.

the_d
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A MP3 player is powered by a 6V battery pack that can supply 600mA-hr of current. If the MP3 player draws 30 mA of current, how long will the battery last before it needs recharging? and What is the power used by the MP3 player?

if any1 can help i'd appreciate it
 
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If a battery has a 1A-hr capacity, and you draw 1A from it, how long will it last? Also, do you know the formula for calculating power from voltage and current?
 
it would last 1-hr. isn't the formula for power current over voltage?
 
Ummm, no. The formula for power is Volts x Amps = Watts.
 
ok thanks ....
 
the_d said:
A MP3 player is powered by a 6V battery pack that can supply 600mA-hr of current. If the MP3 player draws 30 mA of current, how long will the battery last before it needs recharging? and What is the power used by the MP3 player?
if any1 can help i'd appreciate it
t = 600 mA-hr/30 mA = 20 Hours (optimistic, but theoretically correct)
P = .03A x 6V = .18 Watts (as long as the battery holds at 6 Volts)
E = .18W x 20Hr x 3600 sec/hr = 12,960 Watt-seconds (Joules)
Practically, the battery won't hold at 6 volts during the phases of its discharge, so the above calculations are only the ideal case.
-Dr. Bob
 

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