How Long Will a Device Drawing 8mA Last on a 12V Battery? Learn the Answer Here!

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Discussion Overview

The discussion revolves around calculating the duration a device drawing 8 mA will last on a 12V battery with a capacity of 25 mAh. It includes considerations of battery specifications, voltage, and current relationships.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant calculates the duration as 3.125 hours by dividing the battery capacity (25 mAh) by the current draw (8 mA).
  • Another participant confirms this calculation.
  • Questions are raised about the availability of a watch battery that can provide 12V and the typical voltage of watch batteries, which are usually around 1.5V.
  • Concerns are expressed regarding the feasibility of packing multiple cells into a watch battery to achieve 12V.
  • A participant suggests that the question should clarify the voltage's role in the calculation, proposing a rephrased version of the original question.

Areas of Agreement / Disagreement

Participants generally agree on the calculation method for determining battery life, but there is uncertainty regarding the existence of a 12V watch battery and the typical specifications of watch batteries.

Contextual Notes

There is a lack of consensus on the characteristics of watch batteries, particularly regarding their voltage and capacity, which may affect the discussion's conclusions.

david90
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How long will a device drawing 8 mA last on a 12 v bat that has a 25mAh?


25/8 = 3.125 hours?
 
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You got it.

- Warren
 
is there a bat as small as a watch bat that can produce that much mAh at 12v?
 
Not that I know of.

- Warren
 
what is ur mAH for watch bat?
 
Hell if I know, but I've never seen a 12V watch battery. Most battery chemistries in use today are 1.5 volts or so -- they'd have to pack 8 cells into that watch battery package to get 12V, and I don't think it's been done.

- Warren
 
Electrical current and pressure

david90 said:
How long will a device drawing 8 mA last on a 12 v bat that has a 25mAh?
Voltage is electrical pressure, and it is analogous to water pressure. We don't need to know what the voltage is to answer this; we just need to know that it is considered consistent throughout the problem. The question should be stated as:How long will a device drawing 8 mA at a particular given voltage last on a battery that has a capacity of 25mAh at the same given voltage?.



25/8 = 3.125 hours?
Yes, if the question is stated as I corrected above.
 

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