How much current does a cell phone use?

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Discussion Overview

The discussion centers around the current usage of cell phones, specifically comparing it to historical batteries like the voltaic pile. Participants explore various factors affecting current draw, including battery specifications, usage scenarios, and the impact of background processes.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant seeks to compare the current output of a voltaic pile to that of a typical lithium-ion battery in a cell phone, noting the voltaic pile's limitations in current delivery.
  • Another suggests estimating battery current by dividing the AmpHour capacity by the battery run time, while acknowledging that this estimate may vary significantly due to factors like signal strength affecting power draw.
  • A participant mentions the Simcom SIM900 GSM module as an example, indicating it can draw over 2 A during initialization and typically 250 mA, though this may not represent all devices.
  • One contributor provides specific battery specifications for their phone, calculating an average current draw of 500 mA during use, while noting that instantaneous current can vary based on activity.
  • Another participant shares findings for an iPhone 4, estimating average current usage of 100 mA for phone calls and 140 mA for Wi-Fi, while contrasting this with the limited output of a voltaic pile.
  • Several participants report current readings from an app, with values fluctuating between 300 mA and 600 mA, suggesting that background processes may influence these readings.
  • There is mention of the phone's background activities, such as checking for updates and maintaining connectivity with cell towers, which may contribute to variations in current draw.

Areas of Agreement / Disagreement

Participants express varying estimates of current usage, with no consensus on a definitive value. Multiple viewpoints on how background processes affect current draw are presented, indicating ongoing uncertainty in the discussion.

Contextual Notes

Participants acknowledge that current draw can vary significantly based on usage scenarios, signal strength, and background processes, which complicates the ability to provide a single, accurate measurement of current usage.

Cool4Kat
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I am doing a series of videos on the history of electricity and I am working on a video on Volta and the first battery.

Anyway, I want to compare the voltaic pile to a typical li-ion battery running my iPhone. Now the voltaic pile could easily create 20 V of potential but it had high internal resistance and would max out at around 15 mA of current.

I can easily find the voltage of the battery but I have no idea how much current it regularly uses! Nor do I know how much it needs for high power items like downloading pictures. Any help? Any idea where I could find the answers? Thank you so much!
 
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See if you can find a third-party supplier of replacement batteries and hope they list battery AmpHour (AH) capacity. (You might get lucky and be able to get that info from a phone dealer or distributor, but don't hold your breath!) When you find that, look at the advertising or user manual for the phone to find the battery run time, in hours, between charges. Divide the battery AH capacity by the run time to estimate the battery current. The estimate will be off by a factor of two to four, could be either high or low (thanks to advertising and battery life considerations.)

Another confounding factor is if the phone is receiving a weak (or no) signal from the cell tower it transmits at maximum power, drawing more current. Conversely, with a strong cell tower signal it will reduce transmit power to conserve battery charge

Now you've got me curious, when/if you find an answer please let us know the estimate in a followup post here.

Tom
 
Google for power requirements of the Simcom SIM900 - GSM module that could be used in simple DIY electronics projects. While it doesn't have to be representative of all similar devices, it is definitely an example of them.

I can't find the datasheet at the moment, apparently there were some shifts in the ownership, sites moved and most links I stumble upon are broken. If memory serves me well it can draw more than 2 A during initialization, 250 mA typically (whatever it means) and some single mA in sleep mode.
 
The battery in my cell phone is 3.7 volts at 2100 milliamp-hr (2.1 amp-hrs). That will last for, IDK, maybe four hours of continuous talking. The average current would then be 2100 mah / 4 hours = 500 milliamps. The instantaneous current will be higher when transmitting, and lower when receiving. This is a SWAG, somebody else may have better numbers. But at least it's better than a WAG.
 
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I followed Tom's advice and looked up the specs for a phone this is what I got:

I found the specs for the iPhone4 (admittedly a little behind the times but that is OK). It's battery is 3.7 Volts and has a capacity of 1400mAh. It would provide 14 hours of phone and 10 hours of wifi. So that means, on average, the phone used 100 mA and the wifi used 140 mA. I think I am going to say that a cell phone needs to be able to provide about 150mA of steady current for many hours, and the Voltaic pile can only produce a steady current of like 1 mA (although it can do a maximum of 15 mA but only for like a half a minute). Surprisingly, a little LED light bulb will visibly glow with just 0.1 or 0.2 mA of current so you can't use a stack of pennies to run your phone but you can use it to light up an LED!

I will try to look up more modern specs but they will be out of date in 4 months anyway!
 
I have an obviously named app on my phone that tells me at this second it is drawing 1.8Amps.
 
What’s the name of the app??
 
Cool4Kat said:
What’s the name of the app??
Ampere.
 
This is kinda late but on ampere it says that my phone is draining 300ma, about a minute ago it was 600ma. I am unusre why it changed since I was sitting there staring intently at the amperage on the app, and nothing else
 
  • #10
Stephenk53 said:
This is kinda late but on ampere it says that my phone is draining 300ma, about a minute ago it was 600ma. I am unusre why it changed since I was sitting there staring intently at the amperage on the app, and nothing else
A cell phone is a tiny computer. It is doing all sorts of things in the background. Maybe it was pinging Facebook for updates.
 
  • #11
Stephenk53 said:
This is kinda late but on ampere it says that my phone is draining 300ma, about a minute ago it was 600ma. I am unusre why it changed since I was sitting there staring intently at the amperage on the app, and nothing else

russ_watters said:
A cell phone is a tiny computer. It is doing all sorts of things in the background. Maybe it was pinging Facebook for updates.

Yes, and it is also regularly pinging and being pinged by the nearest cell tower to confirm connectivity, location and ID etc
those little bursts of transmit and receive ... specially the transmit, will increase the observed current usage
 
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