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#1 2020-10-12 10:24:18

TyphooNN
Member
Registered: 2020-07-14
Posts: 4

Bad battery performance

Used to buy new battery for my pretty old asus laptop with KDE
But the battery life is horrible, 2h 50min of use with new battery.
So I did a powertop to locate what takes so much power in my system.

https://imgur.com/a/5KAR5G5

When I plug the AC on my discharge rate drops to 8W and 6h of usage.
Why do battery mode consume more power?

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#2 2020-10-12 16:08:27

ewaller
Administrator
From: Pasadena, CA
Registered: 2009-07-13
Posts: 17,463

Re: Bad battery performance

I don't place much faith in Powertop.  It depends on the pseudo file system /sys/class/power_supply/BAT0.  I prefer to look at the content of those "files" directly.  But, those values are dependent on what the smart battery itself reports.

I don't believe your system is running on 8W.    I would believe 50 to 75W depending on back light brightness, CPU load, Disk drive type, GPU activity, and attached USB devices.

And ~3 hr of battery operation is not terribly unreasonable.
How big is the battery?  Is that expressed in Amp-hours, or Watt-hours.  If Amp-hours, what is the battery voltage?
A typical battery is about 5 Ah at 16V, or 230 Wh.  Three hours of life would be 77 W.

While discharging, look around in /sys/class/power_supply/.  Your battery will be called something like BAT0.  There will be a directory for it containing "files" such as current_now, charge_full, charge_now, and voltage_now.
Post the contents of those (noting what files they came from).


Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
---
How to Ask Questions the Smart Way

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#3 2020-10-12 21:46:34

TyphooNN
Member
Registered: 2020-07-14
Posts: 4

Re: Bad battery performance

power_now: 15105000
voltage_now: 15000000
energy_now: 15000000

Didnt find the other one you asked for

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#4 2020-10-15 05:48:24

VDmvKcW9JamBSir5fNfehqpG
Member
From: Earth
Registered: 2019-12-30
Posts: 36

Re: Bad battery performance

ewaller wrote:

I don't place much faith in Powertop.  It depends on the pseudo file system /sys/class/power_supply/BAT0.  I prefer to look at the content of those "files" directly.  But, those values are dependent on what the smart battery itself reports.

I don't believe your system is running on 8W.    I would believe 50 to 75W depending on back light brightness, CPU load, Disk drive type, GPU activity, and attached USB devices.

And ~3 hr of battery operation is not terribly unreasonable.
How big is the battery?  Is that expressed in Amp-hours, or Watt-hours.  If Amp-hours, what is the battery voltage?
A typical battery is about 5 Ah at 16V, or 230 Wh.  Three hours of life would be 77 W.

While discharging, look around in /sys/class/power_supply/.  Your battery will be called something like BAT0.  There will be a directory for it containing "files" such as current_now, charge_full, charge_now, and voltage_now.
Post the contents of those (noting what files they came from).

The principle is right, but your details are wrong, 5Ah at 16V is 80 WHr, not 230. The limit for bringing it on a plane (at least in the US) is 100 WHr, so almost no laptops have a battery larger than that. At 80 WHr, 3 hours is 27W, and 8W is 10 hours. Also, I have never seen a 16V battery. I have only ever seen 10.8-11.4V batteries in laptops. I have heard rumors of 7.4V and 14.8V batteries being used, but have never seen one. 16V is not a multiple of anything between 3.6 and 3.8. And I highly doubt the laptop is drawing 77W under low load. With a few exceptions, most draw under 40 at most, and less normally.

power_now: 15105000
voltage_now: 15000000
energy_now: 15000000

Didnt find the other one you asked for

Your battery is at 15V at the moment. This suggests a battery with a nominal voltage of 14.8V (4 cells in series), slightly more than half charged. You are drawing 15.105W, and your battery has 15WHr of energy left. From this, we can conclude that you've had it on battery for about an hour (assuming no charging was done), and have about an hour of life left for two hours total. Your battery is about 2 Ah or 30 WHr.

However, those values given look too "clean" to be correct. I suggest looking at the physical battery to see if they make sense.


btw I use Arch

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#5 2020-10-15 15:18:37

ewaller
Administrator
From: Pasadena, CA
Registered: 2009-07-13
Posts: 17,463

Re: Bad battery performance

VDmvKcW9JamBSir5fNfehqpG wrote:

The principle is right, but your details are wrong, 5Ah at 16V is 80 WHr, not 230.

Doh!  I have no idea how I screwed up that product.  Thanks for the catch.

The limit for bringing it on a plane (at least in the US) is 100 WHr, so almost no laptops have a battery larger than that.

I did not know that.   Good data point

At 80 WHr, 3 hours is 27W, and 8W is 10 hours. Also, I have never seen a 16V battery. I have only ever seen 10.8-11.4V batteries in laptops. I have heard rumors of 7.4V and 14.8V batteries being used, but have never seen one. 16V is not a multiple of anything between 3.6 and 3.8.

True about the battery voltage being product of the number of cells and the cell voltage.  I don't know about batteries in practical use -- I was really just taking a swag.  This laptop battery is rated at 14.8V, and the present voltage (full charged, external supply connected) is 16.8V.  When I disconnect power, it hangs around 16.5.

And I highly doubt the laptop is drawing 77W under low load. With a few exceptions, most draw under 40 at most, and less normally.

I guess this is the unknown smile

TyphooNN wrote:

power_now: 15105000
voltage_now: 15000000
energy_now: 15000000

Your battery is at 15V at the moment. This suggests a battery with a nominal voltage of 14.8V (4 cells in series), slightly more than half charged. You are drawing 15.105W, and your battery has 15WHr of energy left. From this, we can conclude that you've had it on battery for about an hour (assuming no charging was done), and have about an hour of life left for two hours total. Your battery is about 2 Ah or 30 WHr.

However, those values given look too "clean" to be correct. I suggest looking at the physical battery to see if they make sense.

What puzzled me was the "energy_now" value.   Energy should either be in Joules or W-h (or variations on the theme V-A-hour, kJ, mWh, ...)  You took that to be 15Wh, and you may be correct, but, as you point out, the voltage now and energy now are just a little too perfect.  And, I am skeptical as they are the same value.    The other thing we do not know is, what is the "energy-now" value at which the battery controller will shut things down?  Zero?   Does the value represent the remaining usable energy? or does it represent the energy stored in the cells?

TL;DR:  If we fix my basic math error, and take your nominal value of 40W,  we are back at 2 hours.    As you point out, 10h would require 8W -- not a chance with multicore processor, GPU, backlight, Wifi, and perhaps a spinning disk.


Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Sometimes it is the people no one can imagine anything of who do the things no one can imagine. -- Alan Turing
---
How to Ask Questions the Smart Way

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#6 2020-10-16 13:37:37

TyphooNN
Member
Registered: 2020-07-14
Posts: 4

Re: Bad battery performance

VDmvKcW9JamBSir5fNfehqpG wrote:
ewaller wrote:

I don't place much faith in Powertop.  It depends on the pseudo file system /sys/class/power_supply/BAT0.  I prefer to look at the content of those "files" directly.  But, those values are dependent on what the smart battery itself reports.

I don't believe your system is running on 8W.    I would believe 50 to 75W depending on back light brightness, CPU load, Disk drive type, GPU activity, and attached USB devices.

And ~3 hr of battery operation is not terribly unreasonable.
How big is the battery?  Is that expressed in Amp-hours, or Watt-hours.  If Amp-hours, what is the battery voltage?
A typical battery is about 5 Ah at 16V, or 230 Wh.  Three hours of life would be 77 W.

While discharging, look around in /sys/class/power_supply/.  Your battery will be called something like BAT0.  There will be a directory for it containing "files" such as current_now, charge_full, charge_now, and voltage_now.
Post the contents of those (noting what files they came from).

The principle is right, but your details are wrong, 5Ah at 16V is 80 WHr, not 230. The limit for bringing it on a plane (at least in the US) is 100 WHr, so almost no laptops have a battery larger than that. At 80 WHr, 3 hours is 27W, and 8W is 10 hours. Also, I have never seen a 16V battery. I have only ever seen 10.8-11.4V batteries in laptops. I have heard rumors of 7.4V and 14.8V batteries being used, but have never seen one. 16V is not a multiple of anything between 3.6 and 3.8. And I highly doubt the laptop is drawing 77W under low load. With a few exceptions, most draw under 40 at most, and less normally.

power_now: 15105000
voltage_now: 15000000
energy_now: 15000000

Didnt find the other one you asked for

Your battery is at 15V at the moment. This suggests a battery with a nominal voltage of 14.8V (4 cells in series), slightly more than half charged. You are drawing 15.105W, and your battery has 15WHr of energy left. From this, we can conclude that you've had it on battery for about an hour (assuming no charging was done), and have about an hour of life left for two hours total. Your battery is about 2 Ah or 30 WHr.

However, those values given look too "clean" to be correct. I suggest looking at the physical battery to see if they make sense.

I dont understand the problem here, and why should I check my physical battery?
I just bought new battery from aliexpress.

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#7 2020-10-16 15:12:07

VDmvKcW9JamBSir5fNfehqpG
Member
From: Earth
Registered: 2019-12-30
Posts: 36

Re: Bad battery performance

When your battery life is too short, one or both of these things is true:
1. Your computer's average power consumption is too high
2. Your battery's energy storage capacity is too low

I suggested checking your physical battery, specifically the electrical ratings on it, so that you know for sure what the voltage and capacity are supposed to be. This will let you know if there is something wrong with the numbers that you are seeing, either a bug in your drivers or your battery misreporting the numbers, as well as tell you how much energy you should expect to be able to store. I'd also suggest checking the reviews of your specific battery and the seller you bought from, as well as doing a capacity test if you have the means to, because Aliexpress has been known to sell fake batteries.

Whether or not you are able to find out how much energy you have to work with, your focus should be on decreasing your laptop's power consumption. Your powertop screenshot shows 56.1% CPU use. If it's always that high, that might be a good place to start.


btw I use Arch

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