Battery Charge Full greater than Charge Full Design

AdmnUnpwnd · 2017-01-03 06:57:16

Hello,

I just got a brand new Eluktronics P670RP6 (Clevo rebranded) laptop and I noticed that the battery charge values are greater than the full values by design.

Here is what I've ran and their respective outputs:

cat /sys/class/power_supply/BAT0/charge_full

cat /sys/class/power_supply/BAT0/charge_full_design

cat /sys/class/power_supply/BAT0/charge_now

At 100% : 4690000
At 96%: 4492000

acpi -bi

Battery 0: Discharging, 95%, 02:31:05 remaining
Battery 0: design capacity 4000 mAh, last full capacity 4690 mAh = 100%

Can someone please explain to me why the charge_full is greater than charge_full_design and why my battery's full capacity at 100% is 4690 mAh while the design capacity is 4000 mAh? Would this be a hardware issue?

Thank you.

EDIT:

If it helps here are the voltage values:

cat /sys/class/power_supply/BAT0/voltage_min_design

14800000

cat /sys/class/power_supply/BAT0/voltage_now

At 100%: 16358000
At 61%: 14890000

Last edited by AdmnUnpwnd (2017-01-03 07:13:18)

R00KIE · 2017-01-03 10:37:37

Charge full design is a value that is preprogrammed to the charge gauge circuit in the battery and it takes into account the nominal capacity of the battery. Charge full is the value measured by the charge gauge circuit after a full discharge and charge and it can be larger, not all cells are exactly the same, some might have a little less capacity than nominal, some might have more, and that value will decrease with use and aging as the cells will hold less charge.

In your case the discrepancy is very large so I would assume the manufacturer of the battery screwed up on that one and programmed the wrong value to the charge gauge circuit. I would probably dismiss that as a mistake but it could also be to make the battery seemingly last longer, if I'm not mistaken when at full charge the battery can hold not more than 85% of the nominal charge then it is considered at end of life, if you program a lower value it will seem to last longer if you take the values and do the math without knowing the history of the battery.

In any case that should not influence the operation of the battery or the machine, as long has the charge now value reflects the true state of charge the software you are running on your machine should do the right thing and take only the charge now and charge full values to show you the percentage of charge remaining.

AdmnUnpwnd · 2017-01-09 00:15:47

ROOKIE, thank you very much for the reply.

R00KIE wrote:

In any case that should not influence the operation of the battery or the machine, as long has the charge now value reflects the true state of charge the software you are running on your machine should do the right thing and take only the charge now and charge full values to show you the percentage of charge remaining.

How do I find out the true state of charge? I'm assuming the charge now is the percentage that I see that gets calculated by the software. Would using IBAM (Intelligent BAttery Monitor) help?

R00KIE · 2017-01-09 15:08:15

The true state of charge should the the ratio charge_now/charge_full. Multiply by 100 if you want a percentage. The only thing you cannot be very sure about is when the battery has reached end-of-life, which is typically when it cannot hold more than 85% of the design capacity, you would calculate it as charge_full/charge_full_design.

Regarding IBAM I can't comment, I don't use it myself and I haven't seen people discuss it here on the forums, it seems to be in [community] so it shouldn't be too hard for you to give it a try and see if it works for you.

AdmnUnpwnd · 2017-01-11 02:40:00

Thank you.

My true state of charge seems to be matching what ACPI reports. charge_full/charge_full_design however is greater than 1. I am getting 4512000/4000000 = 1.128. As you said before this seems to be an issue due to the incorrect value being programmed in for the charge gauge circuit, but this could pose a problem when I would have to check for the battery's end-of-life. Do you know of any way to remedy this or is it just not possible?

R00KIE · 2017-01-11 13:45:28

It should be possible to reprogram the correct value but you would need more than that, a lot more. If I were you I would just keep note of the charge_full value you have now. That end-of-life value of 85% is a convention, it had to be defined when a battery reached its end-of-life but it doesn't mean you can't continue to use, you will have less on battery time but it will still work.

I reckon that you will most probably think about replacing it only when it holds less that 50% charge or it stops working completely so don't lose sleep over that. You could ask about that problem to the people that sold you the laptop but I suspect they will not bother fixing it. Normal state of charge is reported properly and end-of-life is not that much of a big deal, you replace the battery when you feel it is not holding enough charge for your needs.

Trilby · 2017-01-11 14:05:12

FWIW, My current laptop battery is at 56% (full/full_design). I still quite happily use it. But this is not a laptop I take out and about without the adapter. It is fine unplugged for a while, a couple hours here and there is no problem. I've not tested it beyond that and ACPI estimated time remaining while running on battery seems to suggest ~2hrs from full to dead.

But I also drive a vehicle that is many years past any manufacturer warantee. I'm sure they'd prefer I bought a new vehicle from them ... but this one works just fine

AdmnUnpwnd · 2017-01-15 05:19:34

ROOKIE, Trilby, thank you very much for the reply.

There seems to be some other issue as charge_full is now reporting 4788000 which is higher than what I originally posted. I will not worry too much about it as there seems to be nothing much I can do, and even though the value of charge_full has changed the true state of charge (charge_now/charge_full) is still matching what ACPI reports.

Thank you again.

Arch Linux

#1 2017-01-03 06:57:16

Battery Charge Full greater than Charge Full Design

#2 2017-01-03 10:37:37

Re: Battery Charge Full greater than Charge Full Design

#3 2017-01-09 00:15:47

Re: Battery Charge Full greater than Charge Full Design

#4 2017-01-09 15:08:15

Re: Battery Charge Full greater than Charge Full Design

#5 2017-01-11 02:40:00

Re: Battery Charge Full greater than Charge Full Design

#6 2017-01-11 13:45:28

Re: Battery Charge Full greater than Charge Full Design

#7 2017-01-11 14:05:12

Re: Battery Charge Full greater than Charge Full Design

#8 2017-01-15 05:19:34

Re: Battery Charge Full greater than Charge Full Design

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