I use Linux, but am wondering if Windows has the same issue.

My software shows my Logitech mouse battery as showing 55% for both a alkaline battery, a rechargeable LiMh, and another AA battery.

Only the LiMh is fully charged of the batteries, so there is no way they are all 55%.

Are others seeing something similar ?

Curious.

Thanks,
Andy

AK wrote:
> I use Linux, but am wondering if Windows has the same issue.
>
> My software shows my Logitech mouse battery as showing 55% for both a alkaline battery, a rechargeable LiMh, and another AA battery.
>
> Only the LiMh is fully charged of the batteries, so there is no way they are all 55%.
>
> Are others seeing something similar ?
>
> Curious.
>
> Thanks,
> Andy

Laptops use a coulomb counter. Because they in effect, measure "fuel",
the percentage figure is relatively trustworthy.

But other devices use a simple voltage measurement, then
consult an open circuit voltage versus time table, to
guess at how much of the battery is left. This is
fraught with error.

In your case, the Logitech does not know the cell chemistry.
Consequently, it cannot "pop the correct table" into the
math. It has probably assumed alkaline chemistry for all
three readings, causing a fully charged LiMh to read
lower than it should.

The table is not linear. Most of the discharge curve,
the battery may only change a little bit in voltage.
Near the end of the discharge curve, there is a
much larger change in voltage, so maybe it changes 0.5V
between 5% charge and 4% charge. That's riding down the
knee at the end. You could compute the inverse of the
table used, then correct for the chemistry and apply
a different table. But an even easier way, would be
if the Logitech software stopped being so clever ("55%"),
and the voltage measurement it's doing, was just
printed on the screen instead ("1.354 volts"). Then, you
could take the discharge curve yourself, and work out percent
remaining.

Paul

On Sunday, July 25, 2021 at 10:08:36 PM UTC-5, Paul wrote:
> AK wrote:
> > I use Linux, but am wondering if Windows has the same issue.
> >
> > My software shows my Logitech mouse battery as showing 55% for both a alkaline battery, a rechargeable LiMh, and another AA battery.
> >
> > Only the LiMh is fully charged of the batteries, so there is no way they are all 55%.
> >
> > Are others seeing something similar ?
> >
> > Curious.
> >
> > Thanks,
> > Andy
> Laptops use a coulomb counter. Because they in effect, measure "fuel",
> the percentage figure is relatively trustworthy.
>
> But other devices use a simple voltage measurement, then
> consult an open circuit voltage versus time table, to
> guess at how much of the battery is left. This is
> fraught with error.
>
> In your case, the Logitech does not know the cell chemistry.
> Consequently, it cannot "pop the correct table" into the
> math. It has probably assumed alkaline chemistry for all
> three readings, causing a fully charged LiMh to read
> lower than it should.
>
> The table is not linear. Most of the discharge curve,
> the battery may only change a little bit in voltage.
> Near the end of the discharge curve, there is a
> much larger change in voltage, so maybe it changes 0.5V
> between 5% charge and 4% charge. That's riding down the
> knee at the end. You could compute the inverse of the
> table used, then correct for the chemistry and apply
> a different table. But an even easier way, would be
> if the Logitech software stopped being so clever ("55%"),
> and the voltage measurement it's doing, was just
> printed on the screen instead ("1.354 volts"). Then, you
> could take the discharge curve yourself, and work out percent
> remaining.
>
> Paul
Thanks for the info.