"Franc Zabkar"
** Impossible is the word.
** With devices like mobile phones or lap tops there is often a micro
dedicated to monitoring the internal battery - the time duration and the
rates of charge or usage are constantly measured, the data is processed and
a **model** of the battery's likely condition held in memory and also
displayed as a "fuel gauge".
That's the prevailing technology for expensive lithium laptop
batteries, but I don't believe my mobile phone battery works that way.
Sometimes the calculated **model** and the battery get right out of whack
and the micro has to be reset while the battery is fully cycled -
likewise if the battery becomes defective or dies of old age the model will
be wrong.
If your model were to apply to my phone, then why would it display a
50% battery meter while warning that the battery was low?
With an old battery, I have observed the battery meter drop to about
25% over a couple of days and then mysteriously increase. No calls
were made or received during this time.
I have two identical phones with identical, genuine Ericsson NiMH
batteries. If I swap batteries between phones, one fully charged, the
other at about 25%, then the phones correctly assess the state of
charge of the replacement batteries ... almost. The fully charged
battery from phone A shows only about 90% in phone B.
My conclusions are that there is no intelligent IC within the battery
pack, otherwise the SOC info would be communicated to the new phone.
Secondly, the phone itself senses the SOC in some way, probably by
measuring the terminal voltage at a certain discharge rate. That's why
the battery meter is often updated during a call, especially when the
SOC is low.
One other observation about my phone is that it will refuse to charge
a battery pack that it considers to be dead flat. To get around this,
I trickle charge the pack using a DC supply and series resistor until
the voltage is at a reasonable level. I then install it in the phone
and allow the phone to complete the process.
- Franc Zabkar