Add me to the list of people with low Pre3 battery health. Mine says 49% and I haven't been able to get it to change.
The battery has been sitting around for several years, obtained during the fall of Palm. Used for only a few cycles. It was stored in a dry place with what should have been around 70% charge. My in-use Pre3 battery is getting close to 80% health so I thought I'd better check up on this reserve battery. Shocked to see the health had deteriorated with NO USE!
Since then, I've tried charging and discharging but with no success in recovering the health. What is pissing me off is that something is preventing the battery from fully charging. I don't know if it's the in-battery chip or the Pre3 firmware.
I actually wrote Li-ion battery charging software for a major semi company many years ago. The info in the Maxim data sheet is consistent with my knowledge. The algorithm for determining the true health of a battery is basically the same one we used. The battery must be fully discharged (Voltage Active Empty point) and then coulombs going into the battery are counted while it is charging until the fully charged voltage is reached. This is typically around 4.2 V. On my Pre3 with a normal battery, Dr. Battery shows battery current flipping form charge to discharge at 4.17V.
But the charger for the Pre3 is not using voltage to terminate charging. It appears to be using the messed up health reading. Since my battery has "only" 49% health left, the maximum mAh it can hold is supposedly 607 mAh. So battery is allowed to charge up to 607 mAh + 100 mAh allowance. And then it stops charging. But the battery voltage is only 3.85V!! WTF? It's not even close to full. And if the battery never reaches the full charge voltage, the chip can't recalibrate the battery's health.
Got to see if there's a way around this bad programming.