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carlito

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28 Jul 2006
Hi guys, gals, and small furry creatures from Alpha Centauri,

After a lot of experimenting, and a lot of reading here on OESF, I finally tracked down the source of my mysterious battery problems with my Zaurus SLC-860. I'd like to describe in detail the problem I had and its solution, in case anyone else may have a similar problem.

Summary:

The basic problem was a faulty power cable preventing enough current from reaching the battery to fully charge it, but providing enough current to light the charging LED and barely, weakly charge the battery. This took a long time to diagnose due to the odd symptoms.

History:

Zaurus SLC-860 and EA-BL08 1700 mAH battery are almost 3 years old.

Original Zaurus AC adapter silently died after about 1 year. I occasionally used external commercial battery packs with the Zaurus. I never, ever connected reverse polarity or over-voltage to the Zaurus, so I was pretty sure I didn't destroy the Zaurus charging circuit.

I bought a replacement adapter with a very thin power cable, rated at 5V 1000 mA and (apparently) regulated. Measuring output with a voltmeter gave 5.2v, within acceptable tolerance.

The replacement adapter worked fine for many months, then came... THE PROBLEMS.

Problems and symptoms:

1. Charging light comes on when A/C adapter plugged in, but battery doesn't charge, even overnight.
2. Zaurus turns itself after a few minutes off due to insufficient power, even while connected to A/C adapter.
3. Battery life when not connected to A/C adapter is around 10 minutes.
4. Measuring charger voltage gives 5.2 volts, the expected value.
5. Charging only works with Zaurus completely turned off. Afterwards, still only about 10 minutes of use.
6. Charging only continues for about 15 minutes, then stops (the charging LED turns off), even if battery is not full. Unplugging and replugging charger leads to another 15 minutes of charging.
6. Measuring charge voltage at battery terminals of Zaurus during charging (having pulled out the battery during charging) gives 4.2 volts, the expected value.
7. Using the "D+M charging trick" described elsewhere on these forums didn't charge the battery; it drained it. Note: the D+M charging trick is to go into the D+M service menu, then go to screen 2 and select "Batt Voltage Adjust", then plug in the AC adapter and leave the Zaurus sitting on that "Battery Voltage Adjust" screen (where it shows "Main Bat AD" and "Flash Data" and "Set Flash"). According to another article on these forums, this should charge the battery even above the set flash level.
8. The adapter never got really hot when charging.
9. The maximum battery voltage, measured with a multimeter, was ~3.74 volts after charging with Zaurus turned off and repeatedly plugging/unplugging the charger for several 15-minute charging sessions (see symptom 6). This was below expected; according to other posts, the maximum voltage should be 4.2 volts for a fully-charged battery (though the battery is rated at 3.7 volts).
10. The maximum "flash level" of the battery after charging (shown in D+M menu "Low Battery" or "Batt Voltage Adjust" menus) was 198. This was below expected; it should be above 200 (one report listed 217 as a maximum obtained value).

The pitiful battery life made it effectively impossible to use my Zaurus. After suffering what seemed like ages of horrible chills, aches, and fever - also known as Zaurus Withdrawal Syndrome - I set about in earnest to understand and solve the problem, with the following results.

The cause:

The thin power cable apparently became partly broken, enough to prevent the Zaurus from ever receiving enough charging current. Still, a multimeter showed 5.2V coming from the charger, so I didn't originally suspect the cable. But, eventually I excluded other possible causes and became convinced the cable was to blame, so I spliced the cable for the new adapter together with the old cable and plug from my old broken adapter, and - after verifying multiple times that I did not accidentally reverse the polarity - connected the newly spliced adapter/cable to the Zaurus.

Now the Zaurus is charging normally again.

Continued in next post...
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