Battery or recharge circuit problem - C860

[Aussie]

My Sharp Zaurus C860 arrived during the week, and pdaXrom was installed as per:   http://www.pdaxrom.org/index.php?showid=2&menuid=1

When I rebooted, the Linux operating system was eye candy at its best, and after a bit of a hack around, the system was shutdown by the command "halt".  

A few hours later, I press the ON button and ... nothing but a black screen :-((  

After reading all web sites and forums, all that I can do is get into a service menu by holding down keys D+M whilst plugging in the AC/DC charger.  

Running through all the hardware checks on this service menu, everything seems to work OK except the battery status is LOW.  Multimeter confirms that the battery is now 2.4V, and well below its normal fully charged voltage of 3.7V. However, placing the Zaurus/battery on the charger for several hours just doesn't recharge the battery !  

Is the battery or the recharging circuit in the Zaurus faulty, or is there something else that I should be doing ?

Help appreciated.  

-- Aussie

[lardman]

I'm not sure the system should be halted.

What happens if you remove the battery for a bit (10sec - make sure no external power is supplied too) then try starting up (button on the back) - you may have to hold it for a little while. Hopefully you'll boot again.

It's possible that the charging is controlled by the Z hardware (which was powered down when you halted - at a guess). Try charging it once it's come back to life.


Si

[Aussie]

What happens if you remove the battery for a bit (10sec - make sure no external power is supplied too) then try starting up (button on the back) - you may have to hold it for a little while.

Still dead as a dodo - black screen. The battery is drained down to 2.4V and the Zaurus won't boot up at this low voltage. All I can get is the service menu using the D+M+plug in AC/DC charger sequence.  And the battery will not recharge at all whilst in the Zaurus.

I was thinking of trying:
1) charging the battery outside the Zaurus directly from the charger;  
2) rigging up an alternative power supply directly to the Zaurus to see if it powers up normally (I know I have to be careful to use the exact specs); and/or  
3) borrowing another battery - this is no doubt the safest, but will take a few days.

? comments.

Aussie

[Miami_Bob]

Try pulling the battery for an extended period of time. Several hours. There have been a couple of reports that I recall on hard to start C860s after full "halts". At least one person reported charging the battery externally.

You might want to try booting with D+M, go to page 2, line 10, Charge, Enter & "left arrow" charging ON (use the "<- BS" key to get back out to the menu).

Be very carefull about running "hardware checks" from the D+M menus! Some (like AGING in the Extra Menu) have been reported to hard brick the Z.

Luck!

[Aussie]

You might want to try booting with D+M, go to page 2, line 10, Charge, Enter & "left arrow" charging ON (use the "<- BS" key to get back out to the menu).

Thanks - I did this overnight, but the battery still didn't recharge :-((

I have 2 battery chargers - both working normally with the multimeter showing outputs of 5v (positive inside, negative outside).

I also did a NAND flash restore, which didn't help.  

What is the "Batt Voltage Adjust"  (service menu, page 2, line 6) ?

Aussie

[Miami_Bob]

What is the "Batt Voltage Adjust"  (service menu, page 2, line 6) ?

Aussie

Try -

https://www.oesf.org/forums/inde...=4068&hl=adjust

http://externe.net/zaurus/forum/viewtopic.php?t=620

[Aussie]

Thanks Miami Bob.  Those links were helpful, but they still do not spell out a solution.  What I think is happening is ...

There is a battery voltage level kept in memory which is the voltage up to which the charger will charge the Zaurus battery.  This should be about 4.2V (the maximum voltage up to which the battery is charged).  

It seems that certain actions can erase this voltage from memory, which prevents the battery from charging through the Zaurus circuitry.  

The way to rewrite a voltage to memory is through the service menu, battery voltage adjustment - but this will only flash the memory with the voltage that the battery has at that time.  If the battery is fully charged, then the memory will be flashed with a voltage that will allow the Zaurus to boot up and run, and the charger will thereafter recharge the battery back up to this level. But if the battery has drained, then any reflashing will only allow recharging back up to this lower level ... In my case, my battery drained down to 2.4v, and so I can only reflash the memory with 2.4v, which is insufficient to boot my Zaurus.

Solution (I hope):

1) Get a new fully charged battery, and do a battery voltage adjustment/reflashing which would then allow recharging to this level.

2) Somehow recharge your existing battery outside the Zaurus (which will require a little creative ingenuity).  Then replace the externally recharged battery into the Zaurus and do a battery voltage adjustment.  

3) As a variation on 2), you can put your battery in the fridge to gain a small recharge.  Then replace it into the Zaurus, do a battery voltage adjustment, and then recharge the battery in the Zaurus to this new higher level. Repeat until the battery voltage adjustment is 4.2v.  

I will give 3) a try first, and report back.

Aussie

[Aussie]

Success !!! .... one Z C860 unbricked :-)))

Everything in my previous post seems true, and is explained in more detail below ...  

1) THE BATTERY & CHARGER CIRCUITRY:
The Zaurus has a system to protect its circuitry, which can only be powered directly from the battery (with the excpetion of the service menu).  The AC/DC charger charges the battery, and the battery powers the Zaurus circuitry.

There is a voltage level flashed in memory - this should be 4.2v = a fully charged battery. When the battery is fully charged (=4.2v) the AC/DC charger cannot send current through to the battery (preventing overcharging and damage to the circuitry). When the battery voltage drains below this, the AC/DC charger can then recharge the battery, and the LED light will be on continuously. When the battery has charged, then no further current can flow through to the battery, and the LED blinks intermittently.

2) THE PROBLEM:
The problem that arises is that the voltage level which is flashed in memory becomes erased - I have not explored the reasons for this, but it happens. With this erased, then current cannot flow from the charger to the battery, and the battery drains such that the Zaurus won't boot (= bricked). Put in a new battery, and the Zaurus works again for a few hours until this new battery has drained.

3) THE FIX:
Now, there is only one way to flash a new voltage level to memory - via the service menu, which is accessed by holding down the D+M keys whilst pluging in the AC/DC charger. Here on page 2, option 6, is the Battery Voltage Adjustment. The Main Bat AD: is the present voltage of the battery.  Flash data: - -  is the voltage level stored in the Zaurus memory.  You can flash the present voltage of the battery into memory by pressing the [Home] or key.  But this will only flash the present battery voltage level, and there is no way of changing this. And if the present battery voltage has drained, then there is not much use in flashing a low voltage into memory - you need to flash a working voltage (preferably 4.2v).

What I did was simply charge my battery outside the my Zaurus by just connecting a wire from the positive centre of the charger to the positive battery terminal, and from the negative outside of the charger to the negative battery terminal. I then monitored the battery voltage level as it charged using a multimeter, and stopped charging once the battery voltage was 4.2v (it charged from 2.4v to 4.2v in about 2 hours).

Then, the fully charged battery was replaced in the Zaurus, and this voltage was then flashed to the memory.  

Success ... Zaurus unbricked, and all working perfectly.

I hope this HOW TO can be useful to others with the same problem of the battery not charging, and who suspect that the battery is a dud or the Zaurus circuitry is faulty.  

Best wishes from Down Under.

-- Aussie

[Omicron]

Now added to HOW-To Section:

URL:

http://www.zaurususergroup.com/modules.php...%20not%20charge


Thanks Aussie !!!

[cgrieves]

Interesting post, unfortunately I think there is still an inherent problem with some Cx60 and this kind of confirms it for me.

My C860 has the charging problem and when I first realised it a few weeks ago I checked the voltage values in the service menu. They were all blank (i.e. ___) so I flashed them using a fully charged large battery, but the problem remained up to a point. The battery would charge up to around 30-40% but no more. I also came to the conclusion that the charger charges the battery while the battery powers the Zaurus, because the battery would charge higher if I removed all the peripherals, memory cards and powereed down the LCD. It would still only charge very slowly though. However I found it would not charge for more than a few minutes if I powered down the Zaurus. So it would seem that the voltage drop due to having the Zaurus running pulls the battery voltage down far enough to allow it to charge to an extent.

This lead me to believe that the Cx60 problem is not so much a charging problem as a voltage measurement problem- and after reading your post I think I have confirmed this. I have an external battery charger and three fully charged batteries. No matter what battery I use, the service menu only registers a maximum MAIN BAT AD: 213 (2.7V) even thought the batteries are fully charged. If I flash the adjustment with this battery I get:

MAIN BAT AD:   213 (2.7V)

Flash Data:       213
Delta:              +439

Adjust AD:       213 -> 652
              :        (4.2V)

To test this I used a small battery for a day or so and let it run down to nearly discharged, then charged it in the Zaurus for about three hours (using the powered-on but screen-off technique). I then plugged my CF wifi card in, VNCd to the Zaurus from my PC over the wireless network to keep it active and then tested how long it lasted. The battery charge as detected by the Zaurus started at 40%, then almost immediately dropped to 10%, but then the Zaurus stayed up for just under 50 minutes with the wifi card active, indicative of a reasonably well charged battery. During those 50 minutes the indicator slowly counted down to 3% when the Z powered off.

This implies to me that the Zaurus had trickle charged the battery to a fairly high level, however the voltage detection circuitry could not measure that voltage correctly, so it thought I had 10% power. In fact the battery was reasonably charged and gave a decent lifespan with a wifi card active.

The only thing I haven't done yet is actually measure the voltage of my batteries. Maybe all three are dead and really only giving 2.7 volts but it seems unlikely.

I may rig up a 4.2 volt power supply, feed it to the battery terminals in the Zaurus and flash the voltage adjustment data and see what happens. Maybe it will revive my Zaurus.

[lardman]

1) THE BATTERY & CHARGER CIRCUITRY:
The Zaurus has a system to protect its circuitry, which can only be powered directly from the battery (with the excpetion of the service menu). The AC/DC charger charges the battery, and the battery powers the Zaurus circuitry.

Hmm, I'm pretty sure you can run the C machines without a battery in them - just plugged into the external supply (though I'll check again).

In any case an interesting thread.


Si

[Aussie]

I'm pretty sure you can run the C machines without a battery in them - just plugged into the external supply

No, I just tried to run my C860 from the external supply (AC/DC charger) without the battery in, but it wouldn't run.  Put the battery back in, and it runs.

The only thing that I can run without the battery is the service menu.

Cheers from down under,

-- Aussie

[cgrieves]

Aussie, can you post what battery check values you get in the service menu when using a fully charged battery? (AD, Flash data, delta, adjust AD etc etc). Many thanks.

[Aussie]

Will do, but it will be in a few days (next weekend) when I have a multimeter again.  

What I will do is:

1) charge the battery outside the Zaurus - the multimeter shows that the battery charges to 4.2v quite quickly with my 5.1v, 2.5amp AC>DC charger. Then put the battery in the Z and check the service menu battery voltage adjust readings.

2) run the battery down, and recharge it in the Z until it is fully recharged. Then check the multimeter voltage of this fully charged battery, and the service menu battery voltage adjust readings.

Perhaps others might like to do the above also - all you need is a simple multimeter with positive/negative probes.

-- Aussie

[Miami_Bob]

Hmm, I'm pretty sure you can run the C machines without a battery in them - just plugged into the external supply (though I'll check again).

In any case an interesting thread.


Si

My C860 shows same behavior. No battery, no "normal" power on even using AC. Replace battery, powers on as usual.

NOT good planning on Sharp's part, IMHO without some way to go arround it.

VERY good thread, Aussie. But, are you puting the battery under a load to measure the voltage? I know that AA cells show 1.5v with no load when their voltage under load (like in an HP200LX) is significantly lower. Might be a factor.