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#21 Lubo

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Posted 16 June 2011 - 02:39 AM

Ok, I get my ordered IC chip,
and successfully replaced it :)

i am talking about that small one, marked in red rectangle, replaced it with this:
http://bg.farnell.co...4427?Ntt=BQ2057


engineer who do the soldering said, that it is usual
when reversing polarity, to burn transistor together with this IC.

Now tablet works, charging somehow works, unplugged at 50 % and last more than 2 hours.
but red light is on all the time, even if tablet is powered off and android is shutdown.
this red light turns off only when battery is fully discharged.

then powering tablet and no date and time...

so, replacing this IC is not enough, but a bit better than before.
no more over heating

#22 0rion

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Posted 20 June 2011 - 10:44 AM

Some interesting developments - it's been quite awhile since my tablet developed this issue, I thought I'd try a couple things based on what others have tried...

Started by getting a regulated AC Adapter for it, for other Canucks it is this adapter from The Source with with the type A tip - left it a few days and nothing changed, still at 1% charge.

I've been reading that when a Li-ion battery goes below a certain voltage it can be tough to get it to charge up again. My theory is that I left it on (with screen off) too long and the Phone.apk drained it. Going with this theory, some have managed to revive their batteries by sticking them in the freezer for a few days. Since I still don't want to take it apart to remove the cells, I put the whole thing in a ziplock bag and into the icebox. Yup, I had a C8-sicle. 48 hrs in the box, and 24 hrs out (wrapped in newspaper to absorb any moisture) then another 24 hrs on the regulated charger - 12 with power switch off and 12 with it on.

Drum roll....

Nothing. Still at 1%.

So I just kinda gave up and kept it by my bed with the power on and screen off, plugged in and ready to use.

Three days later I went to use it and saw the battery level at 3%! Encouraged and excited I ran the battery calibration tool and unplugged it and was amazed to see the percentages climbing as it calibrated itself! It went as high as 20% before its decent back down, and gave me about 25 minutes of sweet battery life.

I thought that this may have revived the battery but its back on the charger and holding at 1% again. Sigh.

I'm not sure if that was a one-off - it kinda reminds me of the movie Awakenings!




#23 Aimevous

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Posted 20 June 2011 - 11:02 AM

For mine, it just takes about 16 hours to do a full charge.

I'm not sure why its taking so long but at least it does get to 100% =/

#24 JcNeji

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Posted 20 June 2011 - 02:09 PM

I have the same problem as you 0rion, and its kinda starting to anger me a little bit :p

It worked fine for weeks (with the provided charger) then all of a sudden it took FOREVER to charge (like 20 hours to get from 1% to 100%) and after that it just stuck on 1%, cant unplug it without it turning off immediatly :s

#25 ronnie2

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Posted 20 June 2011 - 06:40 PM

I don,t know if my problem is the same. Had my c8 for about 2 months now. What happens to me is when i have a usb flash drive connected and remove it without shutting it down first or sometimes when it connected to my pc. Afterwards it will only power on when connected to charger and dies as soon as i unplugged it. If I then connect it to my pc wile running on the charger,and then safely remove the device it would charge again to 100%. Maybe there is a short circuit somwhere when not disconnected safely.
Ronnie

#26 JcNeji

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Posted 21 June 2011 - 04:27 AM

Thx for you post ronnie, but I tried this a couple times just now and it doenst help me sadly :(

#27 0rion

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Posted 23 June 2011 - 02:48 PM

Well, the battery seems to be responding better - my previous experience wasn't just a 'one-off'. I can unplug the power cord and will occasionally get 20 - 30 minutes of life. I can't rely on the battery meter though, it will bounce around from 2% up to 10% and back down.

Nice to have a bit of freedom to roam around the house with it now and then!

#28 JcNeji

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Posted 23 June 2011 - 03:12 PM

I THINK (and really think cus it just happened) that it is somehwat fixed:

My friend also has a c8 so i borrowed it and desoldered both batteries to see if my problem was with the battery or with the device itself

Turns out that my battery charged just fine in his c8, but when i put his battery in mine (which was 80% full) i could not get mine to boot and with AC power it once again said 1%.

I gave up and thought the problem was solely with my tablet, so i desoldered the batteries again and switched them, but THEN my tablet booted up fine with my own battery and without AC power and it showed 50%, but as soon as i connected it to the charger (tried multiple chargers) it started to drain rapidly and as soon as I disconnected the charger the batterymeter began to rise again.

So now im charging it with the power completely off (including the switch) to see where that leads me.

Ill update with my progress.

#29 eatatjoes

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Posted 26 June 2011 - 03:45 PM

Hi to all unhappy pad users,
I don't have any problems with my battery (yet, hope it never occurs!), my Dropad A8 runs for exactly 7(!) hours with screen, wifi, "phone" and battery-app all on.
I followed this thread (and some on DX) about battery and charging problems, to see, if I can help. So here are my thoughts so far, and hopefully a solution for that. It's a very long story, but if I can help only one user to get his pad back to work, it was worth reading it.
This should work on all pads that have a power supply with ~9V (or more than 5V), with batteries charged in series. If your pad is charged via 5V it might be, the cells in the pack are connected in parallel, I don't know about that. But the theory behind it is the same for all lithium-packs, and will explain very short lasting batteries:

Disclaimer: I'm not responsible for any damage on "warranty" or the pads, that occurs from following this discription. It is only an idea, to try to solve your problems.
Handling lithium-cells can be dangerous, if you don't know how to do it, don't do it!
Lithium-cell contain a huge amount of energy. When shorted, very high current will flow. So use a good multimeter with working protection, no chin. crap :angry:


I opened my pad, to help marcoslongo1 with his problem (identify a fried bug on the board) and so I had to take out the battery (but I did not open my pack!).
As written before, on the batteries back (glued to the display-back) is written "3,7V 1500mAh" on each cell. Since the voltage at the connection to the board and in all battery-apps is between 8,25V (right after fully charged) and 6,3V (auto shut-off) it is clear, that in the Dropad the cells are connected in series.

As I know about it (I use lithium cells in many flashlights and some r/c-applications), it is difficult to charge lithium packs without "balancing" the cell's while charging. One user at DX (he has a blown cell) wrote, there is a small circuit board found inside the cell-pack. So the small circuit inside the pack has to be either:
a - a charging circuit, or
b - a balancing circuit, or
c - a discharge/overcharge protection
d - any combination of a to c

- A charging circuit (a) combined in the cell-pack would be unusual, never saw that before. The pad gets a feedback from the cells while charging, so it's ok to believe like most of us, the main charging circuit is on the main board.

- A balancing circuit is possible on lithium packs, to increase the usable capacity, but usually this circuit is used outside of the pack, only while charging. But who knows? Charging two cells in series without any balancing is a bad idea, so it should be there.

- A discharge/overcharge protection circuit is very common on lithium single cells and also inside packs. It's small enough to be inside the pack and protects the cells from beeing charged to more than 4,2V or discharged to less than ~2,6V. In some cheaper applications this is also used as a kind of "charger circuit", because it will cut off the source, if the voltage goes over 4,2V (this will damage the cell or it might blow up). The charger then only feeds the pack with a high voltage, but low current.

I think, "c" (maybe combined with "b"!) is the best guess.

And this might be the explanations to your problems:

1 - The "only charging to 1-3%" problem could be because the "discharge protection" of one cell kicked in (e.g. you let the pad run down and didn't switch it off after some time). The protection circuit now cuts off the drain from the weaker cell, and has to be "resetted". Usually this happens, when connecting the pack to the charger, but on some chargers this doesn't work (on "crappy" ones) and has to be done manually.
Experienced lithium-users avoid this, because the protection kicks in at ~2,5V, this is a very low voltage for a lithium-cell. If it happens very often, the cell will still get damaged. The protection is "the last straw" to save the cell before it runs completely dead!
So, maybe resetting it doesn't work in some of your pads! With one working and one "shut down" cell the pack may still deliver some little power to show the 1-3% charging, but will shut down in minutes.
A possible solution to this can be found with help of god (Google!), but I never had to do this on my cells. I can not give any advice about that.

2 - The "blown cell problem": the overcharge-protection circuit failed to shut off at 4,2V.
The board delivers current until voltage reaches 8,2-8,3V. If one cell is weaker, it will get more than 4,2V and cell-protection kicks in. If this doesn't happen on both cells within a very short time, one cell gets heavy overcharged and thus blows up.
To check this, I advise to measure the "charging-voltage" on each cell seperately, especially when charging for a longer time. If the cell voltage raises to more than 4,2V your cell will be damaged in minutes.

The second case (overcharged cell) might have happened to you too. The cell doesn't have to blow up, but gets damaged very fast. It can not be charged any more, maybe it holds 3V, and your pad will show "low batt". If this is the case you have to replace that cell! It is not possible, to solve this with any software!

In both cases you should be careful, damaged lithium cells/packs are no toys. They can catch fire if continuously charged or might blow up and damage the pad (not worth a try!)

@ Orion:
you tested your pack in another pad and it worked well, so it seems, that your problem is in the pad, not the pack. But if you still have your battery-pack outside the pad its easy to check it (voltages). Give it a try, maybe you'll find the explanation there. Might be, your pads charging circuit is not able to reset the protection, but your friend's pad is! Maybe one of your cells is bad (very low capacity), and the protection shuts it off, every time you run your batt down to 0%.
How long did your battery last, after you charged it with your friends pad? Mine lasts 7 hours (see 2nd line of my post), so if yours last much less after fully charged, it's not good anymore!


A possibility to find out, if protection circuit kicked in or battery is bad:

If you are familiar with lithium-batteries you should know, how to handle them (careful!!).
To all others the advice: read my disclaimer in the beginning. Lithium-cells are dangerous, they can catch fire if opened or treated wrong in any way. So be careful with the following (first google "reset protection liion", read everything you can find about it :blink: , then go on!):

After connecting the pad to the power supply for 1 or 2 hours disconnect it. Open the pad (you all know, "warranty" is a chinese joke! :angry: ) and measure the voltage that goes from the pack to the board. With a good battery it should be between 6V (after pad shut down) and 8,2V (fully charged). In your case I think it will be between 3-4V, maybe slightly higher, that means one cell (or maybe both?) doesn't work or is bad.
Now to check the protection: you'll have to carefully open the pack (in my pad the blue adhesive tape, not the "silver" housing of the cells!) to get access to the cell-connections to the protection-board. Measure the voltage of each cell. If one cell is between 3,0-4,1V (depends on the charge) and the other is down to ~2,5V it might be shut off. Now reconnect the power supply and repeat measuring, if the voltage to the cell stays at that low value, it could be a) the circuit is not resetted, or B) the circuit is fried. If the voltage with power supply goes up, but after disconnecting it the cell-voltage rapidly drops back down, then the protection is ok but your cell is bad. You might be able to replace it (if you find them on www.)
If you're sure that the protection stays at "off", you can try to reset it (Google it). If the cell is dead this doesn't work, don't even try it!

I have to say, I never had to do this for my batteries before, it's only what I know about it. Google "reset protection liion" and you'll find explanations how to do it.

If you were able to reset the protection:
Before reassembling everything, you should try to bring both cells to the same voltage. A good possibility is to use a LiIon-cell-charger with single bays, they know, how to charge lithium cells! If you have one, you can use it to charge both cells seperately to the max voltage (that is kind of "balancing"!). This might also help to check the cells and fill the pack up, but will not reset the protection!

Don't have a LiIon-charger? Too bad.


You reached this point?
I'm glad, that at least one did... :good:
Hope, it helped.
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#30 Aimevous

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Posted 26 June 2011 - 08:52 PM

Hi,

I actually listed my problem in another thread just 12 hours ago but perhaps you can help. My tablet used to have the 1% charging problem and I had thought that my batteries were dead and were prepared to dump it so I cut out the leads and was ready to throw it away but after a few days decided to try it again and soldered it back and hey what do you know? It managed to charge up...albeit VERY SLOWLY.

It takes about 16-20 hrs to charge up the tablet. I am not sure what is wrong and I am thinking if it is the charging circuit. Do you have any advice on how do I test/check what is wrong or what is causing it to charge so slowly?

Thanks!

#31 purplesun

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Posted 26 June 2011 - 09:54 PM

I actually listed my problem in another thread just 12 hours ago but perhaps you can help. My tablet used to have the 1% charging problem and I had thought that my batteries were dead and were prepared to dump it so I cut out the leads and was ready to throw it away but after a few days decided to try it again and soldered it back and hey what do you know? It managed to charge up...albeit VERY SLOWLY.

It takes about 16-20 hrs to charge up the tablet. I am not sure what is wrong and I am thinking if it is the charging circuit. Do you have any advice on how do I test/check what is wrong or what is causing it to charge so slowly?

Can't help specifically, but some ideas I have;
1) Have you tried to charge the battery with the unit completely powered down (hard switch set to off)? Does that charge faster?
2) Are you quite sure the AC chargers you tested are capable of delivering more than 1 amp at 9 volt?
3) Does the camera side of the unit get quite hot when charging? That's where the charging circuit is. Try cooling it down to test if it will charge faster.

Hope this helps.

#32 Aimevous

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Posted 27 June 2011 - 10:27 PM

Can't help specifically, but some ideas I have;
1) Have you tried to charge the battery with the unit completely powered down (hard switch set to off)? Does that charge faster?
2) Are you quite sure the AC chargers you tested are capable of delivering more than 1 amp at 9 volt?
3) Does the camera side of the unit get quite hot when charging? That's where the charging circuit is. Try cooling it down to test if it will charge faster.

Hope this helps.


Thanks for your reply!

1) I have tried to charge with the hard switch off but doesn't seem to charge any faster. Did an overnight charge. Still red light since 10 hours ago.
2) Not sure about the current, cuz I accidentally burnt my multimeter while trying something stupid unrelated to this.
3) Yep it does get warm, but not as hot as I remembered it to be when it used to be working fine.

I wonder if there's anyway to isolate the problem.. shucks.

Edited by Aimevous, 27 June 2011 - 10:28 PM.


#33 purplesun

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Posted 28 June 2011 - 02:46 AM

1) I have tried to charge with the hard switch off but doesn't seem to charge any faster. Did an overnight charge. Still red light since 10 hours ago.
2) Not sure about the current, cuz I accidentally burnt my multimeter while trying something stupid unrelated to this.
3) Yep it does get warm, but not as hot as I remembered it to be when it used to be working fine.


http://translate.goo...fwtPuR3fhC-aIlA

Post #73 of this thread from 4pda.ru talks about component-level repairs to fix the battery charging problem. I can't quite make head or tail with the google translation; but might be what you are looking for. Probably best to get a native speaker to elaborate before attempting the repair.

#34 Aimevous

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Posted 28 June 2011 - 03:27 AM

http://translate.googleusercontent.com/translate_c?hl=en&prev=/search%3Fq%3Dhttp://4pda.ru/forum/index.php%253Fshowtopic%253D227464%26hl%3Den%26client%3Dfirefox-a%26hs%3D4ES%26rls%3Dorg.mozilla:en-US:official%26prmd%3Divns&rurl=translate.google.com.sg&sl=ru&u=http://4pda.ru/forum/index.php%3Fshowtopic%3D227464%26st%3D60%23entry8001723&usg=ALkJrhggwQiK5I4CHrCfwtPuR3fhC-aIlA

Post #73 of this thread from 4pda.ru talks about component-level repairs to fix the battery charging problem. I can't quite make head or tail with the google translation; but might be what you are looking for. Probably best to get a native speaker to elaborate before attempting the repair.


Thanks for the link!
However, it was going on an endless google translate loop. Something is wrong with the embedded link. I managed to pick out the actual link though. http://4pda.ru/forum...60#entry8001723 for those who are interested.

I'll take a look through and see what I can find. Haha time to find/make a Russian friend! :D

#35 Aimevous

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Posted 28 June 2011 - 03:33 AM

Wow, seems like the Russians managed to get a lot of things going on their C8!

Internet via bluetooth, vibration feedback, additional hardware buttons for volume.

Too bad, I can't quite understand what is going on.

Dear Russian friends, can you kindly translate the stuff on http://4pda.ru/forum...60#entry8001723 for the rest of us who can't understand Russian?

I'm sure everyone will be very very grateful!

#36 Danbbking

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Posted 08 July 2011 - 04:39 AM

Wow, seems like the Russians managed to get a lot of things going on their C8!

Internet via bluetooth, vibration feedback, additional hardware buttons for volume.

Too bad, I can't quite understand what is going on.

Dear Russian friends, can you kindly translate the stuff on http://4pda.ru/forum...60#entry8001723 for the rest of us who can't understand Russian?

I'm sure everyone will be very very grateful!


Hi all
I have been trying to decipher the Russian site translation too using online translators.
http://4pda.ws/forum...ic=227464&st=60

post #73 Translation:
The problem with charging, when the plate stops charging itself (usually after a deep discharge) due to failure of the regulating transistor. It dissipates too much power! What they offer - to replace the resistor 0.2 ohm (R200) ​​at 0.33 ohms (R330) . This will reduce the charge current is almost half as much and as many will increase the charging time ... Well and, accordingly, replace the faulty transistor. In the original, it seems worthsi2305ads . You can choose to replace the same IRLML5203 , IRLML6402 ... Surely there are more options. And yet it is interesting that parallel to the existing body of transistor sot-23 is under mounting SO-8! Look for it, you can find there. May not have to solder a resistor to reduce power and increase the charge time. AntonSV Date • 23.06.2011, 18:35 Changing charging not obviate the failure of the transistor in too deep discharge. Ripple at nominal charge relatively large, but not fatal.Breaks down the charge transistor is not because of them. So change is possible only for his own solace. In any case I'm not going. Installing the upgraded firmware, which states "reduced lower cut-off threshold voltage, provides up to 20% battery life" may increase the likelihood of failure of the transistor! It is claimed if the case. And now about the promised replacement for transistors in SO-8 package. Let me remind you, they should change for those who broke down the regulatory body in charge transistor SOT-23. In the case of the transistor in SO-8 than the maximum power dissipation. You can take IRF7204 ,IRF7207 , IRF7406 , and many others. For those who can read the documentation - the selection criteria: the maximum current - not less than 2A, the permissible drain-source voltage (drain-to-source voltage) - not less than 12V, the gate voltage rating -source (gate-to-source voltage) - not less than 12V, the threshold gate voltage (gate threshold voltage) - not more than -3.5 V (in absolute value, ie, 2B - can-5B - not). The remaining options in this application is not very important. Fits this transistor to replace the existing. also see the battery charge controller post has been edited P43YM - 07.01.2011, 10:45 p.m.Posted ImagePosted Image



So it looks like it all keeps coming back to a hardware component issue, with a need to have a particular transistor replaced, (as mentioned in the Russian post above as well as this topic) and in the event of a damaged IC due to accidentally reversed polarity (in Lubo's case), that component replaced too, to improve the charging.

I am confident my charger is not at fault, and I've no heat issues from charging. I am also confident, having used a huge number of Firmwares over the last 8 months, it's not a firmware issue. Some people have experienced this problem weeks after getting their tabs with stock firmwares.

After around 7 hrs of charging with the device off, I get 35-45% which last (with Wireless on) anything between 25-50mins if I am lucky.

I've tried all the battery calibration and a multitude of different states (ie on, off, on with slider switch, off with slider switch, etc), as well as with 3 different chargers.

As per EatatJoes comprehensive post(#29 on 26/6) , among other things, one thing I've taken from it is that perhaps the damage has been done to the batteries after the component fails and repeated charging attempts are degrading the battery.

I think this topic needs to be pinned/stickied since I keep seeing newbies posting the same problem from scratch, resulting in the community having to repeat itself - go over old ground. (Moderators - could this be done please if poss? Thanks.)Posted Image

This is such a major issue as one of the main reasons we all use Tabs is portability. At the moment I have to carry the charger (and it's 2 pin to UK mains adapter) around to use it in coffee shops and pubs! When I first got the tablet I used to have 5 hrs use at least out of the battery.

cheers

DanPosted Image
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#37 eatatjoes

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Posted 11 July 2011 - 04:12 PM

Hi, me again,
as I tested some more things on my good working Dropad, I can tell you this:
inside the battery is a protection circuit, nothing more. This is used in battery packs, that are not "balanced" while charging, but are charged in series, with ~8,3V in our case. 8,4V would be better, but is impossible without balancing the cells.
The charger circuit gives out a fixed current of 1A to the battery, until a voltage of ~8,0V is reached (~20min at my dropad). At that point the voltage is "stable" at 8,1-8,3V until the current is down to 170mA (total charging time ~2 hours). The LED turns green at that point.
If your charging circuit fails, and provides a higher voltage than 8,4V, the protection will cut the connection to protect the battery cells (and you from blowing up your battery). This means, your batteries can not be charged with that circuit anymore. The protection resets, if the source is disconnected and reconnected, but when the voltage rises to more than 8,4V the protection again cuts it.

In my dropad the battery status is allways much too high, even after some tests with "battery calibration", it didn't change anything. Most time, the status is ~15-20% higher than the real battery charge. A status of 30% is in reality ~15% battery charge, so a runtime of ~30min can be expected at a status of "30-40%".

If you want to check it, measure the voltage to the battery, while your power supplies are connected. If it is more than 8,4V the protection will cut the connection. If you now disconnect the power supply, you will measure a very low voltage, maybe 0V. If you reconnect for some seconds and then again disconnect the power supply, the battery voltage is back at 7,xV, meaning, the battery is ok, protection is resetted. But the battery is not charged, only a bit.
But if your charging circuit puts out more than 8,4V, shut down will happen again after some minutes, charging the batt is impossible like that!
The protection is there to protect you from big problems, that will happen, if a charger fails! Be happy it's there!
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#38 eatatjoes

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Posted 11 July 2011 - 04:29 PM

I forgot:
you are very lucky, if your tabs are still working with the power supply. Marcoslongo had an exploded circuit, I saw his picture. There really is a small crater (!) in his board, and the power connection doesn't work at all. He now has a 9V pover supply connected to the battery connection, the only way to make his dropad work, but it's impossible to charge his battery like that.
We are trying to make it possible to charge his battery with an external $10 balance charger, but he then will have a small connector hang out of the back of his dropad. Not nice, but a simple solution.
I tested that on my 'pad before, and had ~20min more runtime, due to simply better charging the cells to 8,35V each!
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#39 eatatjoes

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Posted 11 July 2011 - 04:57 PM

Here is a chart of a good working Dropad charging the battery:

Attached Files


Edited by eatatjoes, 11 July 2011 - 05:10 PM.

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#40 eatatjoes

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Posted 11 July 2011 - 05:12 PM

And another chart of that Dropad, "battery status" and "battery voltage", while Dropad is running, screen on, wifi and battery app for 7 hours:
Attached File  000 - Voltage to charge chart.jpg   61.64KB   23 downloads
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