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 
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
, 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!
) 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
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...
Hope, it helped.
Help
% full) i could not get mine to boot and with AC power it once again said 1%.
