I realize this is an older thread but assuming some people might still be experiencing problems, I'd like to post a few paragraphs from the Samsung User Manual for the Galaxy Tab3 7.0. This will likely apply to other Samsung Tablets. In fact, this may -to some degree- apply to any device that is powered with a Li-Ion battery (and I will explain a little about this in a bit).
From the manual:
Battery
Your device is powered by a rechargeable, standard Li-Ion battery. A Wall/USB Charger (Charging Head and USB cable) are included with the device for charging the battery.
Warning! Use only approved charging devices. Approved accessories are designed to maximize battery life. Using other accessories may invalidate your warranty and may cause damage.
Battery Indicator
The Battery icon in the Status Bar shows the battery power level. When battery power is 15% or less, your device prompts you to charge the battery. If you continue to operate the device without charging, the device powers off.
Note: The battery comes partially charged. You must fully charge the battery before using your device for the first time. After the first charge, you can use the device while charging.
Note: You cannot charge the battery using the USB cable and your PC.
And lastly:
Note: If the battery is completely discharged, you cannot turn on the device, even with the USB power adapter connected. Allow a depleted battery to charge for a few minutes before you try to turn on the device.
I realize most of these warnings say "cannot" (example: "
you cannot charge the battery using the USB cable and your PC") and yet some people have posted that they could. Well, this -to me- implies that it means you should not because it will likely affect your battery life or its charging cycle.
Now, a little about Li-Ion batteries... These were considered to be God sent invention in comparison to Ni-Cad batteries... (i.e. the batteries that developed a memory where to avoid a battery short life, one had to fully discharge the battery before recharging it, and when recharging the battery, one had to fully charge it before unplugging it).
Well, it seems that Li-Ion batteries have their own quirky little requirement. This comes by way of a protection circuit that built into each Li-Ion battery and is supposed to serve a dual purpose. One, stop the battery from getting over-charged (otherwise it might swell up, heat up and/or even explode), and two, it is supposed to protect the battery from getting under-charged (meaning depleted below a certain level.
It seems for most mobile devices that operate at or around the 5 volt level, the included Li-Ion battery has its optimum level of performance at the voltage level of 4.2 volts, which it seems to maintain for the majority of the discharge cycle and until it gets to about 15 to 20%. When it hits that level, it actually drops drastically towards the 3.0 volt range. The 3.0 voltage range is the low critical level because it is where that battery's protection circuit actually will shut it down, and hence the reason why plugging it back in might or might not get the recharge cycle to start up again.
The quirky part is that the circuit is designed to keep the battery recharge cycle in the off state as long as the voltage level is under 3.0 volts, UNLESS, the battery was designed to reset that on/off switch by way of some sort of signal. And the signal that is required in most these cases is the design voltage and current (i.e. the amount of power supplied to the charging circuit) as designed provided for by the manufacturer who matched that battery with the device as well as with the device charger it included with it.
So look on the original charger that came with your tablet... Read the output rating in Volts and Amps. And since "Power (in Watts) = Voltage X Current" and since in my case, I see "5 Volts & 2.0 Amps", then you need to supply that tablet with (5 Volts X 2.0 Amps =) 10 Watts of power for it to start recharging. It should be noted that small fluctuations in voltage and/or current are allowable as long as the final power output is equal to approximately 10.0 Watts (and the level of tolerance as to how close to 10.0 watts it must be is part of the design which is dictated by the manufacturer). Meaning (as an example) 4.8 Volts at 2.1 Amps (which equals 10.08 Watts should still be OK.
But it should also be noted that different cables might have a different resistance rating and as such, using the OEM cable that has been optimized for this purpose by the device manufacturer will likely serve you best. Otherwise, your best bet will have to be measuring voltage and current at the mini USB end of the cable which -due to its size- might prove to be quite a challenge!
This is not likely to provide a way to resolve everyone's problem, but understanding the basic may in fact prevent you having to go through the same ordeal if you happen to be lucky enough to get your device to start back up and get recharged.
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