Acer tablet battery

[orbanp]

Hello Everyone,
I have an Acer Iconia One 7 tablet that just stopped turning on, it was just dead.It is working now, but not sure why, and have a number of questions.
The tablet was barely used and fairly new, it was never  on the net.The battery was not discharged, previously I used it a couple of months before.
Not loosing much, I took the tablet apart and suspecting the battery I checked it.There are three connections to the main-board, "+", "-", and a line marked "T".There was no voltage at the connector, but the battery terminals showed 2.7V.There is some electronics directly on the battery cell, it looks like a boost-buck? controller, two tiny ICs a couple of R-C components, and component that looked like a coil.
Just curious what is that circuit on such batteries?
Plugging in the USB charger did do nothing.The battery is a single cell Li-Po battery, 3.7V, 2.8Ah.I charged the battery directly a bit, with a VC-CC PS, babysitting it all the time, bringing it up to about 3.6V.Still the tablet was dead, no voltage at the connector terminals.Plugging the main board directly to a PS of 4V (leaving the "T" terminal out), the boot-screen flashed up for a moment.Increasing the voltage a bit the boot-screen flashed a bit longer.Then I reassembled the battery and the tablet miraculously booted up as if nothing happened.There is 3.6V at the connector terminals when the tablet is running.

Just curious, what happened, a software glitch? Never tried to press the "Reset" button.
Any insight into the above?
Thanks, Peter

[m k]

Most likely "T" is for temperature.
Li-Po should have a protection circuitry.

My guess is that the Li-Po protector had a hickup.
Maybe it doesn't come back.

[retiredcaps]

Did you leave the tablet off via power off or was it in sleep/standby mode?

If sleep/standby, you can download battery apps that show you what installed apps might be draining the battery while it's in sleep mode.  Or your tablet isn't going into deep sleep mode for some reason.

[orbanp]

Thanks for the replies!
The tablet was powered down, was not in the sleep mode.
The circuit on the battery had one "power device" on it, one of the ICs the pins on one  side were all tied to a PCB layer. Probably some FET device.Could not identify the circuit, the IC markings were too short and too cryptic.
I could not find circuit diagram or service manual for this tablet, I did find a service manual for another Acer tablet, it only had a block diagram and instructions for diagnostics software to identify problems.The block diagram only showed a battery, and a battery management IC next to the main processor, but no detailed info on the battery.
Thanks, Peter