Battery issue

[Martin Gorbush]

It isn’t only your tablet problem. As far as I know every hardware with AXP288 PMIC will power up when you connect (insert) charger. From AXP288 datasheet it seems that it is powered on when VBUS voltage goes above 4.1V. Then it output power to SoC and if that chip release SLP_SOIX_B pin then power on sequence is continued. It might be possible for SoC to stay in suspend mode but it would require special configuration inside BIOS.

I do not know about any solution to this problem. Only thing what you can do is power down the system when it starts to boot. When you are asked to choose system (if you have dual boot model) press and hold power button for at least 10 seconds and tablet will power down and should stay there.

[Yassine]

Hi Martin

thank you for your answer, what about the charger, i use a Samsung charger, the tablet never charged to 100%, because the charge become very Hot just after 2 or three hour. so to charge to 100% i need more than 8 hour is this normal also ??

thanks for your help

[Martin Gorbush]

I’m not quite sure which Samsung USB Charger do you use. I had some old USB power supply from my previous tablet which is described as capable to output 2A @ 5V. But when I connected it to my new Cube tablet it was realy hot even if it could give 2A current. Then I bought another multi port charger with maximum 4A per port and now it is only hot but not impossible to touch.

From my experience and my knowledge about this tablets PMIC (AXP288) I know that it can take 2A current at 5V from mini USB port (10W). Maximum charging current is 1800mA at 3-4.2V (or max 4.35V under Android OS) which mean about 6-7.5W of power consumption (with 95% efficiency). When you use this tablet it can easly take 1200-1600mA from battery when idle with screen powered on or about 0.8-1A (4-5W) from external power source without charging battery (Note: these measurements aren’t maximums). From this data I can interpolate that 2A current taken from USB port will give about 3200mA @ ~4V outgoing from PMIC (charging + working needs). Therefor if you use this tablet and try to charge it this process will be slower. Nominal charging current is 1800mA which is exponentially lowered when battery voltage achive 4.2V (approximately 90% battery capacity). That would take about 5 hours to fully load battery (0.9*7800mAh/1800mA + 0.1*7800mAh/~600mAh) but when you lower it by 300mA charging process will take about 6.5 hours (0.9*7800mAh/1500mA + 0.1*7800mAh/~500mAh).

[Yassine]

Thanks you Martin for the detailed explain, so no solution i think to reduce the temperature of Tablet except if we charge it in a fridge 😉

we must think about changing the battery with another if it’s possible.

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