Forcing higher USB current The big problem: Like a lot of people, we are finding that our tablet does not maintain charge when connected to USB (PC or other device, not AC jack, we need data and charging simultaneously). 

What has worked so far:  On two tablets, we have been able to successfully force the tablet to draw a higher current by writing a higher value to the files 


on Acer Iconia Tab 8: /sys/devices/pci0000:00/0000:00:18.1/i2c-1/1-0035/power_supply/smb34x-usb_charger/
on Samsung Galaxy Tab A: /sys/devices/soc.0/i2c.65/i2c-13/13-0066/max77849-charger/power_supply/max77849-charger/


on those tablets in the above directories, after setting the appropriate permissions (Acer: chmod 777 input_cur_limit, Tab A: chmod 777 current_now) we can change the USB charge current by writing to the files with the commands: 


Acer: echo "1000" &gt; input_cur_limit
Tab A: echo "1000" &gt; current_now


This works great on these two tablets.  An inline meter on the USB shows the current going higher (close to 1000mA, or whatever we specify) and we are not frying anything (PC, OTG device, tablet) and when the battery fills up itself regulates to a lower value.  All good. 

The Problem now: We have a new tablet. The Samsung Galaxy Tab 4 - 7" (also tried on an 8" with the same results).  

We found the file we thought we should modify: 


current_now in sys/devices/platform/3.i2c/i2c-8/8-0049/power_supply/sec-charger


We changed the permissions and used echo "1000" &gt; current_now to try and modify the file and nothing happens. It keeps returning instantly back to 450 and the meter reading does not go up.  

Any ideas? It worked on the first two devices we tried, but not on these last two (Tab 4 - 7" and 8").  Maybe someone has a completely different method?  Maybe there is another file to change (we have tried several other similarly named files). We understand that this breaks the USB 2 spec, but we need to charge the tablets and send data at the same time.
This is to point out a possibility of replacing echo option, with a copy paste option

( Before that, here is a similar search Prevent complete charging?. .)

Related efforts  and success for AC charging by replacing the file itself, when echo was not possible, (for reasons I still don't know) is my answer for Honor 6 phone here How do I override charging current on Huawei Honor 6?. 

On a side note, similar effort for Samsung Note 2 https://android.stackexchange.com/questions/127288/over-ride-charging-current-on-note-2-n-7100 has not yielded a solution. Unconfirmed views are :


Kernel alone can do that for this phone (from two kernel chefs who made kernels for this phone)
Chipset limitations. This from a developer


Since their views are based on email, cannot quote names

All the best and will be looking to find if there is yet another way