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:
- on Samsung Galaxy Tab A:
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:
echo "1000" > input_cur_limit
- Tab A:
echo "1000" > 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:
We changed the permissions and used
echo "1000" > 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.