I remove the actual batteries, keep the control board from the batteries (it has a thermistor and sometimes other smart chips depending on the model), and power via the actual battery tabs on the original battery control module via some 12V to 4V adjustable DC-DC buck converter (LM2596).
I remember that once modding a Huawei (worst in the world, cannot be rooted, locket BL, sh*tty firmware) that I bent the battery which was glued to the case with the strongest glue in the world and it started swelling, took it out that moment, and toss it as far as I could control board included, back case included. Then the tablet would boot if powered but kept shutting down instantly with “Battery error”. The battery connector has 3/4 terminals Vcc, Gnd and a thermistor pin, just put a resistor there to emulate the normal temperature for the missing battery and it kept working ever since.
Another funny story with a Samsung this time, using all original board, set the reg voltage to 4.08-4.1V so tablet boots up and shows something like 97% Bat, then after an hour or so it goes to 50% ?!? Check voltages, all good, 4.1V, WTF? It has some sort of a sh*tty software counter which shows the battery as running down even though it’s wall powered, that counter is baked into the hw somehow (changing roms doesn’t solve it). What I did was use Tasker (thanks God Samsung is rootable) to run “dumpsys battery set ac 1” at boot and then the she’s always happy running forever.
LE. I use a small arduino ProMini 5V in each of them to give them a power on signal on the power button pins at powerup (simple sketch like: wait 5s, apply a 500ms low pulse to boot it up, wait forever), much more reliable than software automatic boot tricks and cheap too ($1 per ProMini)
I read, that wireless charging is not safe for 24/7 charing, it should get very hot.
It was my first option for wall mount tablet and charing, but maybe I should use USB-C Flexcable instead, but my idea is, to take the tablet from the mount any time.
The heat generated by any electronic device (phone, tablet, wireless charger, USB power bank, AD adapter, etc.) is due to the fact that energy transfer/conversion is never a 100% efficient process. When you have inefficient energy transfer, most of the lost energy becomes heat. Last I heard, it’s generally about 80% efficient, and 20% lost energy (but I haven’t looked that up in a long time).
If a tablet is constantly trying to draw max power from a wireless charger, it’ll generate a lot of heat. And if it keeps doing that, the heat will build up. That’s usually bad for a device’s battery (and electronics). So in these cases, 24/7 wireless charging would probably be unsafe.
Some newer wireless devices and chargers have temperature sensors and maintenance modes to manage the heat. So they’ll turn on for awhile, then turn off when there’s too much heat (I’m oversimplifying). However, if you use a 3rd-party wireless coil that plugs into a USB port, the tablet won’t know any of that. As far as it’s concerned, it’s just a USB cable. So it might be fine, but it really depends on how the tablet consumes power. And even if it’s good, it has no idea that there’s a wireless charger generating heat next to its battery.
So yeah, it depends.
Personally, I don’t recommend this. If you’ve got an old tablet or phone laying around, just repurpose that as a permanent fixture. That way, your OH information screen is always where you expect find it, and not sitting on a table somewhere with a dead battery.
Speaking of batteries, if you use an old device you should regularly check to ensure that they aren’t bulging at the seams. When that happens, those batteries are a fire risk and should not be charged.
Thank you for your answer. I will load my tablet via usb-c flexcable, first I will try a wall mount with the option “take from wall”, the only “negativ” thing is, that I have to unplug the usb-c cable and plug it in again after put back my tablet
Maybe you are right, and I will upgrade to “fix wall mount” after some time
Depending on what I read and you wrote, wireless charging is very dangerous for old devices, alias “wireless pads”, especially near the battery.
I guess I would say that it’s dangerous to modify electrical devices in ways that they were not intended to be modified. I know more about electronics than the average person, but I’m not a technician or engineer so I stay within my comfort zone. Perhaps its better to say that wireless charging with old devices can be unpredictable.
Any charging tech progress after while?
Should it be some software sleeping mode with motion sensor function to activate display - to maximize battery life of tablet?
As read above removing battery and DC supply could be tricky and damage hardware…
At the moment Iam looking to buy a tablet and do not know if better to look for easily accesible to remove battery or easily configurable with software (rooting device)
control board included, back case included. Then the tablet would boot if powered but kept shutting down instantly with “Battery error”. The battery connector has 3/4 terminals Vcc, Gnd and a thermistor pin, just put a resistor there to emulate the normal temperature for the missing battery and it kept working ever since.