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Powering an Android Tablet without a battery?

So I bought my sister this Visual Land tablet about 2 years ago. Eventually both the mini usb and charging port broke off from the logic board as expected from a cheap product. So I have this nice idea of using the tablet as a car nav/entertainment system. simply get rid of the battery and push 5v via a standard cigarette light usb adapter or make one with some 5v regulators and done.

I tried resoldering the charge port. I get 5.23v on random points on the board but I get 0v at the battery with the charging port connected. I pulled the battery and tested the terminals on the board with the charging port connected no battery, 0v at the board and the battery alone is also 0v most likely dead and trash as it sat for 1.5 years in a shoebox untouched.

So I pulled out my homebuilt psu power supply and hooked up the variable output to the battery terminal on the logic board. When pushing 3.7v~ I can get the first splash screen to show up but the tablet shuts off right after. When pushing 3.8v any thing higher the first two splash screens show and android starts to boot but the tablet powers off soon after..

So i decided to risk it and pushed 5v directly to the board. It started up fine and booted into android normally except for the low battery issue and some heat coming from the processor. Maybe a heatsink and rigged laptop fan into the casing could fix that? It shut off normally as if it had a dead battery.

How much voltage doeas a generic android board need? Current?Does the board take 3.7v but since theres no battery it wont boot? How could I fake a fully charged battery? Or could I possibly flash a custom rom? Do you guys need more info? I could provide more pics

Note that the battery is a 3.7v 3500mah li-ion battery with only a positive and negative hookups. Also i took some tape and covering off the battery to see if it possibly had its own controller board. It did have a small  pcb board but it seems that its only "a transfer" board, it takes the power from this cloth like cable and passes it into the wire thru the pcb. Should I try to hookup 5v straight to the battery to test it out? Battery has 0v so it might be useless.

Picture of Powering an Android Tablet without a battery?
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You can use an old cell phone battery for testing as well.
If the battery is 3.7V then you should feed the board from the battery connector with 3.7V.
I suspect your PSU does not provide enough current for a proper boot.

mcarrascoza (author)  Downunder35m1 year ago

Well the variable output has a max of 1.5amps.the fixed 12v, 5v and 3v outputs all have a max of 22amps.

1.5 amps should be more than enough right?

Ive just done something similar with a satnav. I found the battery has its own internal charging / discharge protection circuitry, and was reading 0 volts, as it turns off the battery when flat to protect it. I soldered a usb lead direct to the battery leads and it charges and works perfectly. It doesn't explode as it has its own charge circuit. 5 volts is fine to charge it with, which is the voltage from a usb

Photo on 6-07-15 at 5.34 PM.jpg
pierrevorster4 months ago

I have been doing a lot of Arduino GSM programming and electronics. The main problem is the spikes of current. The voltage must be MAX 3.8 volts to not blow processor and other components, but the trick is to keep a constant voltage (With current available when needed). What I needed was 3.4 volts with 2.5 amp capability. This means:- I used a LM317 regulator with 12V supply. 2 x 4700 uF caps on the 12v and a 224 cap (0,22uF).
On the output at the 3.4V I placed 2 more 4700 uF caps and a 224 cap (0,22uF). This circuit worked like a bomb, and handles all spikes and surges, without damage to any components.

HamzaN317 months ago

i have one just like this tablet and the battery is dead can i replace it or plug in the power directly my old battery specifications are 3000mah 3.7v

i am using a power adapter (output) 5V 2A

what can i do to keep using this tablet

saybee42 12 months ago

did you figure out how to power it?

because i'm having kind of the same problem here.

My cheap Tablets battery and screen stopped working and since it has a hdmi output i figured i could maybe use ist as android mini pc hooking it up to a tv.

my only problem ist that i need to power it somehow since the usb port would be used for a keyboard mouse combo.

My thought would be getting a voltage regulator set it to 3.7v and wire it to the batteries wires on the board an just hook a usb wallcharger up to it.

iceng saybee42 12 months ago

What is your skill set and EE knowledge... ?

The implication is you can solder under water as that is all I have managed to put together from your home page in 3 years and this tag on question...

Please start a new question as it provides for a best answer for someone.

Answers can be tailored to your abilities if we know them.

QQ--AA.bmp
Magicyman1 year ago

If the battery was 3.7 3500mah, then that's what you need to put into the board. I have this problem a lot, you need to find a supply that can get you that kind of power. I would not recommend over-volting a board like that, nor unercurrenting it, this does not end well. There's all kinds of step down boards you can get online, here's a good one on ebay

http://www.ebay.com/itm/251768965445?rmvSB=true

Or if you know what you're doing you can grab some resistors a soldering iron and go for it on your own :)

mcarrascoza (author) 1 year ago

Hmm that might also explain why theres no additional wiring to the logic board itself. All the circuitry must be in the in the battery.I'll post a pic of the circuit board just to confirm.

iceng1 year ago

Do NOT put 5V or more then 3.7V to the LiON battery it could burst explode.

Try to charge the battery with a series resistor 10 ohm 20 watt at 3.7V and see if it holds a charge after 2 hours.