E-reader Pro Not Responding

[daniel bastida]

Hello, I'm asking for help fixing/rebooting this e-reader.

Brand: Energy System.

Model: E-reader Pro (Boyue T62 clone).

OS: Android 4.2.

Original battery: 3.7V / 2800mAh.

I bought it in this condition, not working, with the fixed "I need battery" screen.

The battery was swollen, for disposal.

I've tried two 3.7V batteries in parallel, but it doesn't respond.

If I connect it with a cable to the PC, it detects a "RockUSB device", but not a disk drive in Explorer.

Before I throw it away, any ideas?

[Quoth]

Never connect batteries direct in parallel, except for large, new, matched Zinc carbon or Zinc chloride primary cells. Even that is rare now.

Especially never connect LiPoly cells in parallel*. They are typically above 3.7V but above or equal 4.2V when charged. If the cell is too low it won't charge, or will only charge very slowly.


"It looks dead Jim!"

Keep screen and any ribbons.


[* Some factory made Li-Ion packs may have pairs of matched cells in parallel. Certainly never ever connect different sizes of cells in parallel even if the same chemistry. Fire may occur.]

[daniel bastida]

[QUOTE=Quoth;4521052]Never connect batteries direct in parallel, except for large, new, matched Zinc carbon or Zinc chloride primary cells. Even that is rare now.

Especially never connect LiPoly cells in parallel*. They are typically above 3.7V but above or equal 4.2V when charged. If the cell is too low it won't charge, or will only charge very slowly.


"It looks dead Jim!"

Keep screen and any ribbons.


I checked that both had a similar charge of 3.8V, and adding amperes, about 2800mAh. I connected them just to see if they would turn on the e-reader... but it didn't.
shame.
Thanks for the reply

[Quoth]

Originally Posted by daniel bastida

I checked that both had a similar charge of 3.8V, and adding amperes, about 2800mAh. I connected them just to see if they would turn on the e-reader... but it didn't.
shame.
Thanks for the reply

But they are obviously different cells and you can't parallel LiPoly directly. Also the mAH is how long the cell can supply power, not the current rating. Even a tiny 450 mAh would power an ereader.

For example, if a 1500 mAh cell gives 20 hours reading time, then a 450 mAh would give about 6 hours and 2800 mAh would give about 37 hours.

The LG pack might be really dead as it's dated 2014.

How do you know those LiPoly cells actually work?

The current rating isn't the issue. Measuring the terminal voltage with no load is also misleading. A 180 Ohm resistor is about 20 mA load, that would be a reasonable test as that might be similar to what a small screen reader takes without any front light, BT or WiFi. If a cell isn't 3.8V or more with a 180 Ohm load, it won't power (boot) an ereader.

Three flat N / Lady, AAA or AA cells is 3V, but 4.8V when fresh (though a nominal 4.5V). They would be good to test the ereader if they read 3.8V to 4.7V on your test meter with a 180 Ohm to 470 Ohm load.

Simple battery testers actually have a built in pair of load resistors for 1.5V or 9V as a digital meter can be misleading about battery/cell condition.

So your ereader might not be dead?

[theducks]

[QUOTE=daniel bastida;4521057]

Originally Posted by Quoth

Never connect batteries direct in parallel, except for large, new, matched Zinc carbon or Zinc chloride primary cells. Even that is rare now.

Especially never connect LiPoly cells in parallel*. They are typically above 3.7V but above or equal 4.2V when charged. If the cell is too low it won't charge, or will only charge very slowly.


"It looks dead Jim!"

Keep screen and any ribbons.


I checked that both had a similar charge of 3.8V, and adding amperes, about 2800mAh. I connected them just to see if they would turn on the e-reader... but it didn't.
shame.
Thanks for the reply

BAD BAD
If there was a shorted cell in the old battery, FIRE
It is not just the RATED voltage to consider. it is the current 'terminal' voltage.

[daniel bastida]

Originally Posted by Quoth

But they are obviously different cells and you can't parallel LiPoly directly. Also the mAH is how long the cell can supply power, not the current rating. Even a tiny 450 mAh would power an ereader.

For example, if a 1500 mAh cell gives 20 hours reading time, then a 450 mAh would give about 6 hours and 2800 mAh would give about 37 hours.

The LG pack might be really dead as it's dated 2014.

How do you know those LiPoly cells actually work?

The current rating isn't the issue. Measuring the terminal voltage with no load is also misleading. A 180 Ohm resistor is about 20 mA load, that would be a reasonable test as that might be similar to what a small screen reader takes without any front light, BT or WiFi. If a cell isn't 3.8V or more with a 180 Ohm load, it won't power (boot) an ereader.

Three flat N / Lady, AAA or AA cells is 3V, but 4.8V when fresh (though a nominal 4.5V). They would be good to test the ereader if they read 3.8V to 4.7V on your test meter with a 180 Ohm to 470 Ohm load.

Simple battery testers actually have a built in pair of load resistors for 1.5V or 9V as a digital meter can be misleading about battery/cell condition.

So your ereader might not be dead?

First of all, thank you for the explanation; it was very helpful.

I've tried other batteries, including 3 AAA batteries, and I've tested them with a resistor... the e-reader doesn't turn on.

I don't think it would turn on with an original battery either.

I don't see a solution. I'll leave it at that.

Sincere thanks.

[Quoth]

At least save the display! You never know!

[daniel bastida]

of course!

[John F]

I'm curious... if one had a variable voltage power supply, could you use that to do some testing of the reader?

[theducks]

Originally Posted by John F

I'm curious... if one had a variable voltage power supply, could you use that to do some testing of the reader?

Why not if it was a clean (no hum or noise) DC?
The advantage is you could also set a current limit, saving traces or wires if there was a shorted component.

[Quoth]

Originally Posted by John F

I'm curious... if one had a variable voltage power supply, could you use that to do some testing of the reader?

I use such a thing regularly, but it's expensive unless you do electronics or repairs and requires some technical knowledge. A decent one costs as much as a good ereader.

[Renate]

A power supply will give you current measuring and you can see if anything is happening.

Don't use two batteries. Sheesh.

Since you haven't even gotten this to work you don't need longevity.

If it's showing "RockChip" then probably the system image is bad and it's waiting for you to rewrite it.
Does this thing use the SD card as its main flash?
If so, then not having an SD card in there will do that.

[daniel bastida]

Originally Posted by Renate

A power supply will give you current measuring and you can see if anything is happening.

Don't use two batteries. Sheesh.

Since you haven't even gotten this to work you don't need longevity.

If it's showing "RockChip" then probably the system image is bad and it's waiting for you to rewrite it.
Does this thing use the SD card as its main flash?
If so, then not having an SD card in there will do that.

With the micro USB power supply, it doesn't work at all.

This model doesn't have an internal micro SD card, but it does have an external slot.

[Renate]

Originally Posted by Quoth

A decent one costs as much as a good ereader.

Yeah, but the future is here today.
A crappy one that uses USB PD can be gotten cheaply.

[Quoth]

Originally Posted by daniel bastida

With the micro USB power supply, it doesn't work at all.

Many ereaders and other things (cameras, phones, tablets etc) that have USB charger won't start at all without a suitable battery.

Some use serial data from a management unit in the cell pack and they won't work with the wrong model of cell (battery) or a bench power supply or via USB at all if there is no compatible battery. Some others have a temperature sensor and some have the serial data and a temperature sensor.