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Fixing a Dead Li-Polymer Tablet Battery by Over Voltage Answered

Hello all,

I find this Instructable https://www.instructables.com/id/How-to-Fix-Dead-L...

I need to use this method for a Pegatron battery G6BTA019H P/N:0B23-00E00RV

https://i.ebayimg.com/00/s/MTIwMFgxNjAw/z/EkIAAOSw...

but I can't find a diagram of the pinouts for it, would it just be a case of connecting the very end wires, labelled + and -?

How risky is that if it's wrong?

Is there a way to test them with a multimeter?

Thanks

Discussions

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SFS88

6 months ago

This is extremely dangerous, the overvoltage technique was applicable to NiCad/NiMH batteries only. Basically, Nickel-metal batteries, when over-discharged, can grow little metal whiskers or "dendrites" between the internal plates, shorting the cell out. Applying a high voltage to the cell causes enough current to flow that the dendrite fuses and melts, and therefore, the cell is not longer internally shorted, and can hold a charge.

Lithium batteries have a completely different chemistry and construction, overvoltage can cause the production of metallic lithium within the cell which can ignight just from the moisture in the air.

What your seeing in that post is a multiple cell battery that has an integrated management unit, likely what has happened is the cell voltage has dropped below a safe value so the management unit is preventing charging, in theory it is possible to move round this my applying a correct voltage with controlled amount of current to each cell to bring the battery back to a point where the management board will permit charging, however this safety feature is in place for a reason as an such voltage drops could be caused by a defective cell whose internal resistance has decreased in this case the battery is next to useless.

Lithium batteries are simply not worth the risk to your health and property to mess around with... Just ask this guy: https://www.helifreak.com/showthread.php?t=194957#/topics/194957?page=2

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Downunder35m

6 months ago

Let me start with batteries like yours...
It is evident that there is more than just a positive and negative connection.
Means it could be connections to different cell combinations, inside or outside control and safety features and so on.
Messing with those without knowing what is what and what exactly is inside can be quite dangerous.

Overcharging of lithium cells....
You find this a lot on the web and usually only as a way to "fix dead" batteries.
It is true that a controlled voltage spike can get a dead battery back to a state where a charger might accept it.
But this "knowledge" was just taken from the old lead-acid batteries.
Lithium cells undergo chemical reactions of a different kind!
In the worst case nothing will cause any voltage to go through such a bad cell without destroying it.
-But lets be nice and assume you could actually access the real battery connections and apply you direct power shock:
The cells are without any usuable charge, so the lithium and other chemicals are literally used up.
Most of the cell won't even be able to take any charge.
The areas that still do however will change the chemicals and lithium in that area.
This process in a good battery is very even and uniform.
As a result you can end up with what I like to call charge pits.
Small areas that hold a charge long enough to allow a normal charger to take them on again.
You face two big risks:
1. The individual cells will be at different levels of failure.
Through that it becomes impossible to charge the individual cells evenly.
See it like several different resistors in series: The lower resistance in some causes heat to build up and the chemical reaction to go out of control.
Far too simplyfied but you get the picture.
2. The charge pits can grow out of control.
Imagine you pump more and more energy into a cell that can only utilise about 20-30% of its chemicals and metals.
So called spikes can not only form by bad battery design and failing protections but also really good in those pits!
The chemical reaction should cause a gradual build up of fresh material that is your available charge.
It is like growing mountains - you want them to be as flat as possible to get the most charge without the tops breaching the insulations and causing a short.
Ever seen some of these videos where lithium batteries go up in flames while charging? ;)
This happens once a spike has pierced the insulation and reached the opposite pole.

The only half secure way would be to try something with every single cell of your battery.
Chances are it will never get to a decent capacity anyways.
Plus you still risk bad failures in the long run.
IMHO the best and safest option is a replacement, especially if the battery is quite old or had a lot of charging cycles already.

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PlexusIndustriousDownunder35m

Reply 6 months ago

Thank you for that comprehensive reply, I understand enough now
to appreciate that it's not worth the time, and especially the risk of
attempting to revivify the battery. I would replace it, but cannot find
it for sale anywhere. My only option then is to leave it as is, or pay
$160 for the manufacturer to replace it. Which is rather a lot for a
battery. Thanks again though, maybe that Instructable link I referenced
should contain a more detailed explanation like the one you have kindly
provided.