Lithium-polymer batteries are perhaps the greatest challenge to a specialist in reconditioning batteries, because they have many built-in safety features that resist any attempt to recondition the batteries. Let me tell you a little about how lithium-polymer batteries work, so that you understand why these safety features are in place.
As the charge in a lithium-polymer battery falls very low, that is to say, below a certain threshold, the internal resistance with the battery itself increases exponentially.
But, what does this really mean?
What it means is that, as voltage within the battery drops, internal resistance within the battery climbs to exceedingly high levels. At such levels, the normal charge delivered by the charger meets with immense resistance, and this immense resistance creates a great deal of heat, which can set the battery and its surroundings on fire. The lower the voltage has dropped, the greater the resistance, and the greater the heat, and therefore, the greater the danger of the battery incinerating.
So, why don't lithium-polymer batteries under normal circumstances explode?
This is because most companies include a safety feature within the battery, so that when the battery discharges to a level that is actually dangerous, the safety circuit kicks in and prevents the battery from being charged at all. While this is a safety feature, and a crucial one, since it preserves whatever device the battery is plugged into (and perhaps a great deal more of your possessions as well) from harm, it still ensures that the battery cannot be used again.
So, how do you recondition a battery with such a safety feature active?
The first thing you need to do is to not use a dedicated lithium-ion charger to charge your battery. This is because a lithium-ion charger will respect the safety feature in the battery, and will probably refuse to charge the battery so long as the battery's residual charge is below the safety level.
What you need to use is a variable charger that can deliver a charge to the battery based upon your settings.
Now, you need to apply power to the battery at an exceedingly low voltage that will increase the residual charge in the battery without heating it up.
Remember that if you apply too much power, the battery will heat up, and if it does so, can indeed set fire to itself or to its surroundings. Apply a very low charge to the battery, and it goes without saying, that while doing so, you need to carefully monitor the battery for signs that it is heating up. If you find it heating up, you simply need to halt the charging process at once until the battery cools down. Once the battery cools down, you can proceed with the charging again, only this time lower the voltage considerably so that there is less danger of the temperature rise repeating itself.
Continue to do so until the battery has sustained enough of a residual charge so that it is above the threshold and will charge normally.
It is possible to restore about eighty percent of failed lithium-ion batteries in this way. For additional safety, you can place the lithium-ion battery that you are reconditioning in a fire-proof bag so that it cannot cause any harm in any case.
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