The following post was written as part of a question I asked regarding removal and charging of a deeply discharged e bike battery. That thread subject evolved into a question of the safety of charging a deeply discharged lithium battery and someone suggested to post it in this forum for a broader response. Thanks.
I am open to be educated more about the safety subject of lithium batteries.
I like to know what is the difference between a new and an old battery like these that are very low in charge. Why the danger increases so drastically (it seems that is what you are implying) if a deeply discharged cell is recharged? And why this danger remains high even if the battery is recharged successfully the first time?
I watched several more online videos in regards to the dangers of lithium batteries. One of them showed that a discharged battery, apparently, is NOT very dangerous. Only when a battery has a lot of energy and is charged it can be dangerous. So my conclusion is that if a deeply discharged battery that is then charged is inherently more dangerous than a brand new battery, then the difference between these 2 batteries must be that one or more safety feature of the deeply discharged battery must have been defeated or bypassed when it lost its charge.
One of these safety features were mentioned on this thread earlier, which was that the metals in the electrolyte may not fully go back into suspension in the electrolyte and if these metals that have not gone back into full suspension bind together they can cause a short and overheat battery and cause the kind of fire and explosion that was shown in the online videos.
Are there any other safety features of a new battery that is different from a deeply discharged battery that is successfully recharged?
In another one of these online videos it was discussed that they are looking into using an all solid state electrolyte by removing all the flammable electrolyte from the cell and put down a ceramic layer capable of conducting lithium ions but not electrons. Thereby removing the possibility of internal short happening inside the electrolyte.
This is the link to this short but very informative video: https://youtu.be/D3GDdZkN6fg
From the video: "There are a lot of pieces and processes that go into a battery to make it work. If any of those processes goes wrong there is a chance for energy to be released, and the reason that happens really is because the electrolyte inside the battery is an organic solvent and that solvent is flammable. So if the battery can not vent you build up pressure and the electrolyte burns and then it explodes." Another section of the video: "In previous instances of batteries catching fire the cause has been bad welds. A lot of battery pieces are welded together and if you don't have a good weld then you develop resistance, resistance develops heat and heat leads to fire. Other times it has been due to contaminants during the building process. Contaminants were generated, a little bit of metal scraped inside of a machine and that contaminant fell into the cell and that caused a hard short between the anode and the cathode which then generated heat and so on and so forth."
So of utmost importance regarding safety of a battery is how well it was designed and manufactured and not metal suspension or precipitation inside its electrolyte. The cells of the battery that I am working on have Samsung written on them. Is there a way to verify that these are genuine Samsung cells?
So according to the above video the real reason for a battery to cause a fire or to explode is either manufacturing defect or lack of venting which can then lead to THE FLAMMABLE ELECTROLYTE to cause fire. In other words it is the flammability of the electrolytic that is the issue and not incomplete suspension of any metal particles inside of the electrolytic (correct this if you think this is the wrong conclusion). As an analogy think of a can of gasoline, it is inherently flammable and if you heat it up then it can catch fire and explode. So once the electrolyte is charged then it is like a can of gas because it is flammable. There is nothing in the video that talks about metal inside the electrolyte that goes from a state of suspension to a state of precipitation causing short but rather that unintended contaminants during manufacturing process causing such a short.
If what is in this video, put out by Michigan Engineering (I think it is the faculty of engineering of a university), is comprehensive in regards to fire and explosion hazards of these lithium batteries, that leads me to think that a used battery that has been proven to be defect free (no bad welds) and contaminant free (no manufacturing defects from factory) should be safer than a non tested fresh battery from factory especially a lower manufactured battery. The analogy of a used car engine and a new car engine comes to my mind: the used engine has gone through the break in period and is proven to be reliable but until the new engine has gone through the same type of break in period its reliability is an open question.