Well indeed there is. We've come full circle.
"Well indeed there is" is hardly an invitation to "move on", now is it?
We're attempting to have a technical duscussion, so objectivity should be present. Which means, when a statement is made, it should be able to be backed up with reference (otherwise it's a opinion, which is subjective). If an inaccurate or incorrect statement is made, it's more helpful to cite a reference than just claim a statement is and say "lets move on".
Lets define over-charging:
"Overcharging occurs when a battery is charged to a higher than specified voltage."
And how do you get the terminal voltage higher? You first have to eliminate current limiting, with the result being a higher voltage. ANY proper current limiting will prevent over-voltage. Without current limiting the terminal voltage, after charging to the correct level, will continue to go up. If you simply regulate the terminal voltage to the maximum permissible, you have, in essence, provided a type of current limiting, though excessive cell heating will likely still result.
Now lets define the cause of li-ion explosions:
"Why Li-ion Batteries Explode" (important reference from this link is below)
"Normally, it’s a manufacturing defect, and apparently that was the situation with the Note7 phones. But the underlying issue is that Li-ion batteries contain a lot of energy in a compact package—which, of course, is why they are used in everything from phones to Tesla electric cars.
A Li-ion battery has an energy density of up to around 160 watt hours per kilogram (Wh/kg), roughly twice that of a fresh alkaline battery or a NiCad rechargeable battery. To produce that power it relies on three main components: the positively charged cathode, which is made of metal oxide, the negatively charged anode, which is made of graphite, and the liquid electrolyte—a solvent containing lithium salts—that enables the electric charge to flow between the two poles.
Like two troublemakers in a grammar school classroom, the cathode and the anode need to be physically separated. Lithium-ion batteries accomplish that with a permeable polyethylene separator, which can be as little as 10 microns thick. As batteries improve and engineers try to pack more power into a smaller package, that thin plastic separator is taxed to its limit.
“The separator has really gotten thin,” says Isidor Buchmann, founder and CEO of Cadex, a battery equipment manufacturer that also runs the educational website Battery University. “And when that happens, the battery becomes more delicate.”
When the separator is breached, it causes a short circuit, which starts a process called thermal runaway. According to Abraham, this is one of the major ways that fires begin. The chemicals inside the battery begin to heat up, which causes further degradation of the separator. The battery can eventually hit temperatures of more than 1,000° F. At that point the flammable electrolyte can ignite or even explode when exposed to the oxygen in the air.
Will these catastrophic failures, rare though they may be, spell the end of the Li-ion battery? Not likely, says Buchmann. While safety is a concern, it’s just one of a number of factors in battery design. Most of the others are related to energy density, battery life and charging performance."
Notice that overcharging is not mentioned specifically, and that's correct, it's not the usual cause, but it is a cause. Here's the reference for that:
"In a lithium-ion battery, overcharging can create unstable conditions inside the battery, increase pressure, and cause thermal runaway. "
(from
Is it Ok to Leave a Lithium-Ion Battery on the Charger? And Other Forklift Battery Charging FAQs)
I already responded to what you repeated, in post #10, explaining why there is a current limited, Constant Current phase of charging.
As to post #10, there are plenty of inaccuracies there to deal with.
"Charging at the maximum (i.e. a 4.2V supply with sufficient power to deliver the current draw at the battery's resistance, V=IR applies) it'll probably get hot, but is very unlikely to explode or catch fire."
If you regulate the charging voltage to the correct maximum terminal voltage you have just applied a current limit as well. And "unlikely" also means "could".
"What causes lithium chemistry batteries to fail catastrophically is overcharging, which results in the production of hydrogen gas in the pack. Eventually the pressure causes rupture, the battery shorts, and the full energy of the battery is released quite spectacularly."
Overcharging is only one cause, and not the most common. In fact, overcharging is one method that can induce thermal runaway. I've already posted links that clear up this inaccuracy.
"Current is limited generally to 1C (1x the rated capacity in mAh, in Amps – i.e. a 3000 mAh cell optimally charges at 3000mA rate, charging in about an hour). This is to preserve capacity, mainly, and cycle life. There are rapid-charge applications that used exactly the same cells but charge at 3-5C, sacrificing pack life in favor of expediency. These packs are simply replaced (a lot) more often. EMS applications are an example. While the cell can probably charge much faster, the reason the BMS limits charging current primarily preserves capacity, not for fire prevention."
We go back to "Why do li-ion batteries explode/catch fire.
Here's a reference that deals with the real cause of li-ion fire:
"Why do Lithium Batteries Catch Fire?
Most fires that occur from lithium batteries are due to thermal runaway. A thermal runaway happens when conditions are met that cause reactions to occur and cannot be easily stopped. These reactions are exothermic, meaning that they give off heat, and that heat may be enough to cause a fire.
We know that physical damage or electrical abuse, such as short circuits, overcharging, and exposure to elevated temperatures, can cause a thermal runaway. Additionally, manufacturer defects, such as imperfections and/or contaminants in the manufacturing process, can also lead to thermal runaway.
Thermal Runaway in Lithium Batteries
During thermal runaway of battery, a reaction can occur, which vaporizes the organic electrolyte and pressurizes the cell casing. If, or when, the case fails, the flammable and toxic gases within the cell are released. Once a thermal runaway starts, the process cannot be stopped, even by unplugging the battery. Even worse, you may not know when this runaway starts. Therefore, it is best to make sure that the battery is being charged in a safe place where other fuels will not be ignited.
To minimize the possibility of thermal runaway the battery, charger, and device manufacturers use battery management systems to make sure that the batteries are operated within a voltage, current, and temperature range that is considered safe. For example, if a lithium-ion powered device says the battery is dead and the device will not operate, the actual battery is not dead, instead, it has reached the lower level of safe operation and a good management system will not allow the use of the device."
The above reference outlines the real and common failure mechanism of a li-ion battery. The bold sentece above shows that thermal runaway is possible without proper and safe charging.
Lack of current limiting is one potential cause of thermal runaway, because to limit current in a way that controls the cell temperature you must also regulate terminal voltage.
Thermal runaway is the acutal root cause of li-ion fires.
A provable improper charging design that produces excessive heat becomes the cause of thermal runaway, which is the cause of fire. Li-ion battery fires have already caused 66 fires and five deaths in NYC alone as of August 3, 2022. The totals are no doubt much higher for the global scope.
Reference here.
Now, if you're an OEM, and designing any product with a li-ion battery, your legal department will have something to say about your excessive heating charging circuit once they've received the law suit citing liabilitiy for a death. And now, your BMS is all about controlling liability, and preserving battery life becomes secondary.
What's not in the news is fires caused by exploding drone batteries. Or are they? A quick google search turned up this:
But, frankly, it is one story. And while not the only drone battery fire on record, drone battery fires are far fewer in number than e-bike battery fires and electric car battery fires currently in the news. But they are still a non-zero risk.
This might be useful to some, re: battery use and care information.
I'm all for moving on, but not at the expense of accurate information so that all here may learn. Myself included.