For the gift, start research and development of graphene batteries

Chapter 73 Charge three times a year

The safety and performance of batteries are inherently contradictory.

If you want to pursue safety in the battery, it is safest to have no electricity at all. Even if the battery is burned, it will be fine.

The performance of the battery reaches the limit, that is, the energy density is infinite and the energy is very high.

With so much energy accumulated, it is very difficult not to cause a fire accident in the event of a short circuit.

There is no way to use ternary batteries as passenger car batteries.

Because only the ternary battery with the highest energy density can achieve the longest cruising range at this stage.

As for security, only certain compromises can be made.

Since thermal runaway will catch fire, I will not let the battery suffer from thermal runaway.

The battery itself has limitations, so it is necessary to reduce this risk through the structural design of the entire battery pack and the design of the battery management system.

But in any case, the safety of the battery itself is there.

According to Xia Guo's current level, all ternary batteries cannot meet the cell acupuncture test, and only lithium iron phosphate batteries can pass.

This is why commercial vehicles such as buses must use lithium iron phosphate batteries.

After all, this kind of public transportation is extremely prone to stampede and other data, and safety must be the first priority.In addition, the space of the bus is relatively plentiful, and the energy density of the battery is lower, so it will have little effect if you install more batteries.

The same is true for carbon-based batteries.

It stands to reason that such a high energy density has exceeded too much in terms of performance alone. Regardless of safety tests such as acupuncture experiments, this energy density is also worth using.

After all, this is the case with ternary batteries.It can't pass the safety test, but in the field of passenger cars, it is not widely used.

In fact, when Wang Mingyang saw the item of energy density, he did not require the safety test.

The energy density of carbon-based batteries is already high enough that this problem can be ignored.

Moreover, with such a high energy density, there is a high probability that it will fail the safety test.

Although Wang Mingyang thought so, Jiang Ming had a different opinion.

As a person in the new energy industry, Jiang Ming was very saddened by the frequent fire accidents.

At present, Xia Guo has a huge reserve of new energy vehicles, and corresponding fire accidents also occur frequently.

According to gossip statistics, there are currently about 10 new energy vehicles spontaneously igniting across the country every day, which is quite a high proportion.

Maybe for others, 10 is just a probability number, but for every driver and every family, it is 100%.

Even, Jiang Ming heard that a few members of the family did not run out and were burned alive in the car.

Looking at this tragedy, Jiang Ming felt heartbroken.

Before Jiang Ming didn't have the ability to change anything, he just had to do his job well. Now that he has this ability, if he doesn't think about changing, Jiang Ming can't do such a thing.

The safety test, according to the general standard, is to test six items: overcharge, overdischarge, short circuit, extrusion, hot box, acupuncture.

Overcharge, charge the battery to 10V without protection, the standard is no fire or explosion.

It should be known that the upper limit voltage of the general ternary battery is about 4.2V. If it is charged to 10V, then the battery is abused. In this case, the safety of the battery can only be guaranteed if there is no fire and explosion.

Compared with overcharging, overdischarging is simpler. Put the power of the battery directly to 0V, and the standard is no fire or explosion.

In fact, Jiang Ming felt that this test was meaningless.

Ordinary battery cells are out of power, so how can there be problems with fire and protection?

The only thing to consider is that during the process of over-discharge, metal is precipitated, which punctures the battery diaphragm and causes an internal short circuit.

This may still be the case in the early years. In recent years, this situation has gradually decreased, and the performance of the battery has become very stable.

This is even more true for carbon-based batteries.

Short-circuit test, short-circuit the positive and negative poles of the battery cell directly with copper wires to release the energy of the battery, knowing that the battery has no static position.

Along with the short circuit, I saw that the copper wire used for the short circuit was burned red, as if it was about to be melted.

And as time goes by, the copper wire becomes more red and shiny.

"This"

Looking at the situation in the test box, Jiang Ming frowned.

Something is wrong, the short-circuit energy is too high, even though the standard copper wire is used, it still cannot withstand the impact of the short-circuit current, and the copper wire is about to break.

Looking at the batteries used for testing, they are also slowly expanding as the short circuit progresses.But looking at the state of the battery cell, it seems that it will not be able to discharge the energy for a while.

"Could it be that the energy of the battery cell is too large, and the copper wire can't carry it?"

Jiang Ming was thinking about it.

"Snapped!"

With the continuous release of battery energy, the copper wire used for short circuit was disconnected in the middle.

Looking at the traces of disconnection, it was fused abruptly.

Everyone present was dumbfounded watching this miraculous scene.

Even the testing technicians were dumbfounded.

Have you ever seen a short-circuit test that could burn out the copper wire, but the battery was still intact?

The energy of the battery is too much, right?
"Replace a new thicker copper wire, and then replace the battery cell."

Wang Mingyang ordered.

The short-circuit test is interrupted, and new batteries and copper wires need to be replaced to start again.

I saw the technicians quickly replaced the new batteries and copper wires, and started the test.

The new copper wire is twice as thick as before, and it is not so easy to be burned. Even if the wire harness becomes red due to the high current, it is still intact in the end.

Everyone's eyes were fixed on the battery cell in the test box, watching the battery cell change from the previous level to the current failure.

At this time, the battery cell seemed to be inflated, bulging, and looked like it was going to explode at any time.

Of course, this is just an appearance, and the battery will not explode anyway.

Because the explosion-proof valve at the top of the cell has been flushed open at this time, the high-pressure gas inside has been released.

The bulge seen now is just the expansion of the internal material and the deformation of the battery case caused by stamping. In fact, the battery has no energy inside.

Seeing that the short-circuit test passed, Jiang Ming also breathed a sigh of relief.

A lot of batteries are stuck in the short circuit test.

This is especially true for carbon-based batteries. With such a large current and such a high energy, the risk of thermal runaway is high.

The next extrusion, hot box, although it is a safety item, but as long as there are no major defects, there is no problem in passing.

This is especially true for carefully engineered carbon-based batteries.After passing, there is no problem at all.

Next, came the highlight, the acupuncture test.

Everyone's expressions became serious, because everyone knew that this was the key item.

Although the acupuncture test could not pass, it would only affect the use in some fields, but if it could pass, it would definitely be a historic leap.

The battery cell was fixed, and the 5mm-thick steel was driven by the machine at a speed of 20mm/s to probe towards the shell of the battery cell.

near, near.

"Snapped!"

The sharp corner of the steel needle collided with the battery case, making a sound.

"Stab!"

Next came a screeching sound.

Don't get me wrong, it's not the sound made by the steel needle piercing the battery core, but the sound made by the gears of the machine when the steel needle is held up by the battery core and the steel needle cannot go deep.

Seeing that the steel needle has been turning there, but it can't go deep, the technician quickly stopped the machine.

It won't work if you keep going, if you continue like this, you don't know if the battery is working or not, but the machine will definitely be useless.

"Old Wang, do you see?"

The technician pointed to the position where the battery cell and the steel needle were in contact, and looked at Wang Mingyang.

I saw a small spot where the two sides were in contact, where the steel needle was about to go deep.

The dot is very shallow, and if you don't look closely, you may not see it at all.

"Jiang Ming, do you see?"

"It's too hard, change to a stronger steel needle."

Jiang Ming glanced at it and said so.

At present, it is because the shell of the carbon-based battery is too hard, so ordinary steel needles cannot pierce the shell, and cannot cause an internal short circuit.

Jiang Ming remembered watching a video before, saying that if someone is interested, he is going to test CTAI's star product: 811-ratio batteries.

This time the test was mainly conducted through acupuncture experiments to verify whether the battery cells could pass this safety verification.

The idea is good, the test equipment is no problem.

However, because of CATI's battery cell, the shell is too smooth, and the hardness is relatively high. The thick steel needle does not pierce the battery cell.

According to this UP master, CATI’s 811 matching battery is very safe, and there is no problem in passing the acupuncture test.

At that time, Jiang Ming burst out laughing, thinking that the UP owner could not have taken money and came out to be funny.

You know, the acupuncture test is to cause the battery to undergo thermal runaway through artificial short circuit, and then observe the changes in the battery.

You didn't even pierce the battery casing, what kind of needle prick.

As for whether the shell is smooth or hard, that is another matter.

There was a lot of trouble at the time, with many netizens watching, it was very lively.

The most important thing is that many netizens overwhelmingly support the UP master, thinking that there is no problem with his test.After all, it's very safe if they can't be stabbed.

If it wasn't for Jiang Ming or someone in the circle, Jiang Ming almost believed it.

Now Jiang Ming and the others are testing carbon-based batteries, and they also encountered this problem.Naturally, Jiang Ming and the others would not do such a thing as cheating. They would directly replace the steel needle with a thicker and harder one to see the real reaction of the battery cell.

The so-called collision between strong and strong depends on who will soften first.

呲!
Sure enough, being strong is the last word, and the steel needle is advancing towards the battery case at a steady speed.The hard shell can't stop the advancement of the steel needle in the slightest.

Stab it!

The moment the steel needle pierced the battery case, there was a sharp sound, which made people's brains hurt.

Accompanied by the sound was a puff of white smoke, and this puff of white smoke became stronger and stronger as the steel needle went deeper.

Jiang Ming's expression was gloomy and uncertain as he watched the starlight that pierced the entrance with steel needles.

The steel needle completely pierced into the battery cell. At this time, the internal structure of the battery cell was destroyed under the action of the steel needle, and the inside of the battery cell was in a frantic internal short circuit.

Along with the short circuit in the battery cell, the thick smoke generated by its side reaction rose up and filled the entire testing space.

Jiang Ming knew that the battery cell testing had reached a critical moment.

Although the current state of the battery cell is still stable, there may be higher energy gestating inside the battery cell, waiting to soar into the sky.

Laymen may not understand why new energy vehicles and lithium batteries are so powerful when they catch fire.

After all, with the same volume, lead-acid or other batteries do not have such a big reaction, and lithium batteries alone are special.

Moreover, in a closed space like a battery box, oxygen is limited. When thermal runaway occurs, the oxygen will be consumed quickly, and the battery should not experience a wider range of thermal runaway.

But the reality is that the more confined the space, the greater the chance of the battery exploding or catching fire.

This is actually a special mechanism of the reaction involving lithium batteries.

It is common sense that the combustion of a flame consumes oxygen.

Like normal fires, as the limited oxygen is consumed, the size of the fire is reduced accordingly, and ultimately nothing can be achieved.

But lithium batteries are different. The combustion of lithium batteries will generate oxygen by itself.

And as the reaction intensifies, the oxygen produced will increase rapidly.

Oxygen is the standard configuration of the three elements of combustion, and the act of producing oxygen by itself is like adding fuel to the fire.It really is the fire borrowing the wind, and the wind aids the fire, and it can't be controlled in an instant.

The battery cells that had been pierced by the needles were quietly staying in the testing room at this moment, and nothing unusual could be seen.

Even, the thick smoke from the batteries is much smaller than before.

The smoking machine is working hard, sucking away the annoying eyes.

Jiang Ming looked at the batteries in the middle and felt that something was wrong.

At this moment, the position where the electric core needle touches is still a little bit of sparks.Like charcoal being ignited, it exudes red light spots.

After almost half an hour, there was still no change in the internal battery core, and white smoke was still emitting.

Looking at the time, the technician felt that it was almost done and was ready to end the acupuncture test.

Because according to the current situation, the battery core should not burn anymore, and the acupuncture test passed this time.

Just as the testers were about to announce the end of the test and the test passed, suddenly, a puff of white smoke emerged from the batteries in the test room.

Accompanied by the white smoke, there is a large amount of red light.

"No, it's going to burn."

Although through the glass window, he knew that the power of the battery burning would not hurt everyone, but Jiang Ming subconsciously pulled everyone back.

"puff!"

Thick smoke and sparks filled the air, and the next moment it was a fire that soared into the sky.

At this moment, the carbon-based battery is still on fire, and the burning speed is much faster than that of ordinary lithium batteries.

A huge battery, from the beginning of burning to the end of burning, only took less than 5 minutes.

Seeing the raging flames, Jiang Ming fell silent.

Although he knew that the carbon-based battery might not pass the acupuncture test, Jiang Ming couldn't help feeling a burst of regret when he saw the carbon-based battery burn.

Especially seeing the soaring flames, which seemed to swallow everything, Jiang Ming's face was even more gloomy.

"Change, must change!"

Jiang Ming thought of this in his heart.

(End of this chapter)