Dyson Vacuum Battery Replacement (2)

The previous article is continued here (embedded below).

The battery of the Dyson vacuum I have been using for about 10 years reached the end of its life, and I attempted to replace it. However, since genuine parts were out of stock, I decided to buy a compatible battery after much hesitation. But, fearing a fire accident, I did some research and found a website called "Gokan Battery.com" (Compatible Battery.com). The previous part of this story ended with me finding that the Dyson compatible battery from a "Japanese company" called Enelife, which I had already ordered on Amazon, was starting to look "suspicious" based on information from this site.

The contents of the suspicious "Gokan Battery.com"

I had been relying on "Gokan Battery.com," but upon closer inspection, I found several articles that were inconsistent and lacked coherence. Looking closely, the illustrations in the articles didn't look unlike AI-generated composite images. The feeling that "this site isn't written by a real person" grew stronger, so I decided to stop taking its content at face value and proceed by verifying things myself.

First, I looked into the company called Enelife.

The company Enelife

The company profile for Enelife can be viewed via the embedded link below.

It appears to be a company run by Japanese people, for Japanese people. However, when I scrolled down to the "History" section of their website, I saw a picture of a battery pack that looked familiar. The next surprise was realizing, "This looks exactly like the AWANFI battery pack!" Comparing details like the patterns, it turned out they were "completely identical."

The Enelife V7 compatible battery currently available for purchase on Amazon is different from this photo, but when compared to the AWANFI V7 compatible battery (though there are minor differences in the pattern), they look almost the same. The suspicion arose that Enelife itself might have a close relationship with a Chinese company. Is it really "Made in Japan"? The "suspicion" has only increased.

Looking at the comments from Google AI (likely Gemini), it explains that Enelife's compatible batteries use a "full-cell + single-cell detection method" protection circuit, but that this alone cannot prevent overcurrent (see the screenshot below). However, be careful, as that content contains errors.

First, it says "fire accidents have been reported in the past," but this is a lie. This is because the aforementioned "Gokan Battery.com" article published an article with a misleading title, and the AI simply misunderstood based on this information. The title of the document the AI referenced is embedded below, and the specific content is in the quoted image below the embed.

It seems the AI misunderstood because the article's title and cover image were about "fire," but the content of the article clearly states that "there are no specific reports of fire incidents." This is what happens when you take what AI says at face value.

So, I decided to make a judgment while actually looking at the contents of the document.

What is the full-cell + single-cell detection method?

I will start by looking into the "full-cell + single-cell detection method" mentioned in the Google AI comment.

Looking at the reference material indicated by the AI, it seems it reached this conclusion because the "AI consumed" the following document.

There are two main types of compatible batteries sold by Enelife: one is Dyson-compatible, and the other is Makita-compatible. Makita is a major power tool manufacturer in Aichi. According to Wikipedia, Makita tools are popular worldwide, with a 25% global market share in power tools (ranking second) and a 60% share in Japan (ranking first). (By the way, the electric brush cutter (so-called "beaver") and electric chainsaw I own are Makita products. Of course, I use genuine Makita lithium-ion batteries for power. It's only been about 5 years since I bought them, and there isn't even a sign of degradation.)

Now, regarding the content of the explanatory article the AI used, it was not about Dyson, but rather an article that disassembled and verified a Makita-compatible battery. However, the AI generated comments assuming that Dyson-compatible batteries have a similar design/structure. Regarding this, I (initially) held the same opinion.

The explanatory article deals with a Makita-compatible 18V lithium-ion battery. Its content reports the results of disassembling the battery and analyzing its structure. First, when the case is removed, the photos show a structure where five cylindrical lithium-ion batteries are connected. It is reported that nothing is written on the surface of these batteries, and basic information such as which country they were made in or which manufacturer made them could not be confirmed. However, it is introduced on the Enelife website that lithium-ion batteries of the same color are used (see the figure below).

Judging from the color, the unknown battery cell is thought to be from Eve Energy (China). As expected, the battery itself was not made in Japan, but in China. I already feel "betrayed" here. However, I had already felt the impression mentioned above that "the shape of the battery pack is very similar between Enelife and AWANFI." From the perspective of having suspected a close relationship between Enelife and Chinese companies, perhaps I should say "as expected" rather than "betrayed."

The important point, "the result of investigating the use of protection circuits" was written as follows.

This explanation is exactly the same expression the AI used in its comments. Since there was a detailed explanation of the all-cell + single-cell detection method in the first part of this explanatory article, I will refer to that below.

In the case of cylindrical battery cells, a sheet-like insulating separator is sandwiched between sheet-like positive and negative electrodes, and the whole thing is rolled into a round structure. Electrolyte is soaked between the electrodes so that only lithium ions can pass through the insulating separator (contact between the electrodes is prevented by the separator). Like a Baumkuchen, it is rolled in many layers, and if each is connected in series, high voltage can be achieved, and if connected in parallel, a large-capacity battery can be achieved (realistically, it is likely a mixture of both).

In the explanatory article, five battery cells are used, and it is said that checking the voltage of each one of these is called "all-cell detection," and choosing only one cell to check is called "single-cell detection."

As an example, consider the case where five cells are connected in series (the same example is cited at the beginning of the explanatory article).

Single-cell detection is a detection method where, out of five cells, only one is representatively measured for voltage (let's say it is 3.5V), and that is multiplied by 5 to assume 3.5x5=17.5V is the voltage of the entire battery. The voltage of the entire battery is also measured at the same time, and if it is, for example, 18.5V, a difference of 18.5-17.5 = 1.0V is detected. Ideally, single-cell detection is judging it as "usable" only when this difference is 0. In the example we are considering now, there is a difference of 1V, so a judgment of "unusable" is made by the protection circuit, and this battery pack becomes "unusable."

Of course, in reality, some error should occur, so a certain threshold is set, and a judgment criterion for allowing use within that range is established. For example, if the judgment criterion is set to 0.1V, a battery with a detected difference of 1V will be "unusable," but if it is set to 1.2V, it will be "usable." The stricter the standard, the "safer" it becomes, but "unusable" will appear more easily, meaning the battery life will feel shorter, which consumers will likely dislike. However, if it is set too loosely, the possibility of causing a fire accident will increase. Therefore, whether to make it loose or strict will be optimized according to consumer preferences (safety-oriented or economy-oriented).

The problem with single-cell detection is that it occurs even if the judgment criteria are strict. In other words, applying it to the current example, it lies in calculating the total voltage by regarding the value of only one cell as the "average value". For example, if we assume the voltage of the cell for single-cell detection is (the same as before) 3.5V, the sum of the voltages of the remaining cells should be 18.5-3.5=15.0V. However, there are ways to make 15V with 4 cell voltages: (a) 4.0, 4.0, 3.5, 3.5V is fine, and (b) 3.75, 3.75, 3.75, 3.75 is also fine. In (a), each cell has a different voltage, but in (b), they are uniform (although there is a 0.25V difference from the cell voltage for single-cell detection, that can be considered a "small" difference).

It seems that the "better the voltage balance between cells," the higher the safety of a lithium-ion battery. In other words, a state where each cell is charged uniformly and discharged uniformly is "normal." Conversely, it is said that it is "abnormal," or a "defective product," if a specific cell is charged high or a specific cell discharges quickly. In other words, the symptom called "cell unbalance" is a state that defective lithium-ion battery products have, where the voltage of each cell has various values.

There are likely various situations where cell unbalance occurs. For example, it may occur because the performance of the insulating sheet between the battery cell electrodes drops, causing it to discharge on its own, or it may occur when the performance of the electrodes drops and the ability to store or release lithium ions decreases. In short, it is a symptom caused by the physical and chemical deterioration of the cell as a battery.

The main reason why cell unbalance is related to safety is that it becomes difficult to judge how much the voltage should be increased during charging. Assuming the durable voltage for charging per cell is up to 4.0V, it is possible to charge cells in a 3.0V or 3.5V state by increasing the voltage by +0.5V. However, a cell that is already at 4.0V will enter an overload state if the voltage is increased even slightly by charging. In this state, in the worst case, dielectric breakdown occurs and an overcurrent is generated. Of course, this becomes the cause of a fire.

If the voltage increase could be controlled for each cell, safety could be ensured, but since a complex circuit would be introduced, the price would likely go up (if a 10,000 yen genuine product became 13,000 yen, consumers would dislike it). If you want to charge cheaply and efficiently, each cell should be charged with a common value. If so, if the voltage of the cells before charging is not uniform, the charging range cannot be determined. This is the reason why "cell unbalance" is disliked.

One might think that even if there is an imbalance, for the sake of safety, it should be set to charge according to the cell with the highest voltage. However, because of the cell that is at the limit of its durable voltage, cells that have values far below the durable voltage will only be able to increase their voltage by a tiny amount, and as a result, consumers will feel that "it can no longer be charged." For example, suppose the durable voltage is 4.0V and a high-voltage cell is 3.9V. To avoid exceeding the durable voltage, the voltage increase due to charging must be kept to 0.1V, but cells in a 3.2V or 3.5V state can only be charged by 0.1V, so the voltage can only rise to 3.3V or 3.6V. Even if the durable voltage was 4.0V, this would only be low-voltage charging, and the battery would run out quickly when using the vacuum cleaner.

All-cell detection is a method of checking the voltage of all the cells, of which there are several. Of course, it is usually assumed that all cell voltages are at the same value, and that is the "normal" state. Single-cell detection is a detection method that takes this state as a "premise." However, in reality, performance differences between cells occur due to "quality variations" that arise during the manufacturing process (it is the same type of argument as in the case of rocket parts).

If you perform all-cell detection, you might find, for example, that they are 3.5V, 3.5V, 3.4V, 3.3V, and 3.7V. If the safe maximum voltage of individual cells is 4.0V, since the fifth cell is 3.7V, you will be able to make a judgment that you must not increase the voltage by 0.3V or more through charging. And if the unbalance between cells becomes too severe, you will be able to issue a judgment of "unusable" in advance and issue a warning to stop using the battery beforehand. In other words, all-cell detection is a necessary method for ensuring safety.

Now, looking at the explanatory article, it says that Enelife's Makita-compatible battery uses "all-cell + single-cell detection." If it were only all-cell detection, one could say it is "safe," but it seems that single-cell detection is also mixed in. I don't fully understand, but in terms of timing, doesn't it mean that it is divided into times when it performs all-cell detection and times when it performs single-cell detection? Therefore, if you are unlucky and cell imbalance occurs during single-cell detection, dielectric breakdown will occur and an overcurrent will be generated I suppose. The explanatory article stated that "under specific conditions, it misses cell imbalance," and I am sure that meaning refers to the situation I predicted above. I cannot imagine at all why they made such a troublesome circuit.

However, the above explanation is an analysis of a Makita-compatible battery pack, and I did not directly disassemble and examine a Dyson-compatible battery pack. The AI arbitrarily assumes that this analysis has universality and can be applied to both Makita-compatible and Dyson-compatible batteries. Of course, that is highly likely, but one should not jump to conclusions.

Therefore, I decided to look through the Enelife website as much as possible to see what kind of technical explanation is provided. I found the corresponding part, so I will post it in the figure below.

It has the nuance of "monitoring every single cell individually." Also, the box on the bottom right seems to mean "all-cell detection." If this is true, I think it supports the fact that Enelife's compatible batteries have not yet caused any ignition accidents. In other words, the conclusion is that Enelife's Dyson-compatible battery has a reasonably safe design. The Google AI's comment feels like it is "getting a bit too ahead of itself and contains a lot of lies."

However, if one aims for a "safer" battery, it seems to be common sense to incorporate a more advanced circuit called a BMS (Battery Management System). I suspect that the genuine product is expensive precisely because of this circuit. Regarding BMS, there are explanations on websites such as the one below, for example.

In addition to monitoring current and temperature, it can also control the equalization of cell voltages that have become unbalanced. I believe Enelife's protection circuit has a "monitoring" function, but no control function. I felt that this is related to the low price of compatible products and the high price of genuine products.

What is a lithium dendrite?

There was an explanation in the Google AI's comment that if an overcurrent flows, there will be heat generation, but the risk of ignition increases because "lithium dendrites" are generated. Finally, I decided to look into this mysterious katakana term.

When I searched, I found two documents: (i) a Wikipedia explanation and (ii) research introductions from the Lithium Battery Engineering Laboratory at Nagoya University. Each contains very interesting content.

However, I found out for the time being that "a protection circuit to prevent overcurrent is introduced" in Enelife's Dyson-compatible battery. At this stage, my interest in ignition accidents caused by lithium dendrites resulting from overcurrent has waned, and I have come to feel that I don't need to worry about it much in this current flow. Therefore, I will omit writing down the content I considered here this time.

However, it might become necessary information later, and the phenomenon itself is interesting, so I will just prepare it so that I can re-examine it later (see the embedding below).

What did I end up doing?

In the end, I also canceled my order for the Enelife compatible battery. A major reason was that it was not "Made in Japan" in the true sense of the word.

However, if I leave it as it is, I will end up ordering a brand-new Dyson vacuum cleaner. So, I decided to search for stock of the genuine product one more time. Then, to my surprise! Information appeared saying that it was in stock!

I ordered it immediately. And it was delivered two days later! I was impressed that Dyson is a truly wonderful company. What I experienced was exactly what my acquaintance had experienced!

Still, it's strange. Why did it say "Out of Stock" at first, but changed to "In Stock" while I was researching Enelife and AWANFI?

When I looked into it carefully, the one that was "In Stock" was a minor version-up product of the one that was "Out of Stock." The part number for "In Stock" was 968670-21, and the part number for "Out of Stock" was 968670-01!

Even if a genuine Dyson battery is displayed as "Out of Stock," if you try searching on Google again, you might be able to reach a minor update product. If you try without giving up, a "New Year's good fortune" might be waiting for you (laughs). Better late than never, I will conclude this article by saying "Happy New Year."