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We catch the degradation of AA and AAA batteries at currents of 0.3 from the capacitance

Two years ago, I discovered a wonderful new world of battery chargers. And even, as far as he could, structured his knowledge in the topic “ We charge AA, AAA and other cylindrical and battery-powered ”. After writing the text, I was tormented for a long time by one unresolved problem - which currents correctly charge the batteries. It is considered reasonable to charge the banks with currents of 0.1 from the capacity. Moreover, both old NiCd and modern NiMh. Allegedly, this is how we postpone degradation.

Firstly, this approach takes a lot of time - currents are too low, the charge takes a long time. Secondly, this imposes restrictions on the chargers themselves, since try also to find those charges that charge with currents from 100 or even 50 mA. The same “folk” and often recommendedLiitokala Lii-500 can only with 300 mA. Thirdly, many charges capture the moment of full charge by “-dV”, for which, according to the instructions, a current of 0.3 from the capacitance is required.



Another approach says that modern NiMh, damn it, and modern, to charge them 0.3 from the capacitance, 0.5 and even a current equal to the capacitance. In general, in the end, I decided to conduct my own experiment and for 100 cycles Ikea Ladda batteries were charged and discharged in AA and AAA formats with currents of 0.3C, trying to see degradation. It lasted more than six months and the measurement results can be viewed under the cut.

How was the testing


To automate the process, the Opus BT-C3100 charger was used. This memory allows you to work in refresh mode, when the charger runs 3 cycles in a row, as if swaying the battery. It comes in handy when you need to bring new batteries to the tank or shake them for a long time in the nightstand. Well, then I had to checkout.

For the tests, 2 Ikea Ladda AA and AAA batteries were selected. Why Ikea Ladda - because back in the previous text we found out that these are such low-cost analogues of Eneloop Pro with the declared “move” in 500 cycles. So their use is quite reasonable.

Each battery was tagged and charged only in its slot. AAA batteries with a capacity of 900 mAh were charged with currents of 300 mA, AA batteries with a capacity of 2450 mAh were charged with currents of 700 mA. In the resulting table went the discharge values, because We are interested not in how much the battery took, but how much it gave.

The first 30 cycles, the batteries were chased in the refresh mode, then I decided not to leave them unattended and use only one cycle at a time, stacking per day. Actually, because of this decision, testing was delayed.

results


The graphs below show the test results for both pairs of batteries. Blue - sample 1, red - sample 2, yellow dotted line - the average value of the capacitance.



So, you can see how the first few cycles, the batteries, as they are called, reach the capacity. Moreover, the maximum is reached somewhere by the 10th cycle. There, the green dotted line is the payback point of the battery. Those. somewhere around this moment, batteries become more profitable than buying batteries.

Then comes a relatively even location on the “shelf”, moreover, note that the actual battery capacity is higher than stated. I understand that this is a factory stock for degradation.

Well, where is she herself? As you can see, its first signs appear in the least capacious AAA somewhere on the 76th cycle (earlier in one sample, in the second - later, on average, somewhere in the 76th). Moreover, a breakdown of the declared capacity of 900 mAh happens on the 90th cycle. Well, then the degradation begins very explicit.



For AA, the situation is slightly better. Real degradation begins somewhere in the 90th cycle, but the “breakdown” of the declared 2450 mAh is already in the 99th cycle.

findings


Obviously, degradation exists. However, my measurements show that it becomes noticeable closer to 90 cycles. And this is clearly not worth the time to look for charges that can charge with low currents and time spent on long battery charging.

Personally, in my use case, batteries are most often used in children's toys or various sensors. In other words, I’m more likely to lose these batteries than I will see a real drop in capacity. I think that for most readers of this topic the situation will be similar.

Disadvantages of testing and excuses of the author


I immediately wanted to note the testing flaws. Firstly, I used only two samples of each format to level out a possible marriage, or vice versa, the overestimated properties of one of the pair. In theory, it would be necessary to use 3 samples to obtain the average and possible rejection of one of the specimens. But in my chargers there were only 4 slots, and I wanted to test both AA and AAA at a time.

Secondly, I used the Opus BT-C3100 mass charging, which has a number of disadvantages. It is known that the output is different from slot to slot and can go for plus or minus 50-70 mAh. In addition, people complain that charging can recharge batteries and ruin them faster than absolutely correct charges. It was decided to turn the disadvantage into a virtue and a) charge the batteries only in their own slots in order to level the run-up, and average the results b) assume that in the real case people are unlikely to massively use something like SkyRC MC3000 for 6,000 rubles, which means the results of the experiment will be close to the average scenario with a “popular” mass exercise. Well, it was even more interesting when degradation manifested.

Thirdly, there were periodic breaks in testing, such as holidays, business trips, etc. delays that prevent daily measurements. Again, I think that this only added realism to measurements :)

Fourth, the most important thing - according to the mind, it would be necessary to compare three pairs of identical batteries and charge them with currents of 0.1, 0.3 and 0.5 of the capacity. I myself would look at such results, but the labor costs for the study would be unbearable. Well, one would have to buy two identical chargers.

Probably now you can decide on the format (probably better than AAA, because degradation is faster on them) and drive two sets at different currents, superimposing the results on existing ones. But this is another six months.

Addition to the previous topic


The original text “ Charging AA, AAA and other cylindrical and battery ” turned out to be very popular (109 thousand views and 106+), which suggests that the topic is interesting to people. Since its publication, time has passed and something has changed. I decided not to edit the original text, but to mention two changes here - so they are more likely to see them, because it is unlikely that anyone will read the old texts.

First: One of the chargers that I wrote about in the text was the Miboxer C4. From the moment of publication, the Chinese managed to release two revisions in which a) they systematically raised the charge currents b) in the third revision they removed, and in the 4th revision they returned the battery discharge function. Keep this in mind when looking for yourself this exercise. Ali sellers usually write whether there is a discharge in the memory.



Second: the very cool charging ISDT C4 appeared on the market ( sensible review on Mysku). Fans of radio models are well aware of this company and compact charging has also appeared for standard batteries.


(found a beautiful picture on Banggood).

Distinctive features:

  • Compactness. This is achieved due to the cunning arrangement of the batteries. So, 18650 are charged across, which makes the device not very elongated. This is also a drawback, because the 18650 only fits 2 pieces. AAA, alas, also two pieces.
  • Russian interface.
  • Color screen, where displayed charge graphs updated every 2 minutes.
  • The ability to update firmware via USB (here it is, XXI century!)
  • Support for formats: all standard including LiFePO4, plus NiZn and LiHv
  • Charge current: 0.1 - 3A / slot - maximum 25 watts
  • Discharge current 0.1 - 1.5 A / slot - maximum 10 watts

Cons: the price is 3.5..4 thousand rubles. Charts can not be reset to the computer (but it is rather nitpicking). Well, two AAA is somehow not enough.

Askan


If this and the previous article seemed useful to you when choosing batteries and chargers, then I remind you that there is a donation mechanism on Habré. In turn, I undertake to spend it on testing new memory devices and bullying batteries.

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