An Observation about Modern Lithium-Ion Batteries

I have visited this subject before, but feel that I should post about it again.

The way Lithium-Ion batteries first became popular, they either had metallic lithium, or graphite as their negative electrode, and lithium-cobalt-oxide as their positive electrode. This stored much energy, but also presented an initial cause for alarm, especially since some of the then-new batteries were prone to catch fire, when over-charged. In response, there existed a trend followed by some companies and manufacturers, to switch to lithium-manganese-oxide, either in the layered or the spinel form, as the next-best positive electrode.

It would seem that the lithium-cobalt-oxide batteries produce 4.2V when fully charged, while the lithium-manganese-oxide batteries only produce 3.7V when fully charged ( :1 ) , and the latter battery-type was deemed ‘safer’.

Additionally, there exists a battery-type which has lithium-iron-phosphate, which is even safer than the 3.7V batteries, and which only produces 3.4V when fully charged. This third family of batteries isn’t used in household appliances, but is used in Segways and some electric cars, where it would be exceptionally unfortunate if the batteries could explode, simply due to a traffic accident – a hypothetical collision.

What seems to have happened – and I don’t have proof – would be called a ‘trend reversal’. Some manufacturers have switched back to using the lithium-cobalt-oxide batteries, simply because those store more energy.

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Why do consumers need to know this? So that they don’t place 3.7V batteries – which are labeled identically to the other type – into 4.2V chargers, and leave them there. That’s all.

I suppose that a valid question which some readers might have would be, ‘What has become of the safety / over-charging issue?’ And my answer would be that most of today’s charging circuits have become ‘smarter’, and less prone actually to over-charging the batteries. The best example of this is the smart-phone. However, if some people buy separate batteries for ‘Vapers’, then those devices have a reputation of ‘no charging intelligence’, i.e., of sometimes over-charging the battery.

The typical behavior of a dumb charger is, to ‘Apply a constant voltage of 4.2V, and when the current which the battery draws falls below a certain amount of current, give an indication that the battery is fully charged. But keep applying 4.2V, even after the LED has changed color.’ The lithium-manganese-oxide batteries will also tolerate such charging voltages for brief periods of time. And the lithium-cobalt-oxide batteries will realize their maximum held charge that way.

The thing not to do, is to keep whichever batteries in their dumb charger for long periods of time, after the LED indicates they are charged.

I also want to add, that this posting is meant to voice an issue, with the low-budget lithium-ion batteries, in the modern era. I understand that high-budget, big-ticket items exist, such as…

(Updated 10/19/2018, 6h10 … )

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Measurement of 18650 Batteries and Conclusion

I have now received my “9900mAh, 3.7V” batteries, and their bundled “4.2V” charger, which I first wrote about in this earlier posting. After receiving a full charge, their measured voltage while still inserted was 4.215V , immediately after removed at no load 4.195V , and after standing for 30 minutes, at no load, 4.138V . When new they require approximately 4h + 5min to charge.

I have to conclude that these batteries do not contain any series-connected, internal, over-voltage-protection chip. They seem to be based on the Layered Lithium-Manganese-Oxide:┬áLi2MnO3 . They differ from the “3400mAh, 3.7V” variety, in that the other kind are based on the Spinel Lithium-Manganese-Oxide: LiMn2O4 .

I must only use this charger, with the batteries it shipped with.

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Why we see voltage inconsistencies, with Li-Ion Batteries

I use lithium-ion batteries, which I abbreviate to Li-Ion, the same way other people use them. But I have noticed that the fully-charged voltage of each one is not the same.

There is a WiKiPedia article, which explains well enough for my needs, how Lithium-Ion batteries work. One question which I had not previously had an answer to, was, ‘If I was to design a Lithium-Metal battery, aside from using Lithium as the anode, what material would I use as a cathode – as the oxidizer?’ And the above answer provides possible solutions.

One fact which I have noted before, is that I have ordered a battery charger from Ebay, for ‘Type 18650′ batteries, and that these batteries usually have a fully-charged voltage of 3.7 Volts, and that some compatible batteries only hold 3400mAh of charge, while others hold 9000mAh of charge.

Well, when the battery in my phone has a voltage of about 3.7V, it is only indicated as 60% charged. At 90% charged, my phone battery has 4.1V, and a typical charging-cycle will bring it up to 4.2V – enough to fry certain other batteries.

All of these observations could well be explained, by the phone battery being a Lithium-Cobalt-Oxide battery, while certain other, exchangeable batteries may simply be Lithium-Iron-Phosphate batteries, or yet other batteries. ‘Other exchangeable batteries’ could include the ones in my camera, etc.. The fact that the cathode can have different compositions, will lead to different voltages.

But, when I do receive the batteries and charger I ordered, which are supposed to have a 9000mAh capacity, I will need to verify something. The Type 18650 batteries need to have a fully-charged voltage of 3.7V . Yet, there seem to be high-capacity batteries which hold more charge than merely 3400mAh.

There is a possible, little trick which the makers of my battery and charger could be using. They could have programmed their charger, only to charge the batteries to 3.7V – as usual. But the high-capacity batteries there, too, could be of the Lithium-Cobalt-Oxide type, which can theoretically be charged to 4.2V. At 3.7V, that charger could simply stop charging them.

When I have received my charger and the batteries, what I will have to do after charging those, will be to measure their voltage. The reason for this will be the fact that other battery-types are only allowed to be charged to 3.7V . I will need to know whether it would be safe to insert a Lithium-Iron-Phosphate battery into the charger, instead of the higher-capacity batteries it ships with.

(Edit 12/11/2016 : Additionally, I will want to measure the voltage of the same battery, 30 minutes after taking it out of the charger, without having connected any load to it. I could expect, to see a voltage of 4.2V , and then one of 4.1V . This would tell me that the same charger cannot be used with the lower-capacity batteries. But all of this thinking is pure guesswork, until I have measured the battery. I am insinuating that the batteries are mislabeled as 3.7V batteries, and as soon as something is mislabeled, we need to measure values. )

If the yet-to-arrive batteries test out as having 3.7 V or close to it, I will also know that I can trust the charger I ordered, with the lower-capacity battery-type, which it does not ship with.

Dirk

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Recent Disappointment in Ebay, New Battery-Type

It has been some time since I bought anything on Ebay. But as it happens, I used to carry an LED flashlight with me, the main purpose of which was to prevent me from misplacing my key-chain, and it has since stopped functioning. And so a natural thing I would want to do, was buy a new replacement-flashlight, and because this is a low-priority purchase – for the device actually to work – a good place to do so would be, Ebay. This may take some time to deliver to me.

(Last Edited 11/26/2016 . )

But when I did my searches on Ebay today for such a simple item, certain aspects of the results disappointed me. Specifically, I think it was the lack of English skills on the part of the sellers. It seems that the trend on Ebay now is, to put many identifiers into the one-line item description, and to have that pass as its full description, when often, a list of identifying keywords as such, can be incomprehensible to the reader, if 2 or 3 of the identifiers are not known to him.

Where a full item description was supposed to exist, many Ebay items today have nothing.

One of the identifiers which frustrated me today, was what the battery requirements of the new flashlights are. They are: “18650”.

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