Why is the value of electric current not included on the battery?

Question

What is the reason for this? The fact that it is a value that changes when modifying electrical circuits and, unlike voltage, we can not explicitly define it? I make my considerations with direct current.

goldi74 · Answer

Current depends on the resistance of the circuit. The battery itself does not produce current only voltage. Current begins to flow only when the battery is loaded with a load.

SciTuber · Answer

I understand that as the voltage on the battery is specified equal to 3V, while the current is not necessarily, this is because it can take different values? I was prompted to these considerations by the fact that when the nth receiver is connected to a series circuit, the voltage of the source will not change, while in the case of a parallel circuit, the current source intensity will increase....

goldi74 · Answer

Read about Ohm's law.

SciTuber · Answer

I will read. I will take this opportunity to ask one more question. When the nth receiver is connected to a series circuit, according to the rule, will the intensity of the source not change, while the voltage and intensity of the receivers will decrease in direct proportion?

Falco76 · Answer

On a 3V battery there is no such data, but take a battery and there you will find: voltage V, Ah capacity, and inrush current - this is the current of discharge of the battery under certain conditions, specified by the manufacturer. The current that will flow in the circuit depends on the resistance of the circuit - as a colleague wrote earlier.

Added after 4 [minutes]:

Are you asking about the current source or voltage source, or what happens in practice?

Krzysztof Kamienski · Answer

For the total circuit.

tomekm33 · Answer

Read, maybe something will brighten up for you: "Ohm's Law"

There is a voltage on an unloaded battery because.... Voltage is the potential difference, in this case between the two terminals of a battery (actually a cell, but that's a detail). We associate current with flow. If the poles are not loaded or otherwise connected to each other then current does not flow.

Artur k. · Answer

The question is not at all as silly as it might seem. While it indeed makes no sense at all to state the current on disposable cells/batteries, there would be nothing wrong if manufacturers stated the capacity of a new cell as they do in rechargeable batteries. Such information would give some idea of what to expect from such a cell.

tomekm33 · Answer

Arthur k. what's right is right, although it is possible to find such information - here is an example . The manufacturer has stated a capacity of 1200 mAh. Ba! There is even datasheet Only that... First - not everyone needs such detailed information (datasheet). After 2 - it would be better if (as you mentioned) at least approximate capacity in mAh was given. After 3 - you probably won't find information for every cell.

Artur k. · Answer

Of course, after all, it would be enough to give, for example, the average capacity on the cell. In most cases, such information is sufficient, and if someone wants to know the details, let him look for a datasheet. Well, unfortunately, Varta is one of the few manufacturers that provide such information (and even this is not for every cell). Most don't, and the datasheet is sometimes not easy to get to at all.

398216 Usunięty · Answer

The trouble with this is that the capacity of the battery is closely related to the current that is drawn from it.
My opinion is that this data is intentionally not available to "mere mortals", because they could misinterpret it and then there would be more trouble than it's worth. Besides - in 90% of cases a given battery model is dedicated to a certain type of receiver - we are talking, of course, about "factory" designs - and for such a receiver it performs properly. Admittedly, it is possible to use an alkaline cell instead of carbon cells (there are still such manufactured) - but for the user it is only better - the equipment will last longer. So the user himself has a choice - whether the cell "usual" and frequent replacement, or alkaline with much higher efficiency and capacity, so replaced less often but more expensively.
I don't know how it is nowadays, but, for example, in Polish (portable) radios, the recommended type of battery was given - and I even remember that I saw in some manual "estimated operating time" on the recommended cells (which, in total, gave nothing anyway, because at that time there were only batteries of one type available - lousy and pouring....

).
I think I still have somewhere a flash (Polish) where the number of flashes on a set of carbon batteries and in comparison - on alkaline batteries was given. On the Polish batteries, these figures did not coincide with reality, because the batteries lasted at most for a few shots....

Artur k. · Answer

Of course, except that the identical situation is with batteries, and on batteries the capacity is given. In my opinion, this does not change anything, and even makes it more difficult - for example, to compare different cells, especially cells from different manufacturers. With this I will not agree, this may have been the case in the past, but not today. Today anyway, most devices are powered by AA or AAA type cells. Even in multimeters where practically from time immemorial reigned 6F22 today already meet AAA precisely because of their incomparably higher capacity than 6F22. There used to be no readily available, cheap and good step-up converter circuits, and assembling a 9V from AAA cells would significantly increase the weight and size of the instrument. Today there is no problem with this, which is why this type of battery is slowly dying out.The same way the once very popular 3R12 battery - the so-called flat battery, which was dedicated mainly to flashlights - died out. In the past, when, first of all, there was no such variety of cells, there was no point in stating the capacity. However, today I believe that such information would be needed by many people.

RitterX · Answer

@SciTuber A cell (battery of cells) has a certain internal resistance, which changes with discharge. This is how a cell differs from an ideal voltage source. If you lick the theory a bit, you will learn that an ideal voltage source has zero internal resistance. Because of the existence of internal resistance in a real cell as well as a generator, when you connect the poles to each other with a conductor of negligibly small resistance, an infinitely large current will not flow. It will be limited by the sum of the resistance of the conductor shorting the poles and the internal resistance of the cell. For this reason, the actual cell, when short-circuited, will heat up and in extreme cases may even catch fire and explode. For a typical application, the internal resistance should be taken into account in the calculations, because under load the voltage of the cell will not be equal to its SEM, but reduced by the drop on the internal resistance, which is proportional to the current drawn from the cell. As mentioned above by colleagues, in the catalog notes you can find much more information on the permissible and recommended current drawn from the cell. In batteries the capacity is given for two reasons. First, to be able to estimate the maximum amount of energy stored in them and second, depending on the design of the battery, to determine, approximately, the typical parameters of the charging current.

398216 Usunięty · Answer

I think that in the case of car batteries this is necessary - after all, the car manufacturer equips its products with a specific type (capacity, starting current and even size, but that's another matter) of battery - precisely because of the energy requirements of a particular vehicle. As for batteries - the case is similar - if the manufacturer has decided that they are to be AA then you will not put AAA, because it will not contact. And vice versa - You won't put AA in the place provided for AAA because it won't go in. Comparing a bunch of batteries of a given type with each other, you can see quite significant differences in capacity from one type to another - so in some way this is also an indication of the current appetite of a given device. Of course - old equipment was adapted to the batteries of the time - it is known that those 10 and even more so 20 years ago batteries of the same type as those produced today were of much lower capacity.Example: The first electric (battery) alarm clock I bought for myself (I like to sleep...) was adapted for a R-14 battery. Today, at the market you can easily buy a similar one for a AAA battery. The working time of my first alarm clock is a month at the most, and the one from the bazaar - a Chinese one for a modern AAA battery - two - three times as much (with a daily wake-up call). So it's not only the device itself (its current-consuming capacity) that affects the working time, but also the quality of the battery; since the many times smaller AAA present-day can be thus compared to type C.

kortyleski · Answer

Even if the capacity of batteries was stated, marketers would immediately come up with thousands of ways to measure so that the batteries of a particular manufacturer would be the best. It would be necessary to standardize the measurement from the top down and this will not work on the free market.

Artur k. · Answer

But rechargeable batteries are not only in cars. After all, there are rechargeable batteries in typical AA and AAA and other sizes. Here, too, the capacity is given, and it varies greatly. And that's for sure, except that the possible stretching would be relatively easy to catch by a thinking person. It's exactly the same with rechargeable batteries - it's been known for a long time that in the case of, for example, AA-size NiMH, it's rather rare to find batteries with capacities greater than 2500mAh (typically around 2000-2300mAh, although I once had a Sanyo 2700mAh), if someone quotes a much higher capacity than everyone else then you can immediately sense that something is wrong. The problem is different - while in the case of a rechargeable battery it is quite easy to check what capacity it has and possibly prove that it does not hold the declared parameters, an alkaline cell is disposable - once you discharge it to check the capacity, the physical evidence ceases to exist.

CMS · Answer

And this very fact, I believe, is the main reason why, on batteries we have only voltage. And that the batteries from the bunny, or those that used to have such a funny bar to check the level of charge, last much longer than NONAME's or other market batteries, is no news. And anyway, the capacity of rechargeable batteries is not everything. For example, my dad's old camera, some Soniak with a 5MPx sensor, on branded 2200mAh batteries (probably Sanyo, but I won't give my head) after literally a few photos sucked the cells to zero. I purchased some industrial cells (whatever that was supposed to mean) of an unknown brand, with a capacity of 2200mAh, on the volume, and you can easily snap out a 512MB card and still rip it to the computer. Here's where the Eneloops came from.... And other serious rechargeable batteries Greetings. CMS

Artur k. · Answer

Eee, I think the real reasons are different. What would be wrong if manufacturers quoted the average capacity of a cell of a given type? I'm far from conspiracy theories, but from my observations it seems that some people could realistically lose out on this.Do a simple test - buy one AA battery each from, say, 3 different manufacturers - let it be Energizer, Duracell and some cheap ones such as Carrfeour. Measure the short-circuit current of each of them, put it together with the price per unit and draw your conclusions. The Eneloops are about something else - Eneloops and all the new generation have a much smaller capacity than classic NiMH, for that they have a completely different property - much less spontaneous charge loss. That's what this is all about. .

jarek_lnx · Answer

Batteries that have a datasheet with specified capacity and internal resistance, as well as discharge characteristics, are offered by many manufacturers. Batteries with datasheets are a separate product line, they usually have "industrial" in the name, an ordinary user who buys batteries in a nearby market is unlikely to get the "industrial" version, but only a regular one, and must be satisfied with the assurances of marketers that they are simply the best.

I used to do tests and remember that batteries with the highest capacity do not have the lowest internal resistances.

Artur k. · Answer

And it depends what nearby store. Not long ago, there were Varta Industrials in a kiosk near me. Interestingly, they were not at all expensive - I think they were 2zl each for AA.

Zygmunt_mt · Answer

I, for many(maybe decades) years, check the condition of the battery, by briefly measuring the short circuit current. For such a dictum once, I had my post deleted to the trash. And I continue to measure, because I know what, and why, I am doing. As written by Colleagues RitterX and Arthur K , The magnitude of the short circuit current, indicates the internal resistance of the cell(battery). And it is one of the most important parameters, indicating the amount of stored energy. Of course, it must be done with specific and preferably, the same wires, supplying the meter. They can also be Chinese, (these have a resistance, even tens of milliohms) and the instrument then less, loads the cell. It is important that the measurement is very short, so that only the readings, relatively stabilized. Even for used NiMh and NiCd (not Lion ) rechargeable batteries I use this.

CMS · Answer

I always did the measurement of Rw (for 18650 cells) on the principle, measuring the voltage of a charged cell "at idle", then measuring the voltage of this cell with a "plugged in" resistor 10Ω 5W, (but I recommend a larger power, because you can burn your fingers), after 5s. after connection. Then I calculated from the formula:
RW=R(U without load ÷ U under load).
Till now it worked, but maybe there are better ways.

Greetings.
CMS

Zygmunt_mt · Answer

Well, yes. It certainly gave you a picture to compare the internal resistance, but not the resistance itself in Ω (ohms), directly. Well, because what is according to your way of reasoning RxU. It is Ohm or V/A(ohm) multiplied by V(volt) ? So even if only by looking at the units, right ?

Artur k. · Answer

Not exactly, the value of the short-circuit current, yes it indicates the internal resistance of the cell, but it does not indicate the amount of energy that such a cell can store. It is perfectly evident by looking at the characteristics of small batteries. Those with the highest capacities do not necessarily have the highest discharge current. And, after all, the discharge current depends on the internal resistance.In fact, one of the colleagues has already mentioned this: .

Anonymous · Answer

Because also the measurement of Rw makes sense but with the current I with which we intend to load (operate) this battery. That is, using a resistor with a value of R=U/I.
Measuring the short-circuit current is actually measuring the current with a load of 0.1 Ohms - that is, a current far greater than the current of ordinary operation, which calls into question the advisability of such a measurement, in addition, it is usually not healthy for the battery.

Artur k. · Answer

Makes sense, I have long checked the overall condition of cells in this way. Very often we are not able to check a cell by loading it with the nominal current at which it operates in the device, because we simply do not know the value. Measuring the voltage without a load also very often gives very little. I know from experience that a new fully operational alkaline AA cell from a reputable manufacturer has a short-circuit current of about 8-9A, while the SEM of the cell is usually about 1.55V. In contrast, a cell that has already worked a little will have about 5-6A while the SEM is around 1.5V - so measuring the SEM does not arouse suspicion, while measuring the current indicates that the cell has already worked a little. In contrast, cells having a short-circuit current of about 2-3A often have a SEM around 1.4V. SEM begins to drop dramatically only at the end of the cell's life, when the short-circuit current itself is already very low. Often the current of 1-1.5A have cells with SEM of about 1.3V, while such cells already practically exhausted with SEM of about 1.1V can still give 500-700mA on a short circuit. SEM does not depend linearly on the state of charge of the cell, hence a better method of checking the cells is to measure the short circuit current (provided that we know what values to expect). Of course, this is not healthy for the cell, but if such a measurement lasts for a very short time, its effect on the cell is negligible. In field conditions, we have no other way to check the state of the cell than by measuring the short circuit current. This is because no one carries with them an array of high-power resistors to check the cells. For this universal meter we usually have with us (or at least I have). Many times in this way I have also caught brand new, damaged cells - SEM within 1.55V, while the short circuit current barely 1A. I put brand-new cells into the device, and the device does not work, I measure the voltage - it is ok. Well, and what can you think to yourself at this point? Also, as you can see, the purpose and sense is there, only that you can not do it mindlessly - you need to know what to expect. Then such a measurement can provide a lot of information.

Zygmunt_mt · Answer

Not exactly, the value of the short-circuit current yes indicates the internal resistance of the cell, but does not at all indicate the amount of energy that such a cell can store. I was mainly concerned with this equation, in which Om =Om multiplied by volts. And this stings and will sting my eyes. It's just that the so-called titers or units don't agree, and they should or even must. And capacity depends on many things, maybe even less electrical and more chemical and physical(dimensions). And with your post of 19:52, I agree completely. Greetings

Why is the value of electric current not included on the battery?

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