What does 12000 milliamps per hour mean? Li-Po batteries

Discharge current

Typically, the manufacturer assigns the nominal capacity of a lead-acid battery for long-term (10, 20 or 100 hours) discharges. The battery capacity at such discharges is designated as C 10, C 20 or C 100. We can calculate the current flowing through the load during a 20-hour (for example) discharge - I 20:

I 20 [A] = E 20 [A*hour] / 20[hour]

Does this mean that with a 15-minute (1/4 hour) discharge the current will be equal to E 20 x 4? No, that's not true. With a 15-minute discharge, the capacity of a lead-acid battery is typically just under half its rated capacity. Therefore, the current I 0.25 does not exceed E 20 x 2. That is The discharge current and discharge time of a lead battery are not proportional to each other.

The dependence of the discharge time on the discharge current is close to a power law. In particular, Peukert's formula (law) is widespread - named after the German scientist Peukert. Peukert found that:

I p * T = const

Here p is the Peukert number - an exponent that is constant for a given battery or type of battery. Peukert's formula also applies to modern sealed lead acid batteries.

For lead batteries, the Peukert number usually varies from 1.15 to 1.35. The value of the constant on the right side of the equation can be determined from the nominal capacity of the battery. Then, after several transformations, we obtain a formula for the battery capacity E at an arbitrary discharge current I:

E = E n * (I n / I)p-1

Here E n is the nominal capacity of the battery, and I n is the discharge current at which the nominal capacity is set (usually a 20-hour or 10-hour discharge current).

Final discharge voltage

As the battery discharges, the voltage on the battery drops. When the final discharge voltage is reached, the battery is disconnected. The lower the final discharge voltage, the greater the battery capacity. The battery manufacturer sets the minimum permissible final discharge voltage (it depends on the discharge current). If the battery voltage drops below this value (deep discharge), the battery may fail.

Temperature

When the temperature rises from 20 to 40 degrees Celsius, the capacity of a lead battery increases by about 5%. When the temperature decreases from 20 to 0 degrees Celsius, the battery capacity decreases by approximately 15%. When the temperature decreases by another 20 degrees, the battery capacity drops by another 25%.

Battery wear

The capacity of a lead-acid battery as delivered may be slightly more or slightly less than the nominal capacity. After several discharge-charge cycles or several weeks of being under a “floating” charge (in a buffer), the battery capacity increases. With further use or storage of the battery, the battery capacity decreases - the battery wears out, ages and eventually must be replaced with a new battery. To replace the battery on time, it is better to monitor the battery wear using a modern battery capacity tester -

7. How to check the capacity of a lead-acid battery?

The classic method of checking a battery is a test discharge. The battery is charged and then discharged with a constant current, recording the time to the final discharge voltage. Next, determine the residual capacity of the battery using the formula:

E [A*hour]= I [A] * T [hour]

The discharge current is usually chosen so that the discharge time is approximately 10 or 20 hours (depending on the discharge time for which the nominal battery capacity is indicated). Now you can compare the remaining battery capacity with the nominal capacity. If the residual capacity is less than 70-80% of the nominal capacity, the battery is taken out of service, because with such wear, further aging of the battery will occur very quickly.

The disadvantages of the traditional method of monitoring battery capacity are obvious:

• complexity and labor intensity;
• removing the battery from use for a long period of time.

To quickly test batteries, there are now special devices that allow you to check the battery capacity in a few seconds.

We choose two things in the store that should be used “in tandem,” for example, an iron and a socket, and suddenly we encounter a problem - the “electrical parameters” on the label are indicated in different units.

How to choose instruments and devices that suit each other? How to convert amps to watts?

Related but different

It must be said right away that a direct conversion of units cannot be done, since they represent different quantities.

Watt - indicates power, i.e. the rate at which energy is consumed.

Ampere is a unit of force that indicates the speed of current passing through a specific section.

To ensure trouble-free operation of electrical systems, you can calculate the ratio of amperes and watts at a certain voltage in the electrical network. The latter is measured in volts and can be:

• fixed;
• permanent;
• variables.

Taking this into account, a comparison of indicators is made.

"Fixed" translation

Knowing, in addition to the values ​​of power and strength, also the voltage indicator, you can convert amperes to watts using the following formula:

In this case, P is the power in watts, I is the current in amperes, U is the voltage in volts.

Online calculator

In order to constantly be “in the know,” you can create an “ampere-watt” table for yourself with the most frequently encountered parameters (1A, 6A, 9A, etc.).

Such a “relationship graph” will be reliable for networks with fixed and constant voltage.

"Variable Nuances"

For calculations at alternating voltage, one more value is included in the formula - power factor (PF). Now it looks like this:

An accessible tool such as the online amperes to watts calculator will help make the process of converting units of measurement faster and easier. Don’t forget that if you need to enter a fractional number in a column, do so using a dot and not a comma.

Thus, to the question “1 watt - how many amperes?”, using a calculator you can give the answer - 0.0045. But it will only be valid for a standard voltage of 220V.

Using the calculators and tables available on the Internet, you can not agonize over formulas, but can easily compare different units of measurement.

This will help you select circuit breakers for different loads and not worry about your household appliances and the condition of the electrical wiring.

Ampere - watt table:

	6	12	24	48	64	110	220	380	Volt
5 Watt	0,83	0,42	0,21	0,10	0,08	0,05	0,02	0,01	Ampere
6 Watt	1	0,5	0,25	0,13	0,09	0,05	0,03	0,02	Ampere
7 Watt	1,17	0,58	0,29	0,15	0,11	0,06	0,03	0,02	Ampere
8 Watt	1,33	0,67	0,33	0,17	0,13	0,07	0,04	0,02	Ampere
9 Watt	1,5	0,75	0,38	0,19	0,14	0,08	0,04	0,02	Ampere
10 Watt	1,67	0,83	0,42	0,21	0,16	0,09	0,05	0,03	Ampere
20 Watt	3,33	1,67	0,83	0,42	0,31	0,18	0,09	0,05	Ampere
30 Watt	5,00	2,5	1,25	0,63	0,47	0,27	0,14	0,03	Ampere
40 Watt	6,67	3,33	1,67	0,83	0,63	0,36	0,13	0,11	Ampere
50 Watt	8,33	4,17	2,03	1,04	0,78	0,45	0,23	0,13	Ampere
60 Watt	10,00	5	2,50	1,25	0,94	0,55	0,27	0,16	Ampere
70 Watt	11,67	5,83	2,92	1,46	1,09	0,64	0,32	0,18	Ampere
80 Watt	13,33	6,67	3,33	1,67	1,25	0,73	0,36	0,21	Ampere
90 Watt	15,00	7,50	3,75	1,88	1,41	0,82	0,41	0,24	Ampere
100 Watt	16,67	3,33	4,17	2,08	1,56	,091	0,45	0,26	Ampere
200 Watt	33,33	16,67	8,33	4,17	3,13	1,32	0,91	0,53	Ampere
300 Watt	50,00	25,00	12,50	6,25	4,69	2,73	1,36	0,79	Ampere
400 Watt	66,67	33,33	16,7	8,33	6,25	3,64	1,82	1,05	Ampere
500 Watt	83,33	41,67	20,83	10,4	7,81	4,55	2,27	1,32	Ampere
600 Watt	100,00	50,00	25,00	12,50	9,38	5,45	2,73	1,58	Ampere
700 Watt	116,67	58,33	29,17	14,58	10,94	6,36	3,18	1,84	Ampere
800 Watt	133,33	66,67	33,33	16,67	12,50	7,27	3,64	2,11	Ampere
900 Watt	150,00	75,00	37,50	13,75	14,06	8,18	4,09	2,37	Ampere
1000 Watt	166,67	83,33	41,67	20,33	15,63	9,09	4,55	2,63	Ampere
1100 Watt	183,33	91,67	45,83	22,92	17,19	10,00	5,00	2,89	Ampere
1200 Watt	200	100,00	50,00	25,00	78,75	10,91	5,45	3,16	Ampere
1300 Watt	216,67	108,33	54,2	27,08	20,31	11,82	5,91	3,42	Ampere
1400 Watt	233	116,67	58,33	29,17	21,88	12,73	6,36	3,68	Ampere
1500 Watt	250,00	125,00	62,50	31,25	23,44	13,64	6,82	3,95	Ampere

Amp-hours in a battery: what is it?

The battery life of a mobile phone, a portable tool, or the ability to supply current to the starter when starting a car engine - all this depends on such characteristics of the battery as capacity. It is measured in ampere hours or milliamp hours. By the size of the capacity, you can judge how long the battery will supply electrical energy to a particular device. The time it takes to discharge and charge the battery depends on it. When choosing a battery for a particular device, it is useful to know what this value means in ampere hours. Therefore, today’s material will be devoted to such a characteristic as capacity and its dimensions in ampere-hours.

In general, an ampere hour is a non-system unit of electrical charge. Its main use is to express the capacity of batteries.

One ampere-hour represents the electric charge passing in 1 hour through the cross-section of a conductor when passing a current of 1 ampere. You can find values ​​in milliamp-hours.

As a rule, this designation is used to indicate the capacity of batteries in phones, tablets and other mobile gadgets. Let's look at what ampere-hour means using real examples.

In the photo above you can see the capacity designation in ampere hours. This is a 62 Ah car battery. What does this tell us? From this value we can find out the current strength with which the battery can be uniformly discharged to the final voltage. For a car battery, the final voltage is 10.8 volts. Standard discharge cycles typically last 10 or 20 hours.

Based on the above, 62 Ah tells us that this battery is capable of delivering a current of 3.1 amperes for 20 hours. In this case, the voltage at the battery terminals will not drop below 10.8 volts.

In the photo above, the laptop battery capacity is highlighted in red – 4.3 ampere-hours. Although with such values ​​the value is usually expressed as 4300 milliamp-hour (mAh).

It should also be added that the system unit of electric charge is the coulomb. The pendant is related to ampere hours as follows. One coulomb per second is equal to 1 ampere. Therefore, if you convert seconds to hours, it turns out that 1 ampere-hour is equal to 3600 coulombs.

How are the battery capacity (amp-hour) and its energy (watt-hour) related?

Many manufacturers do not indicate the capacity in ampere-hours on their batteries, but instead indicate the stored energy in watt-hours. Such an example is shown in the photo below. This is a Samsung Galaxy Nexus smartphone battery.

I apologize for the photo with small print. The stored energy is 6.48 watt-hours. The stored energy can be calculated using the following formula:
1 watt hour = 1 volt * 1 ampere hour.

Then for the Galaxy Nexus battery we get:

6.48 watt-hours / 3.7 volts = 1.75 amp-hours or 1750 milliamp-hours.

What other types of battery capacity are there?

There is such a thing as the energy capacity of a battery. It shows the ability of the battery to discharge within a certain time interval with constant power. The time interval in the case of automobile batteries is usually set to 15 minutes. Energy capacity initially began to be measured in North America, but then battery manufacturers in other countries joined in. Its value can be obtained in ampere-hours using the following formula:

E (Ah) = W (W/el) / 4, where

E – energy capacity in ampere-hours;

W – power at 15 minute discharge.

There is another variety that came to us from the USA, this is a reserve tank. It shows the ability of the battery to power the onboard moving vehicle when the generator is not working. Simply put, you can find out how long the battery will allow you to drive your car if the alternator fails. You can calculate this value in ampere hours using the formula:

E (amp hours) = T (minutes) / 2.

Here we can also add that when batteries are connected in parallel, their capacity is summed up. When connected in series, the capacitance value does not change.

How do you know how many amp hours your battery actually has?

Let's look at the process of checking capacity using an example. But such a controlled discharge can be done for any battery. Only the measured values ​​will differ.

In order to check the actual amp hours of your battery, you need to fully charge it. Check the degree of charge by density. A fully charged battery should have an electrolyte density of 1.27─1.29 g/cm 3 . Then you need to assemble the circuit shown in the following figure.

You need to find out what discharge mode your battery capacity is specified for (10 or 20 hours). And discharge the battery with a current intensity calculated using the formula below.

I = E/T, where

E – nominal battery capacity,

T – 10 or 20 hours.

This process requires constant monitoring of the voltage at the battery terminals. As soon as the voltage drops to 10.8 volts (1.8 on the bank), the discharge must be stopped. The time it takes for the battery to discharge is multiplied by the discharge current. This gives the actual battery capacity in ampere-hours.

If you do not have a resistor, you can use car light bulbs (12 volts) of suitable capacity. You select the power of the light bulb depending on what discharge current you need. That is, if you need a discharge current of 2 amperes, then the power will be 12 volts multiplied by 2 amperes. Total 24 watts.

Important! After the battery is discharged, immediately charge it so that it does not remain in such a discharged state. For such a discharge it is better not to do it at all. With such a deep discharge, they may lose part of their capacity.

The most important parameter of almost any battery is its capacity! After all, it determines how much energy he will give over a certain time. And this is not necessarily a car battery; all batteries, from “finger-type” batteries that you insert into your camera or player, to cell phones, have this parameter. In general, knowing and correctly understanding this parameter is very important! Especially for a car, because if you take the wrong container, you may have problems starting the engine in cold weather, and it may simply not be enough for your on-board network. In general, we'll figure it out...

Let's start with a definition.

Battery capacity - this is the amount of energy that a battery can supply, at a certain voltage, in a certain period of time (often an ordinary hour is taken). Measured in Amperes or Milliamps per hour.

Based on this characteristic, you choose a battery for your car, because often the manufacturer recommends one or another value for the normal functioning of the car. If you lower this parameter, then most likely cold starts will be complicated.

How is the battery capacity determined?

ON many car batteries (and on simple household ones too), we often see this parameter - 55, 60, 75 Am*h (English Ah).

On regular telephones - 700, 1000, 1500, 2000 mAh (thousandths of an Ampere). This parameter just indicates the battery capacity. It should not be confused with another parameter such as voltage, as we know - 12.7V

SO - what do these 60 Am*h mean ( Ah)?

Everything is very simple - this abbreviation tells us that the battery can work for an entire hour with a load of 60 Amps and a nominal voltage of 12.7V. This is the capacity, that is, it is able to accumulate such a reserve of energy.

However, these are maximum values, 60 Amps is a very high current, if you convert it to Watts, it turns out - 60 X 12.7 = 762 Watts. It is enough to warm up an electric kettle several times, or illuminate the whole house for several days, provided that you have LED lamps, which often take only 3 - 5 Watts per hour.

I hope this is clear, I immediately want to say that if the load is not 60 Amps, but say 30, then the battery will work for two hours, if 15 - 4 hours, if 7.5 - 8 hours. I think this is understandable.

But why do some cars have a capacity of 45 Amps, others have 60, and still others should be equipped with 75A options?

All cars are different, they exist as class “A”, the smallest, up to, say, class “E” or “D” - executive sedans. The characteristics of the machines are different, from start-up to subsequent consumption by the on-board network. After all, engine sizes will vary significantly.

So for small and “light” compact cars, a battery of 40 – 45 Ampere-hour is enough, but for large and powerful sedans you need 60 – 75 Ampere-hour.

But why is that?

It's all about - the larger the battery, the more lead, electrolyte, etc. it contains. This allows you to accumulate more energy and release more of it at once. So let's say in the 40A version the starting current will be about 200 - 250A, which it can deliver for 10 seconds - for a small engine, this is enough, say, up to a volume of 1.0 - 1.2 liters. But this may not be enough for large engines of 2.0 - 3.5 liters; here the starting current should be 300 - 400A, which is twice as much. It is also worth considering that winter starting is even more difficult - you need to turn not only the pistons, but also thick engine oil.

Therefore, you can install large batteries on small cars, but small ones on large cars are undesirable.

Housing and capacity

The capacity directly depends on the amount – and electrolyte – in the design. It is clear that the more of these materials are used, the more energy the battery can store. That is why the 40 and 75A options will differ almost twice, both in size and weight. That is, there is a directly proportional dependence here.

Subcompact cars are small cars themselves, their engine compartment space is scanty, and therefore installing a “huge” battery is simply not rational! And why? If the small version does a great job, it starts the engine.

Capacity drop

Over time, the battery degrades, that is, the capacity begins to drop. For conventional acid batteries, the service life is approximately 3–5 years (there are, of course, exceptions, they last 7 years, but this is rare).

The capacity drops, and the battery can no longer deliver the required starting current, say 200 - 300A in 10 seconds. Accordingly, the time comes to change it. But why the process of degradation occurs, there are a lot of reasons:

• Sulfation of plus plates. During deep discharges, a coating of sulfuric acid salts forms on the plates; it is very dense and completely covers the surface. The contact patch with the electrolyte decreases and the battery capacity decreases.
• Shedding of plates. This can happen during overcharging, especially when the electrolyte level in the bank is not enough. The plates simply fall down and the capacity decreases, sometimes simply catastrophically.
• Bank closure. If the plates bridge each other, positive and negative, the bank will fail. Not only the capacity will drop, but also the voltage. However, like this.

Now let's watch a useful video.

This is where I end, I think the information was useful to you. Read our AUTOBLOG.

As often happens in our imperfect world, the generally accepted unit for measuring battery capacity has become a unit that cannot accurately reflect the capacity - milliamp-hours (mAh, mAh, mAh). Many manufacturers have tried to “instill” in the population the “correct” unit of measurement - watt-hours (Wh, Wh, Wh), but for some reason it has not yet taken root.

Let me explain why watt-hours are the “correct unit” and milliamp-hours (or ampere-hours) are the “wrong” ones. Batteries and battery assemblies come in different nominal voltages, for example 1.2, 3.6, 3.7, 7.4, 11.1, 14.8 V. However, a 7.4 V 2000 mAh battery has twice the capacity of a 3.7 V 2000 mAh, with watt-hours of such confusion it won’t - the first battery has a capacity of 14.8 Wh, the second 7.4 Wh. In this case, to get the watt-hours, I simply multiplied the rated voltage of the battery by the charge in ampere-hours (1Ah=1000mAh).

But that is not all. Let's see how the Li-ion battery from the Cubot S200 smartphone discharges.

During the discharge process, the voltage on the battery changes. For our lithium-ion battery it drops from 4.291 V to 3.0 V.

At the same time, the battery characteristics indicate an average voltage of 3.7 V and a charge in milliamp-hours for this voltage. The real amount of energy that the battery will produce can only be calculated in watt-hours by multiplying the current voltage by the current current at each time and obtaining the final capacity value from the sum of these values, dividing it by the number of such calculations per hour.

The analyzer discharged the battery in 36694 seconds, maintaining a constant discharge current of 301 mA. If we simply multiply 301 by 36694 and divide by 3600 (the number of seconds in an hour) we get 3068 mAh. Let's multiply this value by the nominal battery voltage of 3.7 V and divide by 1000. We get 11.35 Wh.

But what really?

The analyzer measures voltage values ​​10 times per second. By multiplying each voltage value by the discharge current, we obtain the power during each measurement. Let's add up the power values ​​of all 366,913 measurements and divide by the number of measurements per hour (36,000).

With your permission, I will not provide screenshots of 366893 intermediate lines. :)

The resulting value is 11.78 Wh - the real amount of energy that the battery provided. If we divide this value by 3.7V we get a calculated charge of 3184 mAh.

The discrepancy between the actual amount of energy supplied by the battery differs from the calculated one by 3.8%; this is exactly the error that will result if you measure not watt-hours, but milliamp-hours produced by the battery.

In fairness, it must be said that for conventional batteries this discrepancy is usually about one percent.

That is why all devices that measure battery capacity in milliamp-hours give only approximate results, because the voltage changes during the discharge process, and this is not taken into account.

Accurate results can only be given in watt-hours, provided that many measurements are taken during the discharge process.