# Battery

Battery is the primary source of any gadgets such as electronics, wireless, smartphone, laptop, clock or remote etc. Are you able to imagine things without these energy sources? We wouldn’t be able to build any wireless device and need to believe wired power source only, even electric cars and space missions wouldn’t be possible without Batteries. Today during this tutorial we discuss briefly about various sorts of batteries, their classification, terminology and specifications.

Let’s see the essential difference between A battery and a cell. Also let’s determine why we exactly need A battery and why can’t we use the Alternating power (i.e., AC power from the wall sockets) rather than DC power.

## Cell

A cell is an energy source which may deliver only DC voltage and current which are in very small quantities. for instance if we take cells that we use in watches or remote controls, it can give maximum of 1.5 – 3V.

## Battery

The functionality of the battery is strictly same as that of a cell but A battery may be a pack of cells arranged may be a series/parallel fashion in order that the voltage are often raised to desired levels. the simplest known example for A battery may be a power bank which is employed to agitate smart phones. If we ever see the within of an influence bank we will find set of batteries arranged serially/parallel supported the need . Batteries are arranged serial to extend the voltage and in parallel to extend the present.

Now Why DC is preferred over AC? In most of the portable electronics, AC can’t be stored where as DC are often stored with none difficulty. Even the losses thanks to AC power are more in comparison to the DC power. that’s the rationale DC is preferred for portable electronic devices.

## Technical terms used while handling batteries

We can’t just keep it up using voltage and current alone to elucidate a few battery’s functionality, there are some unique terms that defines the characteristics of A battery like Watt-hour (mAh), C-rating, nominal voltage, charging voltage, charging current, discharging current, stop voltage, time period , cycle life are the few terms wont to define a batteries performance.
Let’s discuss each of the term briefly,

### Power Capacity

It is the energy stored during a battery which is measured in Watt-hour
Watt-hour = V * I * hours {since voltage is kept constant, so it’s measured in Ah/mAh}

We generally see the battery ratings as 2500 mAh or 4000 mAh while reading the specifications of a sensible phone. What does that mean?? Let’s see

Example: 2500 mAh it means the battery features a capability to deliver 2.5A/2500mA of current to the load for 1 hour. The time that the battery works continuously depends upon the load current that it consumes. So if the load consumes only 25 mA of current then the battery can stay alive for 100 hours. How is it?

25 mA * 100 hours {so 25 mA of current for 100 hours}

Similarly 250 mA for 10 hours So on.

Though the theoretical calculations seem ideal but the battery’s duration changes supported the temperature and therefore the current consumption etc

### Power capability

It means the quantity of current that the battery can deliver. it’s also referred to as C-rating.
Theoretically, it’s calculated as A-h divided by 1 hour.

We are going to consider such a battery. Which has a power backup of 10000 mAh.
After dividing 10000 mA hour/1 hour gives 10000 mA = 10 A = 10 C
So, A battery with 10000 mAh of capacity will have a C rating of 10 C which suggests the battery features a capability of delivering 10 A of current at a continuing voltage (fixed voltage/rated voltage).
If A battery has 1C rating then the battery features a capability of delivering 1A of current.
Note: Higher the C rating, more the present which will be drawn from the battery.

### Nominal voltage

While defining power capacity we’ve a unit called Wh which may be elaborated as V * I * hour but where did the voltage gone? because the voltage of the battery are going to be constant and can not be varied, it’s considered as nominal voltage (fixed voltage). So since the voltage is fixed only Ampere and hour are considered because the unit (Ah/mAh).

### Charging current

It is the utmost current which will be applied to charge the battery i.e., practically maximum of 1A/2A are often applied if A battery protecting circuit is in-built but still 500 mA is that the best the range for charging the battery.

### Charging voltage

It is the utmost voltage that ought to be applied to the battery to efficiently charge A battery . Basically 4.2 V is that the best/standard charging voltage. When the battery is given 5 V current. So he accepts only 4.2 V current.

### Discharging current

It is the current that can be drawn from the battery and is delivered to the load. If the current drawn by the load is greater than the rated discharging current, the battery drains very fast which causes the battery heat up quickly which also causes the battery to explode. So it is cautious to determine the amount of current drawn by the load as well as the maximum discharging current a battery can withhold.

### Shelf life

There might be a situation where the batteries are kept idle/sealed especially in the stores/shops for a long period of time. So shelf life defines the time period a battery can be stay powered up and should be able to use it for a rated time period. Shelf life is especially considered for non-rechargeable batteries because those are of use and throw. For rechargeable batteries albeit the shelf time is a smaller amount , we will still recharge it.

### Cut-off voltage

It is the voltage at which the battery can be considered as fully discharged, after which if we still try to discharge from it the battery gets damaged. So beyond the cut-off voltage the battery should be disconnected from the circuit and should be charged appropriately.

### Cycle life

Let’s consider a battery is fully charged and it is discharged to 80% of its actual capacity, then the battery is said to be completed one cycle. Likewise the number of such cycles that a battery can charge and discharge defines the cycle life. The more the cycle life the better will be the battery’s quality. But if a battery is discharged to say 40% of its actual capacity considering the battery is fully charged initially, it cannot be considered as a cycle life.

### Power density

It defines the battery power or capacity for a single mass. Such as 100 Wh / Kg (alkaline battery standard power density) means that it provides a power capacity of 100 Wh for a 1 kg chemical composition.
Now, volume of a AAA alkaline battery is 11.5 grams. So if 1Kg can give 100 Wh capacity, then what proportion a 11.5 gram AAA batery can give?? Let’s calculate.
Wh (for 11.5 gm) = 100*11.5/1000 = 1.15 Wh

So, we know the nominal voltage of alkaline battery is 1.5V. So it provides 1.5V * (1.15/1.5)A * 1 hour gives 0.76 Ah = 760 mAh of power capacity which is almost equal to the power capacity of a standard AAA alkaline battery.

## Types of Batteries

Batteries are basically classified into 2 types:
Non-rechargeable batteries (primary batteries)
Rechargeable batteries (secondary batteries)

### Non-rechargeable Batteries

These are basically considered as primary batteries because they can be used only once. These batteries cannot be recharged and used again. Let’s see about the regular, daily life primary batteries that we see.
Alkaline batteries: It is basically constructed with the chemical composition of Zinc (Zn) and Manganese dioxide (MnO2), as the electrolyte used in it is potassium hydroxide which is purely an alkaline substance the battery is known as as alkaline battery having he power density of 100 Wh/Kg.

1. Cycle life is more.
2. They are more efficient and capable of powering portable devices.
3. Shelf life is more.
4. Small in size.
5. Highly efficient.
6. Low internal resistance in order that discharge state in idle state is a smaller amount.

### Coin cell batteries

The chemical composition of coil cell batteries is also alkaline in nature. Apart from alkaline composition, lithium and silver oxide chemicals will be used to manufacture these batteries which are more efficient in providing steady and stable voltage in such a small sizes. It has Power density of 270 Wh/Kg.

1. Light in weight
2. Small in size
3. High density
4. Low cost
5. High nominal voltage (up to 3V)
6. Easy to get high voltages by arranging serially
7. Long shelf life

1. Needs a holder
2. Low current draw capability

#### Applications:

Used in watches, wall clocks, miniature electronic products etc.

### Rechargeable Batteries

These are generally called as secondary batteries which can be recharged and can be reused. Though the cost is high, but they can be recharged and reused and can have a huge life span when properly used and safely charged.

It consists of lead-acid which is very cheap and seen mostly in cars and vehicles to power the lighting systems in it. These are more preferable in the products where the size/space and weight doesn’t matter. These comes with the nominal voltage starting 2V to24V and most commonly seen as 2V, 6V, 12V and 24V batteries. It has Power density of 7 Wh/Kg.

1. Cheap in cost
2. Easily rechargeable
3. High power output capability

1. Very heavy
2. Occupies much space
3. Power density is very low

#### Applications:

Used in cars, UPS (uninterrupted Power Supply), robotics, heavy machinery etc..

### Ni-Cd batteries

These batteries are made of Nickel and Cadmium chemical composition. Though these are very rarely used, these are very cheap and their discharge rate is very low when compared to NiMH batteries. These are available in all standard sizes like AA, AAA, C and rectangular shapes. The nominal voltage is 1.2V, often connected together during a set of three which provides 3.6V. It has Power density of 60 Wh/Kg.

1. Cheap in cost
2. Easy to recharge
3. Can be used in all environments
4. Comes in all standard sizes

1. Lower power density
2. Contains toxic metal
3. Needs to be charged very frequently so as to avoid growth of crystals on the battery plate.

#### Applications:

Used in RC toys, cordless phones, solar lights and mostly in the applications where price is important.

### Ni-MH batteries

The Nickel – Metal Hydride batteries are much preferable than Ni-Cad batteries due to their lower environmental impact. Its nominal voltage is 1.25 V which is bigger than Ni-Cad batteries. It has less nominal voltage than alkaline batteries and that they are good replacement thanks to its availability and fewer environmental impact. The power density of a Ni-mAh battery is 100 Wh / Kg.

1. Available in all standard sizes.
2. High power density.
3. Easy to recharge.
4. A good alternative to alkaline which has almost all similarities and also it is rechargeable.

1. Self-discharge is very high.

#### Applications:

Used in all applications almost like the alkaline and Ni-Cad batteries.

### Li-ion batteries

These are made from Lithium metal and are latest in rechargeable technology. As these are compact in size they will be utilized in most of the portable applications which require high power specifications. These are the best rechargeable batteries available. These have a nominal voltage of 3.7V (most commonly we have 3.6V and 7.2V) and have various ranges of power capacity (starting from 100s of mAh to 1000s of mAh). Even the C-rating ranges from 1C to 10C and Power density of Li-ion batteries is 126 Wh/Kg.

1. Very light in weight.
2. High C-rating.
3. Power density is very high.
4. Cell voltage is high.

1. These are a bit expensive.
2. If the terminals are operated low. Then the battery can explode.
3. Battery protection circuit is needed.

Li-Po batteries

These are also called as Lithium Ion polymer rechargeable batteries because it uses high conductivity polymer gel/polymers electrolyte instead of liquid electrolyte. These come under the Li-ion technology. These are a bit costly. But the battery is extremely highly protected in comparison to the Li-ion batteries. It has Power density of 185 Wh/Kg.

1. These are highly protective compared to Li-ion batteries.
2. Very light in weight
3. Thin in structure when compared to Li-ion batteries.
4. The power density is comparatively much higher than Ni-Cad and Ni-MH batteries at nominal voltage.

1. Expensive.
2. Might explode if wrongly connected.
3. Should not be bent or exposed to heat which can cause to explosion.

#### Applications:

Are often utilized in all the portable devices which require rechargeable advantage like drones, robotics, RC toys etc.

1. Thes are highly protective compared to Li-ion batteries.
2. Very light in weight
3. Thin in structure when compared to Li-ion batteries.
4. The power density is comparatively much higher than Ni-Cad and Ni-MH batteries at nominal voltage.

1. Expensive.
2. Might explode if wrongly connected.
3. Should not be bent or exposed to heat which can cause to explosion.

#### Applications:

Are often utilized in all the portable devices which require rechargeable advantage like drones, robotics, RC toys etc.

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