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Basics of Cells & Battries

Reading Time: 7 minutes

Cells or Batteries are broadly classified into two four broad categories:

  • Primary cell
  • Secondary cell
  • Reserve cell
  • Fuel cell


Let us start with basic definition of these cells:

Primary cell:

  1. primary cell or battery is one that cannot easily be recharged back.
  2. Generally these cells contain electrolyte in the form of solid powdered state and that’s why these are also known as DRY CELLS.
  3. Cells contain electrochemical reactions which are non –reversible.
  4. These are having very low self discharge rate known as charge retention factor. Factors affecting self-discharge extent include: anode and cathode preparation course, electrolyte nature and concentration, and battery storage temperature and time, among which battery self discharge greatly depends on temperature.
  5. Examples: Zn–MnO2 cell which is most commonly used battery. This type of battery is available in different sizes- AA, AAA, C, D etc.

We discuss later on what is the difference in between them in terms of electrochemistry.


Let us understand electrochemistry of Zn –MnO2 cell:


Understanding electrochemistry of any battery always divides the cell into separate anode region, cathode region, electrolyte used and separator material which separate anode and cathode.

So, here we have Zn metal at anode which reacts with electrolyte ammonium chloride as follows:

Zn(s) + 2OH(aq) → ZnO(s) + H2O(l) + 2e [e° = 0.76 V]

Emf(Ox) = 0.76 – RT/2F ln([Zn0]/[OH-]^2)……nernst equation


At  cathode MnO2 is there which will reat with two e-‘s on cathode eletrode surface i.e.

2MnO2(s) + H2O(l) + 2e → Mn2O3(s) + 2OH(aq) [e° = +0.5 V]

Emf (Red) = 0.5 – RT/2F ln ([Mn2O3]/[MnO2^2])


Add both anodic and cathodic half cell reactions we get:


Zn +MnO2 –>ZnO2 + Mn2O3


Emf total = Emf (ox) + Emf (red)

= +1.56 –RT/2F ([Mn2O3][ZnO2]/[MnO2])

The above process is discharge of cell but if we consider discharge of a battery we have to reverse the above reactions but thermodynamically this process is infeasible, and that’s why we cannot charge primary cells.

Secondary cell:

  1. Electrochemical reaction occurring in reversible in nature ,therefore we can recharge them
  2. e.g. : lead–acidnickel cadmium (NiCd), nickel metal hydride (NiMH), lithium ion(Li-ion), and lithium ion polymer (Li-ion polymer).

Lead Acid Battery

Lead–acid batteries, invented in 1859 by French physicist Gaston Plante, are the oldest type of rechargeable batteries. This is most widely used commercial battery used in    automobiles and heavy electronic devices because of its high current rating.

Let’s understand the mechanism of lead acid batteries:

Negative plate reaction: Pb(s) + HSO−4(aq) → PbSO4(s) + H+(aq) + 2e-

Positive plate reaction: PbO2(s) + HSO−4(aq) + 3H+(aq) + 2-e → PbSO4(s) + 2H2O(l)


Overall reaction: Pb(s) + PbO2(s) + 2H2SO4(aq) → 2PbSO4(s) + 2H2O(l)



Applying Nernst equation at room temperature for this case we get 2v.

I.e. Per cell voltage is 2v.Therefore 6 cells are stacked together to form 12v battery having 13.9 amp-hours per kg.


 Similarly we can think of Lithium ion battery, they are one of the most popular types of rechargeable battery for portable electronics, with one of the best energy densities, and only a slow loss of charge when not in use.




Positive electrodes: LiCoO2- =   Li1-x CoO2 + xLi + xe-
Negative electrodes:  C+xLi+xe-  =   CLix

Battery as whole:    LiCoO2 + C  =   Li1-x CoO2+CLix
<– charging

  • During discharge, lithium ions Li+ carry the current from the negative to the positive electrode, through the non-aqueous electrolyte and separator diaphragm.
  •  Picture4Picture5
  • Pure lithium is very reactive. It reacts vigorously with water to form lithium hydroxide and hydrogen gas. Thus, a non-aqueous electrolyte is typically used, and a sealed container rigidly excludes water from the battery pack.



Now next is Reserve batteries :

  •  These batteries are working as normal batteries but cell is inactive (dead) until and unless cell certain condition is not fulfilled.
  •  These batteries are used in radio sondes, missiles, projectile and bomb fuzes, and various weapon systems. Generally these are used for military purposes.
  •  Another example is zinc-air batteries where the cell is sealed until use: a tab is removed to admit air and activate the cell.
  •  It can be activated by: Addition of water, Addition of electrolyte, Introducing gas into the cell, heating solid electrolyte (solid-oxide fuel cell) so that it becomes conductive and there may be many other ways by which we can activate these cells.

Fuel cell

fuel cell is a device that converts the chemical energy from a fuel into electricity through a chemical reaction with oxygen or another oxidizing agent.

Hydrogen is the most common fuel, but hydrocarbons such as natural gas and alcohols like methanol are sometimes used.

Fuel cells are different from batteries in that they require a constant source of fuel and oxygen to run, but they can produce electricity continually for as long as these inputs are supplied. For e.g. in Zn-Air fuel system if continuous supply of O2 at cathode and simultaneously removal of ZnO (by product) from anode we can get power continuously.


For e.g.- Hydrogen fuel cell, Microbial fuel cell etc.

So, until now we have discussed types of batteries, let us now understand basic things which very essential to understand any battery :


Terminology used in Electrochemistry:

1) Ampere hour: It is the amount of current supplied by the battery in one hour.

e.g.: 30mAhr means when connected to a load of rating 5 mAhr then load will work for 6 hrs .When cells are stacked together then ampere hr rating is return of per kg of cell.

2) Energy Density:  It is how much energy can be stored per unit volume or mass of a battery. It is expressed in joules per unit mass. MJ/kg

3) Power Density: It is basically how quickly energy is taken out from battery.It is expressed in kW/kg

4) Self discharge rate: it is process in which cell stored internal energy is decreased. self- discharge in a battery occurs is dependent on the type of battery, state of charge, charging current, ambient temperature and other factors.

Among rechargeable batteries, lithium batteries suffer the least amount of self-discharge (around 2–3% discharge per month), while nickel-based batteries are more seriously affected by the phenomenon (nickel cadmium, 15–20% per month; nickel metal hydride, 30% per month).



Now let us understand on what factors cell voltage, internal resistance depends:

Cell Parameters


1)     CELL VOLTAGE : it depends upon concentration of chemicals.

  • E call= Rt/nF*ln[k]….Nernst equation
  • Where k depends upon concentration of reactants and products. Now when cell discharges reaction will go in forward direction till equilibrium is reached.(le chatlier principle).Then cell is considered as dead. Now we have to recharge the cell to increase [] of product side.

For e.g. we have AA and AAA type of dry cell, so what is the difference in between them???


  • Diameter of AA battery is more AAA battery.
  • Both are having same voltage output as voltage output does not depends upon size of cell but depends upon concentration of electrolytes.
  • The only difference is of current rating which is less in AAA batteries as compared to AA. e.g.: AA, AAA, LITHIUM BATTERY, ALKALINE BATTERIES ETC.(’AA ’ means 50.5mm x 13.5mm.)



2)     Internal Resistence


  •   Resistance =ρ *l/a where l is length between electrodes and ‘a’ is surface area of electrodes.
  •  Now this constant ρ depends upon electrolyte concentration. In 90% batteries electrolyte work as catalyst but in few cells electrolyte is consumed .As electrolyte becomes less and less conductive .so result is increased resistivity of cell.

3)     Polarization curve: It is plot between voltage outputs of the battery versus % discharged.

Figure shown here is the polarization curve for most commonly used batteries. We can see here initial voltage drop then it remains constant and then finally voltage drops fast.






Other interesting stuffs:

The battery terminals are generally labeled as : + , – , T , and D or Do.
T is connected to an internal temperature sensitive component ( thermistor) . This is to prevent overheating of the battery so it is very important on safety point of view
D or Do is a newly introduced contact. It is a data line which allows Smartphone and battery to exchange information about current, voltage, temperature, residual battery capacity etc…. It has been introduced to improve % remaining battery capacity readings.






Application Of Electronics in Automobiles

Reading Time: 2 minutes



Automotive electronics or automotive embedded systems are distributed systems and according to different domains in the automotive field they can be classified into:

}        Engine Electronics

}        Transmission Electronics

}        Chassis Electronics

}        Active Safety

}        Driver assistance

}        Passenger Comfort

}        Infotainment systems


Engine Electronics

}        One of the most demanding electronic part of an automobile is the engine control unit. Engine controls demand one of the highest real time deadlines, as the engine itself is very fast and complex part of the automobile. Of all the electronics in any car the computing power of the engine control unit is the highest, typically a 32-bit processor.


In a Diesel Engine

}        -Fuel injection rate

}        -Emission control, Nox control

}        -Regeneration of oxidation catalytic converter

}        -Turbocharger control

}        -Cooling system control

}        -Throttle control


In a Gasoline engine


}        OBD OnBoard diagnosis

}        -Cooling system control

}        -Ignition system control

}        -Lubrication system control (only few has electronic control)

}        -Fuel injection rate control

}        -Throttle control


Transmission Electronics

}        This controls the transmission system; mainly it controls the shifting process of the gears. For a better shift comfort, lower torque interrupt while shafting -these electronics are used in a manual transmission. Many semi automatic transmissions which have a fully automatic clutch or a semi-auto clutch (only declutching) use electronics for its operation and control. Also fully automatic transmissions use controls for their operation.


Chassis Electronics


}        ABS – Anti-lock braking system

}        TC – Traction control system

}        EBD – Electronic brake distribution

}        ESP – Electronic Stability Program



Active Safety

}        Air Bags

}        Hill Descent Control

}        Emergency Brake assist system


Driver assistance

}        Lane assist system

}        Speed assist system

}        Blind spot detection

}        Park assist System

}        Adaptive Cruise Control System


Passenger Comfort

}        Automatic Climate control

}        Electronic seat adjustment with memory

}        Automatic wipers

}        Automatic Headlamps



}        Navigation system

}        Music system

               Information access






History & Latest Trends In Microcontroller & Microprocessor

Reading Time: 5 minutes


       Topics :-

  • –   Physical View of MPU & MCU
  • –   Moore’s Law
  • –   Key Features Of MPU & MCU
  • –    Bridge between College and Real Life Scenario-Work Of Intel Engineer
  • –   Latest in MPU & MCU
  • –   Leading Companies In MPU


Physical View of MPU & MCU:

Historical Background


  • –   Fairchild Semiconductors founded in 1957, invented the first IC in 1959.
  • –   In 1968, Robert Noyce, Gordan Moore, Andrew Grove resigned from Fairchild Semiconductors.
  • –   Found their own company Intel (Integrated Electronics).
  • –   Intel grows from 3 man start-up in 1968 to industrial giant by 1981.
  • –   It had 82,500 employees (2010) and $53.34 Billion revenue(2012).


  • –   1947-Invention Of Transistor
  • –   1959-Invention Of Integrated Circuit
  • –   1965-Birth Of Moore’s Law
  • –   1971-Development of First Microprocessor-4004
  • –   1971-Development of First Microcontroller-TMS1000
  • –   2011 May 2, , Intel announced its first 22 nm microprocessor, codenamed Ivy Bridge, using a technology called 3-D Tri-Gate


Gorden Moore’s Law

”The number of transistors on integrated circuits will double approximately every 24 months.”

 moores law

 So what changes do they do actually?

Bring in Advanced Micro-architecture technology which puts in more and more no. of transistors on a unit sized chip


Key Features Of MPU & MCU:

  • Smaller Size
  • Lower Cost
  • Higher Reliability
  • Lower Power Consumption-CMOS
  • Higher Versatility
  • More Powerful


Bridge between College and Real Life Scenario-Work Of Intel Engineer

What do these Engineers do?[1]

–   Process Engineers-develop the most efficient methods for semiconductor manufacturing using state-of-the-art equipment and materials

–   Yield Engineers– work closely with process engineers to improve product yield and to troubleshoot process flow from root causes to equipment tuning

–   Equipment Engineers–  own and lead the stability, improvement, maintenance and performance functions of extremely advanced tools

–   Design Automation and Computer Aided Design (CAD) Engineers– design, develop, maintain, and provide user support of CAD tools, assist with schematic entry and analysis in the integrated circuit design process, and create and implement computer-controlled automatic test systems. In all of these tasks, their core objectives are simple—to improve quality and reduce costs

–   Hardware and Software
Product Development- ensuring the testability and manufacturability of integrated circuits, optimizing component production, and evaluating, developing and debugging complex test methods. Working with our process technology development and product teams, these individuals help deliver the best process and design effective reliability models based on ROI, process limitations, Q&R requirements and product usage models

–   Component Design and Validation–  responsible for chip layout, circuit design, circuit checking, device evaluation, and validation. Starting with product requirements and logic diagrams, they plan design projects and help address the unique needs of our customers

–   Research and Development– Explore how customers interact with technology, what they love about it, and how to make off-the-wall ideas usable reality. Whether you’re applying new materials, emerging technologies or customer insights, your innovations will be what transforms the computing capabilities of tomorrow.


Latest in MPU & MCU:

What the hell is the difference between these i3 i5 and i7 Processors???

–   Cores-2(dual)–   3-4 MB Cache–   2.93 to 3.06 GHz Clock Speed –   Cores2(dual)/4(Quard)Threads-2/4–   4/(6-8) MB Cache–   3.2 to 3.6/2.4 to 2.6 GHz Clock Speed– Cores-4(quard)8 MB Cache3.06 to 3.2 GHz Clock Speed  
–   Threads-4 Threads 2/4Threads-8
–   Hyperthreading-Yes–   Hyperthreading-Yes/NoHyperthreading-Yes
–   Turbo Boost-No–   Turbo Boost-Yes/YesTurbo Boost-Yes
–   32 nm technology–   32/45 nm technology32-45 nm technology



Meaning Of Pratik has 64-Bit Laptop???

  • –   It means the Microprocessor has 64 data bus lines.
  • –   So if you have 32 bit Microprocessor, then it means that there are 32 data lines .

Meaning of 256 MB Memory

–   256 =2^8

–   So there are in total 8 address lines


Leading Companies In MPU:





  • –   Integrated Electronics founded in 1968
  • –   Paul Otellini –CEO
  • –   Headquarter-Santa Clara ,California
  • –   Intel has also begun research in electrical transmission and generation
  • –   It has 23,000 employers
  • –    Intel has recently introduced a 3-D transistor that improves performance and energy efficiency.
  • –   Intel has begun mass producing this 3-D transistor, named the Tri-Gate transistor, with their 22 nm process, which is currently used in their 3rd generation core processors initially released on April 29, 2012




 History & Latest Trends In Microcontroller & Microprocessor microcontroller vs microprocessorHistory & Latest Trends In Microcontroller & Microprocessor microcontroller vs microprocessorHistory & Latest Trends In Microcontroller & Microprocessor microcontroller vs microprocessor
History & Latest Trends In Microcontroller & Microprocessor microcontroller vs microprocessor History & Latest Trends In Microcontroller & Microprocessor microcontroller vs microprocessor History & Latest Trends In Microcontroller & Microprocessor microcontroller vs microprocessor


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Power of Nanotechnology

Reading Time: < 1 minute

Nanotechnology is the engineering of tiny machines. It is the projected ability to build things from the bottom up inside personal nano-factories (PNs) using techniques and tools being developed to make complete, highly advanced products.

Ultimately, nanotechnology will enable control of matter at the nanometre scale, using mechanochemistry. Shortly after this envisioned molecular machinery is created, it will result in a manufacturing revolution, probably causing severe disruption. It has serious economic, social, environmental, and military application.

One of the cool feature of Nanotechnology is the synthesis of Buckypaper from Carbon Nanotubes. A Carbon Nanotube is a tube-shaped material, made of carbon allotrope, having a diameter measuring on the nanometer scale. Carbon Nanotubes have many structures, differing in length, thickness, and in the type of helicity and number of layers. Although they are formed from essentially the same graphite sheet, their electrical characteristics differ depending on these variations, acting either as metals or as semiconductors.

Hence various essential properties can be obtained in one Buckypaper sheet at the same time because of the Carbon Nanotubes. Watch the video below to get more insight on how the use of Buckypaper will revolutionize our lives.


# References:

CEV - Handout