BATTERIES

Batteries – Lead Acid Battery; charging & discharging process of battery; maintenance of battery; Health check of battery; Lithium-ion battery; AA & AAA battery; car battery; Car battery charging process;

What is battery – Definition of battery is given below –

Definition –

a container consisting of one or more cells, in which chemical energy is converted into electricity and used as a source of power. Batteries are of two types – Lead Acid Battery  &  2) Sealed Maintenance Free (SFM) Battery

  • LEAD ACID BATTERY – A lead acid battery is also known as tubular battery. A battery consists of four main parts – a) a container which can hold liquid acid, b) Positive Electrode – Led PerOxide(PbO2) c) Negative electrode – Sponge Lead (Pb) & d) Electrolyte (Sulfuric Acid (H2SO4). The container is filled with Sulfuric acid (H2SO4)& major portion of positive & negative electrodes are dipped in the sulfuric acid & some portion of these electrodes are left out which are used to connect the load.

When we buy a led acid battery, say, 12V, it comes in two parts – 1) battery with a container &two electrodes fixed with the container, 2) Sulfuric acid which comes in a separate container. Now let us prepare battery so that it can be sued. Let us follow this procedure – first fill the container with sulfuric acid (H2SO4). Sulfuric acid with water in 3:1 ratio is called electrolyte.Connect battery with charger & leave it for 8-10 hrs. After sufficient charging, check battery voltage between positive (P)& negative (N) terminals. If 12V available between P&N terminals battery is ready for use, if voltage is less than 12V, then again charge it till voltage reaches up to 12V. The operation of a battery works on chemical reactions which can be understood from following diagrams-

The above process is called discharging of battery.

Now, Battery charging is done as per following procedure –

  • Connect discharged battery with charger.
  • Sulfuric Acid (H2SO4) remains in the solution of PbSO4 in the form of H+ & SO4 – -,
  • As H+ ion is positive so it will go to negative side of the battery which is connected with negative terminal with DC source & H+ ion becomes H atom by receiving electrons from it.
  • These hydrogen atoms attract PbSO4 and form Lead & Sulfuric Acid,
  • SO4 – – ions will attract towards positive terminal of battery &give up extra electrons become SO4 radicals,
  • These radicals react with PbSO4 & form PbO2 and H2SO4.

So, above process – 1)increases gravity of sulfuric acid&potential difference between two terminals. 2) Lead sulfate of negative plate gets converted into lead peroxide & lead sulfate of positive terminal gets converted into pure lead.

  • Following chemical reactions take place during discharging of batteries -H2SO4 =   H+(ions)  + SO4 – – (ions)
  • PbO2 + 2H =  PbO + H2O,
  • PbO + H2SO4 =  PbSO4 + H2O,
  • PbO2+ H2SO4 + 2H =  PbSO4 + 2 H2O,
  • Pb + SO4 – – = PbSO4

IMPORTANT POINTS TO REMEMBER –

  • Voltage & specific gravity – A fully charged cell has a voltage of 2.2V & specific gravity of 1.250 respectively.
  • Longer life of battery –Forlonger life of battery, a cell should not be allowed to be discharged till voltage 1.8V & 1.1level of specific gravity.
  • Ampere Hours (AH) – An ampere hour is the amount of energy charge in a battery that will allow oneampere of current to flow for onehour.
  • Series connection of batteries – Voltage of each battery adds up & current remains same. Total voltage& current of batteries when connected in series V = V1+V2+V3+…, Total Current I = I1 = I2 = I3 =

So, to make a 12V battery, 6 cells should be connected in series.

Example – When 2nos 12V, 100AH batteries are connected in series, total voltage would be 2X12V = 24V & total ampere would be 100AH only.

  • Parallel connection of batteries – Voltage remains same & current add up. So, in order to increase number ampere hours batteries should be connected in parallel.

Example– 2 nos of 12V, 100AH batteries are parallel connected, then total voltage will be 12V but ampere hours would be double 200AH (=100+100 AH)

  • When batteries are made, they are first charged by electrical supply.
  • Hydrogen gas – When water (H2O) decomposes during charging of batteries, oxygen bubbles collects at positive plate & hydrogen bubbles at negative plate. This reaction is producing hydrogen gas which is highly explosive when mixed with air. This in turn loss of electrolyte.
  • Battery Recycling –Roughly 95% are batteries are recycled. A lead acid batteries contain 60-80% lead & plastic, so these two items are used again & again by battery manufacturers. So batteries have great contribution towards environment.
  • Electrolyte –A chemical compound that ionizes when dissolved or molten to produce an electrically conductive medium. In lead acid battery, solution of Sulfuric Acid & water is an electrolyte.
  • Avoid deep discharges – The deeper the discharge, the shorter the battery life will be. A brief charge on a 1–2 hour break during heavy use prolongs battery life.

MAINTENENC OF BATTERIES–

  • Over Charging of battery –Cells should not be over charged, If cells are overcharged, physical properties of Lead Sulfate (PbSO4) gradually changes which decreases the specific gravity of electrolyte that hampers the rate of chemical reaction.

The color of sulfated plate becomes lighter & its surface becomes harsh & gritty. To avoid this, charging of battery should be done at low rate of charging current.

  • Refilling of lead acid battery –The level of electrolyte (mixture of water & sulfuric acid) in battery goes down due to two reasons – it evaporates naturally & secondly, hydrogen & O2 are produced in small amount during the operations.

If level of water goes down below the top the plates, the exposed plates sulfate& become inactive. So, batteries should be refilled with distill only (not from tap water & sulfuric acid). Because, the minerals of tap water affects the performance of batteries and acid increases the specific gravity which causes excessive corrosion.

  • Ventilation in battery rooms–As there is a production of hydrogen gas (in small amount) during charging/discharging process & there may be chances of spillage of electrolyte, these two things may pollute the atmosphere of battery room. Hence, battery room should be specious & proper ventilated.
  • Acid Stratification –When electrolyte concentrates at the bottom of plates & upper portion remains less concentration, this situation is called acid stratification.

This happens when battery remains at low voltage, never receives full charge & has shallow discharge. This causes following disadvantages – a) light acid on top plate limits activation, promote corrosion & reduces performance, b) high acid concentration on bottom makes the battery appear more charge (than actual). Battery shows an artificial full voltage, c) high concentration on bottom induces sulfating on lower half of plates.

Solution – Allowing the battery to rest for a few days. Doing a shaking motion or tipping the battery on its side helps correct the problem. Applying an equalizing charge by raising the voltage of a 12-volt battery to 16 volts for 1–2 hours also helps by mixing the electrolyte through electrolysis. Avoid extending the topping charge beyond its recommended time.

Frequently Asked Questions (FAQs) on Batteries–

Q1) How to check the health of a battery?

Ans) There are two types of batteries normally used for different instruments/devices – 1) batteries for small instruments/devices like mobile phone, AA batteries, AAA batteries etc 2) large batteries like lead acid batteries which are used for major equipment/devices like cars etc.

A) Health check-up of small batteries –

Health check-up for small batteries like for mobile phones, toys etc – there is no such mechanism to check the health status, but we need to check on the temperature & contact terminals if a device is not working properly.

Temperature – If temperature of the battery is increasing then we should take appropriate action to cool it down e.g. stop using that device for some time or if we are working in high temperature area then we should take it to normal temperature / cool place.

Contact terminals – Sometimes a device doesn’t work properly when battery terminals got rusted. This happens when we use the device in humid area or the terminals have come in contact with water. The rust/oxidation reduce the contact area between battery terminal & device’s terminal. This problem can rectified by removing the battery from the device then remove the rust & clean both battery & device terminals. If even after taking such precaution, device is not working then we should replace the battery.

B) Health Check up of large batteries –

On the other hand, large batteries have some health check points to maintain the voltage level of batteries such as –

  • Water level should be checked on regular basis (in lead acid batteries),
  • Specific gravity of electrolyte in each cell of the battery should be checked on regular basis. Its standard value is 1.260. if this value goes down, then battery will not be charged properly & create problem.
  • Loose terminal contacts – check tightness of wires with battery terminals so that battery supply to engine & charging of batteries are ensured. Loose contacts cause sparking at terminals & carbon particles would be deposited between wire & battery terminals. This condition will interrupt the charging process of battery.
  • Corrosion/oxidation of battery terminals – It is the tendency of the battery terminals to get oxidation when moisture is present around it. This oxidation will impact the contact between battery & wire terminals which in turn impact the battery charging. Therefore, such deposition of carbon particles should be checked on regular basis & if it is visible then clean the terminals properly & apply some gel/grease on the terminals to avoid further oxidation.
  • Check charging current also, the function of charger is to charge the battery & disconnect automatically. If auto disconnection is not happening & battery is continuously getting supply then this condition may damage the battery. Therefore, it is important to check the value of charging current, it should not be more than recommended by device/instrument manufacturer & auto-disconnection of charger should be working.

Q2) What is Lithium -ion battery?

Ans) Lithium -ion batteries are the most popular latest technology batteries which are being used in the equipment/devices where higher energy storage is required in less weight / dimension such as electric vehicles, mobile phones, laptops etc. In simple words we can understand the difference between a normal lead acid battery & lithium-ion battery, the storage capacity of a lead acid battery is approx. 25 Watt-hr while lithium-ion batteries storage capacity is approx. 150 watt-hr.

Construction of Lithium-Ion Battery–

Its design is similar to other batteries as it has one anode, one cathode, a separator & electrolyte. The Anode, Cathode & Separator are assembled in a metal case/container where they are submerged in an electrolyte. In this configuration Anode (Lithium-cobalt-oxide) acts as a positive electrode while cathode (carbon) acts as a negative electrode. These two electrodes are separated by a thin sheet of separator which is made up of micro-perforated plastic. Generally, ether is used as an electrolyte.

Working of Lithium-ion Battery –

In Lithium-ion batteries, ions are transferred between anode & cathode during charging & discharging of batteries while chemical reaction is required in conventional batteries.

During charging of batteries – lithium-ions are transferred from anode (positive electrode) to cathode (negative electrode) & during discharging – Li-ion moves back to anode from cathode & thus complete the cycle of battery. Per cell of Li-ion battery produces 3.5V which higher than any other type of batteries.

Q3) What is AA battery & AAA battery?

Ans) AA & AAA are standard cylindrical batteries which are used for domestic / portable equipment purpose. They are normally designed for 1.2 to 1.5 terminal voltage. The basic difference between AA & AAA batteries is the size & capacity.

AAA batteries are of small size (as compared to the AA) & used where less energy consumption is required such as TV remote, clocks etc. On the other hand, AA batteries are heavy duty & consume more energy, therefore they are used where more power is required such as toys etc.

(Note- we can’t use AA battery in place of AAA battery because of its sizes. Each battery operated equipment/device is designed for a specific battery size & power requirement where number of batteries & size of batteries sections are considered during manufacturing.)

Q4) What is Car battery? What is the specification of car battery?

Ans) Battery is a small part of any vehicle but plays an important role in it. A battery plays following role in a vehicle –

  • To start the vehicle or to ignite the engine. It works like this, when we switch on the vehicle by pressing the start button or by rotating car key, a signal is sent to car battery. The moment battery receives signal, it releases the energy (stored power) or give power to crank the engine.
  • Power steering & power brake. Without battery steering & brake behaves differently & become hard that needs more muscle power when we use them.
  • Playing radio
  • Power to lighting system of the vehicle such as head light, indicator, tail light, cabin light etc
  • Power to electrically operated sunroof & other electrical accessories.

Car Battery specification –

A car battery should have following characteristics-

  • Type of battery – Sealed lead acid type battery is suitable for 4 wheelers. These are maintenance free batteries as they don’t need water toping up & other maintenance. It is replaced when battery doesn’t produce enough voltage. (Note- We should ensure that terminals of the batteries are properly connected with wires (not loose or should not have oxidization).
  • Battery voltage– Normally, car batteries are available at 12V. A battery is considered fully charged when it’s voltage is 12.6 V or more.
  • Battery capacity – Battery capacity is available in Ah (Ampere hour) which represents the duration of the battery. More Ah means more durable battery in terms of power availability when vehicle is off. Generally, Ah value of battery varies from 32Ah to 180 Ah. But, it is not advisable to go with higher rating Ah. Ah rating of battery depends on the type of vehicle & its electrical accessories. Therefore, we should go for Ah rating as per car manufacturer’s recommendation.
  • Dimension of battery – The size of the battery varies with Ah rating, more capacity means battery size is more.
  • Weight of the battery – Weight of the battery also varies with Ah capacity. More Ah means more weight of the battery. The weight of battery varies company to company for same Ah also.
  • Cold Cranking Ampere (CCA) – Vehicle engine is needed some power to crank / start it. CCA is a rating that measures cranking power of the battery. CCA depends on many factors such as temperature, type of engine etc. CCA rating or number refers the amount of current that a battery can produce at 0 deg F (or 18 deg C) for 30 seconds. In other words, we can say that more CCA rating means easy to start the vehicle. Batteries with CCA ratings are available from CCA 220 to CCA 830. (CCA value of batteries may vary according to manufacturer.)

Q5) How a car battery gets charged?

Ans) Battery installed in a car is used for many purpose such as engine cranking, for power steering & brake & other accessories, therefore it is very important that battery should be rechargeable type otherwise vehicle will not work after first use of battery.

For charging of battery, electrical power is required. This power comes through the alternator which is installed in the vehicle. This alternator is nothing but a small generator which needs mechanical input to produce electricity as output. The alternator is connected with the engine through a belt which provide rotation to the rotor & electricity is produced in the stator (in ac form) which is converted into dc by a rectifier so that it could be fed to battery for charging. This how battery gets charged when not in use.