A single unit of electro-chemical generator is known as an Electrical Cell and a combination of several such units or electric cells that are electrically connected is called as a battery.

A battery is formed by combining several cells and connecting them electrically in series or parallel to form a battery with two main terminal electrodes, one positive and one negative.

Cathodes are elements with the highest negative electrode potential, while anodes are elements with the highest positive electrode potential. The terminal voltage is provided by the difference between the electrodes. The electrical potential difference between the two main electrodes is determined by the number of cells, cell type, and combination used to create the battery.

The battery generates electrical energy through an electrochemical reaction between two metals with different affinities. When metals are exposed to acids, a voltage develops between them as a result of ion transfer, and closing the circuit induces a current.

An electrical battery is represented by the following symbol in electronic circuits and diagrams:

 Electric Battery Symbol

 A battery is rated in ampere-hours (Ah). This specifies how much charge a pack can hold.

Batteries are made to order for a specific use, and manufacturers are well aware of consumer demands. The mobile phone and electric vehicle markets are two instances of creative adaptations at opposing ends of the spectrum. Unlike consumer batteries, which prioritise small size, high specific energy, and low cost, industrial batteries prioritise consistent performance and long life. The importance of safety in all applications cannot be overstated.

Battery in Series connection:

Higher operating voltages can be obtained by connecting the positive terminal of one cell to the negative terminal of another. When we connect our batteries in series, we double the voltage while keeping the same capacity rating (amp hours). This could be used in a scooter, a Power Wheels vehicle for kids, or other applications. We could simply connect the negative of the first battery to the positive of the second battery with a jumper wire.

 Battery in Series connection

  Battery in Parallel connection:

In parallel connection, although the capacity will be increased, the power supply will be provided by one of the individual batteries. To put it another way, when batteries are connected in parallel, the voltage remains constant while the power (or available current) increases. As a result, the batteries will last longer. In other words, the two batteries could power a 6 Volt item for twice as long as a single battery could.

To connect two batteries in parallel, use a jumper wire to connect both positive terminals and another jumper wire to connect both negative terminals of both batteries.

 Battery in Parallel connection

Batteries are classified according to three factors: chemistry, voltage, and specific energy (capacity). A starter battery also produces cold cranking amps (CCA), which refers to its capacity to provide high current at low temperatures.


Lead, nickel, and lithium are the most popular battery chemistries, and each system requires its own charger. Charging a battery with a charger made for a different chemistry may appear to operate at first, but the charge may not be properly terminated. When transporting and disposing of batteries, keep in mind that each chemistry has its own set of regulations.


Although batteries are labelled with their nominal voltage, the open circuit voltage (OCV) on a fully charged battery is 5–7% higher. The OCV is determined by chemistry and the number of cells connected in series. The operating voltage is the closed circuit voltage (CCV). Before connecting a battery, always check for the correct nominal voltage.


Capacity represents specific energy in ampere-hours (Ah). The discharge current that a battery can provide over time is measured in Ah. You can install a battery with a higher Ah than specified for a longer runtime; alternatively, you can use a slightly smaller pack for a shorter runtime. Chargers are tolerant of Ah rating differences (with the same voltage and chemistry); a larger battery will simply take longer to charge than a smaller pack, but the Ah difference should not exceed 25%.

Cold-cranking amps (CCA):

CCA is stamped on starter batteries, also known as SLI (starter light ignition). The number represents the ampere-hour current that the battery can deliver at –18°C (0°F). The norms in the United States and Europe differ slightly.

Types of Battery:

Based on the electric properties batteries can be classified into two main groups:

Primary Battery:

Primary battery is the type of battery which is made up of primary cells (In a primary cell chemical reaction is irreversible). The energy is inherently present in the cells of Primary Battery. These kind of batteries are non-rechargeable and are for single time use. Batteries used in hearing aids (zinc air type) are primary. All AAA, AA, and A type in torches, remote etc are also primary batteries. Examples of primary battery are: Leclanche battery, zinc-chlorine battery, alkaline-maganese battery, metal air battery etc.

Secondary Battery:

Secondary batteries, often known as 'rechargeable batteries', are widely used everywhere. We use them in our house inverter, mobile phones, automobiles and trucks, and rechargeable flashlights.

A secondary battery is built up of secondary cells. Prior to use, energy is induced in the chemistry of the secondary battery's cells by applying external energy or sources. Chemical reactions in secondary cells are reversible.

Many daily activities would be impossible to complete without the ability to recharge rechargeable batteries. Lead acid, NiCd, NiMH, and Li-ion are the most common rechargeable batteries. Here's a quick rundown of their characteristics.

  • Lead Acid – This is the most conventional rechargeable battery system. Lead acid batteries are tough, forgiving if abused, and reasonably priced, but they have a low specific energy and a limited cycle count. Lead acid batteries are used in wheelchairs, golf carts, personnel carriers, emergency lighting, and backup power supplies (UPS). Lead is toxic and should never be disposed of in a landfill.
  • Nickel-cadmium – NiCd is a mature and well-understood material that is used in applications requiring long service life, high discharge current, and extreme temperatures. NiCd batteries are among the most durable and long-lasting; they are the only chemistry that allows for ultra-fast charging with minimal stress. Power tools, medical devices, aviation, and UPS are the most common applications. NiCd is being replaced with other chemistries due to environmental concerns, but it retains its status in aircraft due to its good safety record.
  • Nickel-metal-hydride – A replacement for NiCd because it contains only mildly toxic metals and has a higher specific energy. NiMH is used in medical devices, hybrid vehicles, and industrial applications. For consumer use, NiMH is also available in AA and AAA cells.
  • Lithium-ion – Li-ion batteries are replacing lead and nickel-based batteries in many applications. Li-ion requires a protection circuit due to safety concerns. It is more expensive than most other batteries, but the high cycle count and low maintenance lower the cost per cycle when compared to many other chemistries.


All batteries pose a safety risk, and battery manufacturers are required to meet safety standards.

Lithium-ion batteries are safe, but with millions of people using them, failures are unavoidable.

Battery failures are classified into two types. One occurs at a predictable per-million interval and is associated with a design flaw involving the electrode, separator, electrolyte, or processes. These flaws frequently necessitate a recall to correct a discovered flaw. The more difficult failures are random events that do not indicate a flaw in the design. It may be a stress event like charging at sub-freezing temperature, vibration, or a fluke incident that is comparable to being hit by a meteor.

Cell failure can also be caused by uneven separators. Poor conductivity due to dry areas increases resistance, which can result in local heat spots that compromise the separator's integrity. Heat is the battery's worst enemy.

What Should You Do If Your Battery Overheats or Catches Fire?

If a Li-ion battery overheats, hisses, or bulges, remove it from flammable materials and place it on a non-combustible surface right away. Remove the battery and leave it outside to burn out if at all possible. Simply disconnecting the battery from power may not be enough to stop its destructive path.

A small Li-ion fire can be handled in the same way as any other combustible fire. Use a foam extinguisher, CO2, ABC dry chemical, powdered graphite, copper powder, or sodium carbonate for the best results. If a fire breaks out in a plane's cabin, the FAA advises flight attendants to use water or soda pop. Water-based products are the most widely available and appropriate because Li-ion batteries contain very little lithium metal, which reacts with water. Water also cools the surrounding area and keeps the fire from spreading.

Sand stored in a fire-proof bucked is a readily available and effective fire retardant. In the event of a fire, the flaming battery is moved into the bucked and covered with sand, allowing for a controlled burn-out. Sand can also be thrown over the hot battery to keep it from spreading.

While lithium-ion batteries have been extensively studied for safety, nickel- and lead-ion batteries have also caused fires and are being recalled. The reasons for this are faulty separators caused by ageing, rough handling, excessive vibration, and high temperatures. When used correctly, lithium-ion batteries have become extremely safe, with heat-related failures occurring only infrequently.


Lead-acid batteries:

To keep lead acid batteries in good condition, apply a fully saturated charge that lasts 14 to 16 hours. If the charge cycle does not allow it, fully charge the battery once every few weeks. If possible, operate at a moderate temperature and avoid deep discharges; charge as frequently as possible.

Nickel-based batteries:

Although modern nickel-cadmium batteries no longer have cyclic memory, they do suffer from crystalline formation. If a nickel-based battery is left in the charger for days or repeatedly recharged without a full discharge, crystalline formation occurs. Because the majority of applications fit this user profile, NiCd requires a periodic discharge to 1 volt per cell to extend service life. A discharge/charge cycle, also known as exercise, should be performed as part of routine maintenance every 1–3 months. Excessive exercise depletes the battery unnecessarily.

If regular exercise is not performed for 6 months or longer, the crystals become ingrained, and a full restoration with a discharge to 1 volt per cell may no longer be sufficient. Restoration is frequently possible by using a secondary discharge known as recondition. Reconditioning is a slow discharge that reduces the battery voltage to 0.4V/cell or lower.

Lithium-based batteries:

Battery research is so focused on lithium chemistries that one might think the battery's future is solely in lithium. Applications are expanding and encroaching on markets that were previously dominated by lead acid. The longevity of lithium-ion batteries is determined by environmental factors rather than cycling alone. The worst case scenario is keeping a fully charged battery at high temperatures. Battery packs do not die suddenly, but their runtime decreases gradually as their capacity depletes.

Lower charge voltages extend battery life, which is used by electric vehicles and satellites.

Modern laptops run cooler than older models, and there have been fewer reported fires. When using electric devices with air-cooling on a bed or pillow, always keep the airflow clear. A cool laptop increases battery life and protects internal components. Energy Cells, which are found in most consumer products, should be charged at 1C or less. Avoid so-called ultra-fast chargers that claim to charge Li-ion batteries in under an hour.



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