What is a battery?

A battery is an electrical device consisting of one or more electrochemical cells that convert stored chemical energy into electrical energy. Each battery consists of a positive electrode material (also called +ve plate), a negative electrode material (also called –ve plate), an electrolyte that allows ions to move between the electrodes, and terminals that allow current to flow out of the battery to perform work.

Batteries have much lower specific energy (energy per unit mass) compared to common fuels such as diesel/petrol. This is somewhat mitigated by the fact that batteries deliver their energy as electricity (which can be converted efficiently to mechanical work), whereas using fuels in engines entails a low efficiency of conversion to work.

What are the two main types of batteries?

The two main types of batteries are primary batteries and secondary batteries.

Primary batteries, also called primary cells, can produce current immediately on assembly.

Secondary batteries, also called secondary cells or rechargeable batteries, have to be charged before first use since they are assembled with active materials in the discharged state.

What are the characteristics of primary batteries?

Primary batteries, also called primary cells, can produce current immediately on assembly. These are most commonly used in portable devices that have low current drain, are used only intermittently, or are used well away from an alternative power source, such as in alarm and communication circuits where other electric power is only intermittently available.

Primary batteries transform chemical energy to electrical energy irreversibly. It means that when the supply of reactants is exhausted, energy cannot be readily restored to the battery, since the chemical reactions are not easily reversible and active materials may not return to their original forms. Therefore, primary batteries are also called disposable batteries because you are supposed to use them until they get discharged and then throw them away.

In general, primary batteries have higher energy densities compared to rechargeable batteries. But they do not fare well under high drain (or high current) applications with loads under 75 ohms.

Common types of disposable batteries include zinc-carbon and alkaline batteries.

What are the different types of primary batteries and how do they compare against each other?

Type

Nominal Cell Voltage

Specific Energy

Comments

 Zinc-Carbon

1.5

0.13

 Inexpensive

 Zinc-Chloride

1.5

 

 Inexpensive. Also known as “heavy duty”.

 Alkaline (Zinc-Manganese Dioxide)

1.5

0.4-0.59

 Moderate energy density. Good for high and low drain uses.

 Nickel Oxyhydroxide

1.7

 

 Moderate energy density. Good for high drain uses.

 LithiumCopper Oxide (LiCuO)

1.7

 

 No longer manufactured.

 Lithium Iron Disulfide (LiFeS2)

1.5

 

 Expensive. Used in “plus” or “extra” batteries.

 Lithium Manganese Dioxide (LiMnO2)

3.0

0.83-1.01

 Expensive. Used only in high drain devices or for long shelf life due to very low self-discharge rate.

 Mercury Oxide

1.35

 

 Used in high drain and constant voltage uses. Banned in most countries because of health and environment concerns.

 Zinc Air

1.35-1.65

1.59

 Used mostly in hearing aids.

 Silver Oxide

1.55

0.47

 Very expensive. Used only commercially in button cells.

What are the characteristics of secondary batteries?

Secondary batteries, also called secondary cells or rechargeable batteries, have to be charged before first use since they are usually assembled with active materials in the discharged state. Rechargeable batteries are (re)charged by applying electric current, which reverses the chemical reactions that occur during discharge/use. The devices that charge rechargeable batteries are called battery chargers.

What are the different types of secondary batteries and how do they compare against each other?

Type

Nominal Cell Voltage

Specific Energy

Comments

 Nickel Cadmium (NiCd)

1.2

0.14

  • Inexpensive.
  • Moderate energy density.
  • Good for high and low drain uses.
  • Can withstand very high discharge rates with no loss zof capacity.
  • Moderate self-discharge rate.
  • Environmental hazard due to cadmium which is toxic. Use virtually prohibited in Europe.

 Lead Acid

2.1

0.14

  • Moderately expensive.
  • Moderate energy density.
  • Moderate self-discharge rate.
  • Good for high and low drain uses.
  • High discharge rates result in considerable loss of capacity.
  • Environmental hazard due to lead.
  • Commonly used in automobiles.

 NiMH

1.2

0.36

  • Inexpensive.
  • Performs better than alkaline batteries in high drain uses.
  • Traditional chemistry has high energy density, but also high self-discharge rate.
  • Newer chemistry has low self-discharge rate but also 25% lower energy density.
  • Commonly used in cars.

 NiZn

1.6

0.36

  • Moderately inexpensive.
  • Good for high drain uses.
  • Low self-discharge rate.
  • Voltage closer to alkaline primary cells compared to other secondary cells.
  • No toxic components.
  • Newly introduced in 2009 and therefore has no track record.
  • Limited size availability.

 AgZn

1.86 1.5

0.46

  • Smaller volume than equivalent Li-ion.
  • Extremely expensive due to silver.
  • Very high energy density.
  • Capable of delivering very high drain currents.
  • Suffers from oxidation is unused.
  • Reactions are not fully understood.
  • Terminal voltage very stable but suddenly drops to 1.5 at 70%-80% charge.
  • Has been used in lieu of primary battery.
  • Is being developed once again as a replacement of Li-ion.

 Lithium Ion

3.6

0.46

  • Very expensive.
  • Very high energy density.
  • Not usually available in common battery sizes.
  • Very low self-discharge rate.
  • Terminal voltage unstable (varies from 4.2 to 3.0 during discharge)
  • Chance of explosion if short circuited, over heated, or not manufactured with rigorous quality standards
  • Very common in laptop computers, moderate to high end digital cameras, camcorders, and mobile phones.

What are the types of battery cells?

There are many types of electrochemical cells with varying chemical processes and designs. They are: electrolytic cells, galvanic cells, fuel cells, flow cells, and voltaic piles.

What is a wet cell?

A wet cell is a cell that has a liquid electrolyte. A wet cell is also called vented cell (since it has a vent to allow the gases produced to escape in the air) or flooded cell. A battery that has a wet cell is called a wet battery or vented battery or flooded battery.

Wet cells can be primary cells or secondary cells.

What is a dry cell?

A dry cell uses a paste electrolyte, with only enough moisture to allow the current to flow. Unlike a wet cell, a dry cell can operate in any orientation without spilling, as it contains no free liquid, making it suitable for use in portable equipment.

How is battery capacity measured?

A battery’s capacity is the amount of charge it can deliver at the rated voltage and is measured in terms of ampere-hours, which is popularly called Ah rating.

What is C10 rating of a battery?

C10 rating of a battery is the product of 10 hours and the maximum current that a new and fully-charged battery can consistently supply for 10 hours, without the voltage falling below a certain level. So for example, if a battery can deliver 5 amperes for 10 hours, its C10 rating will be 50 Ah.

C10 rating is very popular. More often than not, it is specified by default for batteries.

What is C20 rating of a battery?

C20 rating of a battery is the product of 20 hours and the maximum current that a new and fully-charged battery can consistently supply for 20 hours, without the voltage falling below a certain level. So for example, if a battery can deliver 5 amperes for 20 hours, its C20 rating will be 100 Ah.

C20 rating is very popular, probably second only to C10 rating.

What is C24 rating of a battery?

C24 rating of a battery is the product of 24 hours and the maximum current that a new and fully-charged battery can consistently supply for 24 hours, without the voltage falling below a certain level. So for example, if a battery can deliver 5 amperes for 24 hours, its C24 rating will be 120 Ah.

What is C100 rating of a battery?

C100 rating of a battery is the product of 100 hours and the maximum current that a new and fully-charged battery can consistently supply for 100 hours, without the voltage falling below a certain level. So for example, if a battery can deliver 5 amperes for 10 hours, its C100 rating will be 500 Ah.

Do the Cxx ratings change for a battery as xx changes?

Yes, for a battery, the Cxx ratings change. As you go to longer time durations (from C10 to C100), the current that you can draw from the battery goes on decreasing. However, the Ah rating goes on increasing. In other words, it means that the battery has larger capacity for longer time durations(with smaller currents) and lower capacity for shorter time durations (with higher currents).

So typically, for a battery, C10 < C12 < C20 < C24 < C48 < C100 will almost always be true. Similarly, as you go to shorter and shorter time durations, the Ah rating will on reducing. So, C10 > C8 > C5 > C4 > C3 > C2 > C1.5.

For example, for our 12V deep cycle VRLA AGM battery with 45Ah @ C10, the following table will illustrate the case in point. End VPC is 1.67V.

C Rating

C1.5

C2

C3

C4

C5

C8

C10

C12

C20

C24

C100

Ah Rating

32.6

34.2

37

38.5

39.6

43.2

45

46

50

50.9

57

Current (A)

21.7

17.1

12.3

9.63

7.92

5.40

4.50

3.83

2.50

2.12

0.57

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“End VPC” means the ending voltage per cell or VPC in short. It is the pre-decided voltage below which the voltage should not fall while discharging the battery for Ah rating measurements.

The lower the end VPC is allowed to go, the higher the Ah rating will come out to be and vice versa. And the reason for it straightforward: as you start discharging the battery, its voltage remains steady for a while and then starts reducing gradually. If you choose a lower end VPC, you will be able to draw the current for a longer time, and hence the Ah rating is bound to come out higher.

The C10 ratings for different end VPC values will illustrate its effect on Ah rating.

 No.

  End VPC

   Ah rating

 1.

  1.67

  45

 2.

  1.75

  43.8

 3.

  1.80

  40.9

What are the types of lead acid batteries?

There are two basic types of lead acid batteries: FLA (Flooded Lead Acid) and VRLA (Valve Regulated Lead Acid) batteries.

FLA batteries are the most common type of batteries that are used and are the ones that need to be periodically filled with distilled water to ensure that they don’t become dry. This periodic filling with distilled water is also called “topping up” or “doing top up”.

VRLA batteries, on the other hand, are maintenance free batteries. Unlike flooded batteries, they don’t need to be periodically filled with distilled water since they work on the oxygen recombination principle and never get dry.