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Nominal Voltage & Capacity of Lithium Ion Batteries

A cell is an Electro-chemical reaction which is housed in a mechanical structure. Usually, the commonly available cells you find, like alkaline cells are called by their mechanical structure – AA, AAA, D size batteries are found in most stores today. Sometimes, they are referred to by their nominal voltage, for example you go to the store and say that you’re looking for a 9 Volt battery, the attendant knows exactly what you’re talking about.

You would have noticed that I’m using the terms cell and battery interchangeably. This is technically incorrect, but still used in today’s communication. The difference between the two is that a battery comprises of two or more cells.

Let’s get back to the first experiment. Take a cell lying around in your house and pay attention to a few key parameters listed on the packaging of the cell. For example, pick a AA cell to see if the packaging says what the nominal voltage is, what about capacity in Ampere-hours? Duracell markets its AA cells as long lasting, is their capacity higher than the unbranded AA cells available, or is it just a marketing statement?

Here are some 9V cells, you can see how the nominal voltage and capacity varies with manufacturer and chemistry. Try to generate a similar table for cells you find around the house or in store to see the variance.

600mAh • 7.4VLithiumTenergy (silver, black base)
550mAh • 7.4VLithiumMaximal Power
300mAh • 8.4VNiMH (LSD)Maha Powerex (MHR84VP)
300mAh • 8.4VNiMH (LSD)Ansmann Energy
280mAh • 8.4VNiMH (LSD)EBL
250mAh • 8.4VNiMHTenergy 10001 (cyan color)
230mAh • 9.6VNiMH (LSD)Maha Powerex (MHR9VP)
230mAh • 9.6VNiMHMaha Powerex (MH-96V230)
200mAh • 8.4VNiMHTenergy Premium 10005 (white/red/blue)
150mAh • 7.2VNiMHEnergizer e2

​Ref: Michael Blue Jay

Nominal voltage is the standard voltage by which a cell is referred to. The actual voltage of the cell will vary around its nominal value. For example, a 3.7V nominal cell tells you that the voltage of the cell will be between 2.8V to 4.2V.

Capacity of a cell is usually measured in Ah. This represents the amount of charge the cell can hold. So a 5Ah cell, when fully charged holds 5Ah of charge, when charged half way holds 2.5Ah of charge.

With this experiment, you were introduced to two important parameters of cells which is nominal voltage and capacity​, understanding both of which is essential to understanding battery technology.

Silicon Anode

The Anode, an integral part of a Lithium-ion cell is one of the two electrodes. Let’s imagine that you are looking at an anode at a distance. What you will see is a metal foil, on which there is a black looking substance attached on top. Anode of a Lithium-ion cell (Reference: Bruno Vanzieleghem, Energy...
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Complications in voltage sensing of Lithium ion batteries

The concept of Kelvin sensing is explained below and why it is useful in battery voltage sensing. A current carrying conductor drops voltage across it, and in battery packs this current can be really high at times, which means that the voltage dropped will also be higher. The voltage sensing circuitry is usually far away...
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The difference between Alkaline and Lithium Cells

The Alkaline battery gets its name because it has an alkaline electrolyte of potassium hydroxide, instead of the acidic ammonium chloride or zinc chloride electrolyte of zinc-carbon batteries. Above, you see pictures of two types of cells that Panasonic makes. The ones on the top are AA type Alkaline cells. The ones on the bottom are AA type Zinc Carbon cells. Alkaline...
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4 Responses
  1. Prasanna Dakhore

    Why some mobile phones have LiPo Lithium polymer battery. What significance it holds considering the operation of the mobile phone

  2. Mahesh Padmanabh

    From my understanding Nominal voltage is the average of sums of voltage recorded during a charge and discharge cycle. Typically conducted using a low current of the order C/20 or so.

  3. akshay

    This may not always lead to the right result. For example – if we were to only take 2 points on the curve (max 4.2V and min 2.8V), then with this method the calculation would lead to 3.5V for a 3.7V nominal cell.

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