Determine How Many Cells In A Battery Pack

Working with batteries and battery packs is sometimes an overwhelming task if your new to it. As a blogger and battery store owner, I get alot of question about batteries. Such as, how many cells in a battery, comes up frequently. How many cells do I need to make a battery pack with a certain voltage. You get the point. Check out the video below to see me explain it.

WARNING

Math Ahead!! Run for the hills if you hate it.

Math For Cells In A Battery

The math is actually not that difficult. In fact is only a simple division problem. Lets do a couple examples with the following formula. Use the tables below to get the voltage and cells chemistries used in your battery packs.

Battery Voltage / Cell Chemistry Voltage = Number of Cells

Cordless Phone Battery: 3.6V Ni-CD Battery / 1.2V Ni-CD voltage = 3 Cells
Airsoft Battery: 9.6V Ni-MH Battery / 1.2V Ni-MH voltage = 8 Cells
Laptop Battery: 11.1V Li-Ion Battery / 3.6V Li-Ion voltage = 3 Cells (Actually 6 cells) this is a series-parallel configuration.

I will be explaining in an upcoming post how to determine series-parallel vs series configurations. When to use them and how they work.

Device Cell Orientations and Chemistry Voltages

The table below will help guide you with common battery pack orientations. It can also be used to help you build custom battery packs for your do it yourself project. You may decide that you need a similar pack and need to know how it is constructed. If I have missed any, use the comments to ask me how its built. I would be happy to explain any configuration.

Common Device
Amount of Cells
(Depends on Voltage)
Cells Used
Cell Configuration
Airsoft Battery
6 – 12
SubC
Series
Airsoft Lithium Battery
3 – 6
Li-Polymer Packs
Series or Series-Parallel
Cordless Phone
2 – 4
AA, AAA, 2/3A, 4/5A
Series
Laptop (External)
6 – 12
18650
Series-Parallel
Laptop (Internal)
6 – 12
Li-Polymer Packs
Series-Parallel
Power Tool Battery
7 – 12
SubC
Series

 

Common Chemistries
Cell Voltage (Nominal)
Alkaline
1.5V
Ni-CD (Nickel Cadmium)
1.2V
Ni-MH (Nickel Metal Hydride)
1.2V
LiFePO4 (Lithium Phosphate)
3.2V
Li-Ion (Lithium Ion)
3.6V / 3.7V
Lithium (Primary)
3.0V
Silver Oxide
1.55V

 

Still need more information on battery chemistries. A simple google search will find you everything you need but I actually like this article from Battery University. Whats the Best Battery, its explains the advantages and disadvantages of battery chemistries, their charge and discharge characteristics and best suggested application.

4 thoughts on “Determine How Many Cells In A Battery Pack”

  • how to figure out if a battery is NICD or Li, if no label? . size is app. 164mm x 18mm. voltage on multimeter reads app. 3.9V. (this is being used in a spin scrubber)

    Reply
    • The voltage right away suggests that it's possibly some kind of lithium. It's not LiFePO4 because those are in the 3.2 - 3.4 V range. So it must be some type of Lithium Ion or Polymer. However, the measurements, specifically the length is not a typical length of lithium. This could be several batteries in series add the voltages up to 3.9V which then would not be a lithium battery. The diameter is a normal lithium size though. In conclusion, it appears that you have a battery that is constructed on several cells in series making the battery pack possibly Ni-CD or Ni-MH. There is probably a wrap holding the cells together and making it a singular battery pack.

      To be sure I would need to see pictures. You can send them to our emails sales (at) batteriesinaflash.com

      Reply
  • I've been trying to understand battery instructions and diagrams; I'm an Ironworker Contractor not an electrician of any sort. As a home project, I'm building a solar generator with 8 Deep Cycle AGM Sealed Lead Acid 27 Batteries charged by 6 - 160 watt solar panels. I would really appreciate some help with how best to wire the 8, 12 volt batteries into a workable 24 volt battery pack. The more I research online the more confused I get; will you please help me with this?

    Reply
    • Gordon, you will make 4 groups of batteries in series by connecting two batteries positive to negative. Using a multimeter you can test that the batteries now give you 24 volts. You will do that for all four groups. Then with those 4 groups, you connect all the positives together on the side, and on the opposite side connect all the negatives together. Once you do this you can check the group and see that you will still have 24 volts nut now that amperage is all added together.

      You can review this page for diagrams to assist you. How to wire your batteries is series parallel

      Reply
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