18650 Li-Ion Cell Technology Information & Applied Scenarios (WIP*)

18650 Li-Ion Cell Technology Information & Applied Scenarios (WIP*)


Utilizing The Abundant 18650 Cell

Utilizing the energy storage capabilities of 18650 Li-ion cell batteries conjoined with solar cells; creates opportunities to supply affordable, customizable, & portable; DIY solar storage units. Specifically the 18650 cell “battery” has an abundance of functional & economic uses for powering DIY electrical devices. 18650 Li-Ion cells are found in old battery packs, laptops, cameras and other high powered electronic devices. Utilizing these cells in a conjoined configuration will boost the total amount of energy stored to run any electrical device. The more cells joined together; the more energy & milliampere-hours(mah) a device will have to operate. Solar panels used in conjunction will recharge the battery port back up to full capacity.

“Reusing 18650 cells promotes a recycle friendly activity.”

Preliminary Steps for choosing ideal cells

Connecting multiple 18650 cells together to create a larger battery requires preliminary steps to ensure the longevity and safety of each cell used. These steps will determine the statistics & performance of each cell. Knowing the specific voltage(V) and capacity(mah) of each cell is important to determine which cells are similar enough ideally work together. Grouping cells of similar voltage(V) and capacity(mah) for the project is ideal when considering performance and precision.

  • “Multimeter” or “voltmeter” can calculate voltage(V) between (+) & (-) points in the cell;
  • “Cell charger/discharger” will fully charge and & discharge a cell to calculate capacity(mah).

Initial Voltage Test

Once you Each cell has a positive(+) and negative(-) terminal

18650 Battery Size

Electrical Wiring Terminology

Series circuits: are sometimes referred to as current-coupled or daisy chain-coupled. The current in a series circuit goes through every component in the circuit. Therefore, all of the components in a series connection carry the same current. A series circuit has only one path in which its current can flow. Opening or breaking a series circuit at any point causes the entire circuit to “open” or stop operating.”

Parallel circuits: If two or more components are connected in parallel, they have the same difference of potential (voltage) across their ends. The potential differences across the components are the same in magnitude, and they also have identical polarities. The same voltage is applied to all circuit components connected in parallel. The total current is the sum of the currents through the individual components”

Wikipedia: https://en.wikipedia.org/wiki/Series_and_parallel_circuits

  • Connecting cells in “series” will increase your voltage output while the capacity(mah) will remain the same.

    “(Example): (3) 3.7V – 3200mah 18650 cells in series has an output of 11.1V @ 3200mah. – (3.7V)x(3)=11.7V & (3200mah)x(series ∞)=3200mah

  • Connecting cells in “paralell” will increase your the total capacity but voltage will remain the same.

    “(Example): (3) 3.7V – 3200mah 18650 cells in paralell has an output of 3.7V @ 9600mah. – (3.7V)x(parallel ∞)=3.7V & (3200mah)x(3)=9600mah

  • Connecting multiple groups of “series” cells in “paralell” will increase voltage and capacity at the same time.

    “(Example): 3 groups of (3) 3.7V – 3200mah 18650 cells in series & connected together in parallel has a total output of 11.1V @ 9600mah. – (3.7V)x(series 3)=11.1V & (3200mah)x(parallel 3)=9600mah

  • Cells in “series” operate like a chain; if one cell fails; the whole group will not work. However if you wire them in “parallel” each cell works as a team; if some fail; the whole array will still work but at less capacity(mah).
  • Wiring in “series/paralell” works by gathering multiple cell groups in “series” and connecting those groups in “paralell”. This allows everything to operate as separate groups in even if a group of cells in “series” fail. Wiring “series” grouped cells in “paralell” will allow current to flow past the failed group; to allow current to flow to the rest of the operating groups. In this case think of the grouped cells in “series” as an envelope and the whole connected groups in “paralell” as the container that holds all the grouped cells.

Watt(W): net unit of power

kwh: kilowatts per hour

mah: milliamps per hour

ah: amp hours

Volt(V): potential difference in energy



Ohms Law

V=I*R      I=V/R      R=V/I

Average Notable “18650” Voltage Reading Specs

4.2V @ Full Charge

3.7V @ Nominal Charge

(2.4V – 0V) @ N/A – 0 

Information Resources

https://secondlifestorage.com/ – “This Cell Database is a community-driven project to catalog pictures, datasheets, and other useful information for the various battery cells”

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