Using Voltaplex to Find the Best Lithium-ion Battery

Finding the right lithium-ion battery is difficult, as there are so many variations and specifications. Using a new tool like Voltaplex Filters lets you easily filter, sort, and browse thousands of lithium-ion cells and battery pack configurations. Filters include or min. and max. capacity, configuration, cathode type, and so on.

Use it here: Browse and filter lithium-ion cells

Step 1: Know the Different Type of Cells

There are several flavors of lithium-ion cells available today, each with their specific advantages and disadvantages.

The first two are similar:

1. Lithium Polymer (Pouch) cells have a soft outer-shell and are very slightly flexible. Cells like these are often used to power drones and UAVs because of low-weight and high-discharge currents. Polymer cells are quickly reaching the energy density of cylindrical cells.

2. Lithium Prismaticcells, are very similar to polymer cells, except they have a hard outer shell. This makes them more modular, and better suited for large applications like electric vehicles.

Then, there is the

3. Coin or button cell. These are small batteries, often found in watches or other wearable or medical devices. Recent advances have created the LIR or lithium-ion rechargeable coin cells. These can be charged and recharged which gives them an advantage in some devices.

Finally, there are the cylindrical batteries:

4. The 18650 battery is the most common, found in laptops, electric vehicles, vaporizers, and nearly anything. 18650 batteries are probably the most market-ready, with the highest-energy densities and lowest cost per kilowatt hour. They are also generally safe and crush-proof, surrounded by a thick cylindrical steel casing.

5. The 21700 battery is the up-and-coming cylindrical cell format that some predict will replace 18650 batteries, or at least take a good share of the market. They boast an even better cost-per-kilowatt hour as the increase in size is more efficient.

6. Finally, there are the other sizes, like 14500, or 26500 . These sizes are not as common and are used in more custom applications. Frequently LiFePO4 cells will use non-standard sizing or larger format cylindrical cells.

Step 2: Capacity, Current, and Voltage

Typically, the three most important attributes for any lithium-ion cell are

Maximum capacity
Maximum continuous discharge current
Nominal voltage

The capacity of the cells tells you how much total energy it can hold. Capacity is measured in amp-hours (Ah). Typically, the bigger the cell, the more it can hold. Lithium-ion cell chemistries including cobalt like NMC can reach the highest capacities. In electric vehicles, capacity tells you roughly how far you can go on a single charge.

Range: 0 mAh to 200,000 mAh per cell

The current is how powerful your cell is, or how much electric charge can go across the surface per second. Current is measured in amperes (A). If you need an electric skateboard to go up a very steep gradient, current is what you should be focused on optimizing. Cells with higher currents (and less capacity) are typically the least expensive.

Range: 0 A to 440 A per cell

The voltage is sometimes called electric pressure and plays an important role in how energetic or powerful your device can become. It is measured in volts (V). Nearly all lithium-ion batteries are set to a nominal voltage of 3.6 or 3.7 V. Note that this is the mid-point between a charge voltage (often 4.2 V) and a discharge voltage (often ~3.0 V).

Range: 3.2 V to 3.8 V per cell

Step 3: Energy, Max

Energy is an important attribute that many think is overlooked, and shouldn't be. It maybe gives a more precise overview of the capability of a cell. The unit of energy is Watt-hours. It is a fundamental attribute; the ability to do work. The formula for watt-hours used in lithium-ion cells is:

(mAh) * (V) / 1000 = (Wh)

The range of lithium-ion cell energies is 0 to 640 Wh. From an LIR coin cell with 0.74 Wh to a large prismatic battery with 160 Wh.