Electric bike lithium battery 18650 battery types and assembly

Most electric bike lithium batteries are made with 18650 battery cells( size: 18mm-diameter * 65mm-height), with different shapes, different voltages and capacities upon different applications. 18650 battery has a variety of types.

Classified by electrolyte material

There are liquid lithium-ion batteries (LIB) and polymer lithium-ion batteries (PLB).

Classified by brands

Seen from the electric bicycle lithium-ion battery in the market, there are many lithium battery brands such as Samsung, Panasonic, Sony, LG, Sanyo, Battemen, and many Chinese lithium battery brands like BYD IT, BAK battery, LISHEN Battery, First battery etc.

Classified by capacity

Generally, we would see 2000mAh, 2200mAh, 2600mAh, 2900mAh, 3000mAh, 3200mAh, 3400mAh, 3500mAh etc.

Classified by the active materials

How do the battery cells be connected to build a big battery? How many cells do you need to build the battery?

Connect the battery cells in series or parallel could increase the battery voltage or get a higher capacity.

Take the 3.6V 3400mAh lithium-ion battery cells as a sample. Connection in series will increase the voltage, 4 series makes 4*3.6= 14.4V, 10 series makes 10*3.6= 36V, 13 series makes 13*3.6= 48V. Connection in parallel will gain a higher capacity. 4 battery cells or 4 groups of cells ( 10 cells in series) assemble in parallel would gain a 4*3400mAh= 13600mAh= 13.6Ah capacity.

So to make a 36V 13.6Ah lithium battery, you need 40 battery cells which are all 3.6V 3400mAh. And kindly noted that the voltage difference of each battery cell should be smaller than 0.05V, or it would affect the lifetime of the battery.

Some electric bikes need a 48V voltage to work with the 48V motor and controller that it should be13 battery cells in series. Then you need to confirm that how many battery cells are limited by the battery pack or battery box to assemble suitable battery groups in parallel.

Apart from electric bikes, 18650 battery are widely used in laptop, power bank, electric toys, and the connection method is same.