For lithium batteries, there are currently two main types of cells, namely 18650 and 21700 respectively.
21700 cell battery is the model of cylindrical battery, specifically speaking: “21” means that the outer diameter of the cylindrical battery is 21mm while “700” means the height of the cylindrical battery is 70.0mm.
As for 21700 cell battery, it is a new battery model developed to adapt to the requirement for longer mileage and to improve the effective utilization rate of vehicle battery space. Of the same material, 21700 cell battery can have 35% higher capacity compared with common 18650 cell cylindrical lithium battery.
The main differences between these 2 cell batteries are as follow:
1) Battery cell capacity has increased by 35%. Take the 21700 battery produced by Tesla as an example. After switching from 18650 cell model to 21700 cell model, the single battery capacity can reach 3~4.8Ah, greatly increasing by 35%.
2)The energy density of the battery system has increases by about 20%. According to the data disclosed by Tesla, the early energy density of 18650 cell battery system was about 250Wh/kg, while that of the 21700 cell battery system was about 300Wh/kg. The volume energy density of 21700 cell battery is nearly 20% higher than that of the original 18650 cell battery.
3)The weight of the system is expected to fall by about 10%. The overall volume of 21700 cell battery is greater than 18650 cell battery’s. With the increase of the monomer capacity, the monomer energy density is higher, so the number of batteries required under the same energy can be reduced by about 1/3, which reduces the difficulty of system management and also reduces the number of metal structural components and electrical components used in the battery pack, and further reduces the weight of the battery. Samsung SDI switched to a new 21700 cell battery, and found that the system weighs 10 percent less than the current battery’s.
Beside maintaining the high reliability and stable performance of the 18650 cell battery, the 21700 cell battery has been greatly improved compared with the 18650 cell battery in all aspects.
In addition, compared with other cell battery models, 21700 cell battery is similar to 18650 cell battery in terms of battery raw material selection, production process and technical process. Therefore, most of the production line of 18650 cell battery can be compatible with that of 21700 cell battery.
As for BeeCool models, Bee Pathfinder/Bee Pathfinder Step-thru/Bee Challenger has 21700 cell battery while Bee Adventurer/Bee Explorer/Bee Rambler has 18650 cell battery.
Bee Pathfinder Step-Thru
Foldable Ebike Cargo Trailer
Front Mounted Basket for Bee Adventurer & Explorer