Design and assembly lithium-ion NMC 18650 battery pack 11.1V 7.8Ah as a power bank

Thin and portable devices need energy storage, which also has high portability, such as batteries. It aims to support the mobility of its users. But the battery has a limited capacity. An external power source, such as a power bank, can be used to solve the issue. This research aims to assemble an 11.1 V 7.8 Ah battery pack from NMC 18650 battery cells as a power bank. The results of testing the battery pack at a current of 0.5 C obtained a discharge capacity of 7.5139 Ah, 96.33% of the theoretical capacity. This slight loss is possibly due to the current being used being large enough to cause some of the energy to be lost into heat energy. When the battery pack is used as a power bank by adding a USB DC-DC converter step down, there is a 3.7 % power loss from the supplied 7.04 W. This battery has theoretically 86 Wh, which can be used as a power bank for up to 12 hours.