Nigel S. Diones, Wynken Myrrh A. Gelito, Marc Julian M. Jamerlan (March 2012)
Philippine Science High School Western Visayas Campus – Department of Science and Technology (DOST-PSHS WVC), Brgy. Bito-on, Jaro, Iloilo City 5000, Philippines
ABSTRACT
An estimation of 73.6% of Filipinos has a cellular phone. Indeed over the years, the cellular phone has evolved to become an essential in the lives of many Filipinos sending more or less important messages to and for users. Cellular phones are powered by a secondary battery and the lithium-ion has become the favored choice of manufacturers all over the worlds due to its lower rate of increase in internal resistance compared with that of the nickel-cadmium, another suitable secondary battery. Overcharge is an occurrence when a secondary battery’s capacity has already been replaced yet is still in charge. During overcharge, lithium ions travel between two electrodes but without making actual contact thereby increasing the internal resistance. This study determined the difference in the internal resistance between an overcharged, and a normal-charged lithium-ion cellular phone battery. Specifically, internal resistance of overcharged and normal-charged lithium-ion cellular batteries were measured after a total of 60 cycles of 3 sets for 2 groups: 60 minutes and 240 minutes. The internal resistance after 60 cycles under 60 minutes group averaged to 10.30 ± 0.03 MΩ whole it averaged 10.39 ± 0.01 MΩ under the 240 minutes group.