**5. Conclusions**

This paper proposed a pulse charging technique using additional charging circuits for the quick charging of lithium-ion batteries. Pulse charging shortens the charging time, but may degrade the performance of the battery. Therefore, pulse charging should be able to be optionally required. However, conventional charging systems require both pulse chargers and CC–CV chargers. The proposed add-on pulse charging circuit was connected to the existing CC–CV charger, allowing pulse charging. This charging circuit had the advantage of being applicable not only to electric vehicles but also all applications that use batteries.

This paper presented the pulse charging circuit, experimental method and data analysis. Pulse charging technology was applied to 18650 cylindrical lithium ion batteries to analyze the experimental results. Pulse charge and CC charge experiments were performed in the constant current charge section of the battery. Through repeated experiments, the charging rate by pulse charging in fresh battery condition was similar to that of conventional CC charging.

However, as battery performance deteriorated, the charge speed increase of CC charging gradually decreased. On the other hand, the increase of the charging speed by pulse charge gradually increased. To neglect the effects of aging, pulse filling was first performed. Therefore, pulse charging is more effective when battery performance degrades. In a real battery, its life is much longer than a fresh battery. Thus, in applications where charge/discharge frequently occurs, such as in electric vehicles, the proposed pulse charging rather than CC charging has a long-term advantage. In particular, the existing charging infrastructure was constructed using CC–CV chargers. Instead of installing a separate pulse charger for fast charging, using the proposed charger is expected to reduce overall costs.

In the future, we will compare pulse charging and CC charging characteristics while continuing to degrade battery performance.

**Author Contributions:** Conceptualization, B.K., and M.K.; methodology, validation, analysis, and analyzed the data, B.K., and J.K.; writing—original draft, B.K.; Writing—review and editing, supervision, and project administration, M.K., and J.K. All authors have read and agreed to the published version of the manuscript.

**Funding:** This study has been conducted with the support of the Ministry of Trade, Industry and Energy as "Future Growth Engine Business project (20003558)".

**Conflicts of Interest:** The authors declare no conflict of interest.
