Sinusoidal ripple-current charging has previously been reported to increase both charging efficiency and energy efficiency and decrease charging time when used to charge lithium-ion battery cells. In this paper, we show that no such effect exists in lithium-ion battery cells, based on an experimental study of large-size prismatic cells. Additionally, we use a physics-based model to show that no such effect should exist, based on the underlying electrochemical principles.

In the majority of applications using lithium-ion batteries, batteries are exposed to some harmonic content apart from the main charging/discharging current. The understanding of the effects that alternating currents have on batteries requires specific characterization methods and accurate measurement equipment. The lack of commercial battery testers with high alternating current capability simultaneously to the ability of operating at frequencies above 200 Hz, led to the design of the presented experimental setup. Additionally, the experimental setup expands the state-of-the-art of lithium-ion batteries testers by incorporating relevant lithium-ion battery cell characterization routines, namely hybrid pulse power current, incremental capacity analysis and galvanic intermittent titration technique. In this paper the hardware and the measurement capabilities of the experimental setup are presented. Moreover, the measurements errors due to the setup’s instruments were analysed to ensure lithium-ion batteries cell characterization quality. Finally, this paper presents preliminary results of capacity fade tests where 28 Ah cells were cycled with and without the injection of 21 A alternating at 1 kHz. Up to 300 cycles, no significant fade in cell capacity may be measured, meaning that alternating currents may not be as harmful for lithium-ion batteries as considered so far.

For safety and longevity reasons, in subzero temperatures, lithium-ion batteries can only be charged after precommissioning their temperature. Therefore, in such conditions fast charging depends on fast heating. Recently, the injection of AC currents into lithium-ion batteries has been reported as a technique with potential to decrease heating time. This paper proposes a method based on a multi-objective algorithm for DC-DC converter design using transformerless resonant filters. The method enables the DC-DC converters to produce magnified AC current in addition to the DC current. Using the proposed design method, a topological survey of DC-DC converters with magnified AC current capability composed of either half-or full-bridge switch arrangements is carried out. In the presented experimental setup, it is demonstrated that by using an LCL circuit with specific component values and a full-bridge switch arrangement, magnifications of up to 15.7 may be reached. Further, by matching the switching frequency with the frequency where the LCL and the battery resonate, for the same injected AC current, the current flowing in the semiconductors and the switching frequency could be reduced. This allowed a loss reduction in the semiconductors of up to 75%, when compared with an equivalent DC-DC converter enabled to produce a nonmagnified AC current.

Batteries in energy storage systems are exposed to electrical noise, such as alternating current (AC) harmonics. While there have been many studies investigating whether Lithium-ion batteries are affected by AC harmonics, such studies on Nickel Metal Hydride (NiMH) batteries are scarce. In this study a 10 Ah, 12 V NiMH battery was tested with three different harmonic current frequency overlays during a single charge/discharge cycle: 50 Hz, 100 Hz, and 1000 Hz. No effect on battery internal temperature or gas pressure was found, indicating that NiMH battery aging is not affected by the tested harmonic AC frequencies. This can reduce the cost of energy storage systems, as no extra filters are needed to safeguard the batteries. Instead, the capacitive properties of the batteries give the possibility to use the battery bank itself as a high pass filter, further reducing system complexity and cost.