Experimental and numerical investigation of heat transfer in Li‐ion battery pack of a hoverboard

Abstract

Summary Li‐ion cells are used for energy storage and conversion in electric vehicles and a variety of consumer devices such as hoverboards. Performance and safety of such devices are severely affected by overheating of Li‐ion cells in aggressive operating conditions. Multiple recent fires and accidents in hoverboards are known to have originated in the battery pack of the hoverboard. While thermal analysis and measurements have been carried out extensively on large battery packs for electric vehicles, there is relatively lesser research on smaller devices such as hoverboards, where the extremely limited thermal management design space and the critical importance of user safety result in severe thermal management challenges. This paper presents experimental measurements and numerical analysis of a novel approach for thermal management of the battery pack of a hoverboard. Measurements indicate that temperature rise in cells in the pack can be as large as 30°C at 4C discharge rate, which, although unlikely to be a standard discharge rate, may result from a malfunction or accident. A novel thermal management approach is investigated, wherein careful utilization of air flow generated by hoverboard motion is shown to result in significant temperature reduction. Measurements also indicate the key role of the metal housing around the battery pack in thermal management. Measurements are found to be in good agreement with finite element simulations, which indicate that the battery pack can be cooled as effectively in presence of a perforated metal casing as without the casing at all. Experimental data and simulation model presented here offer critical insights into the design of hoverboard thermal management and may result in safer, high performance hoverboard battery packs.

An improved electrothermal‐coupled model for the temperature estimation of an air‐cooled battery pack

“…Because the heat transfer model of the pack was related to the flow field, Sun et al employed the CFD method for the simulation of the flow field and the calculation of the heat transfer. Prasad et al studied the heat exchange in a pack used in a hoverboard with the CFD method. However, Prasad assumed the heat production rate in each cell to be constant and ignored the effect of current distribution in the pack on heat generation.…”

“…However, the proposed thermal model based on the battery resistance still has insufficiencies. Some research regarded cell resistance to only be affected by the SOC or the temperature, and some even considered that the resistance was constant . In practice, there are obvious prediction errors if the thermal models based on the battery resistance do not fully covers the effects of the electrical and thermal parameters on the resistance.…”

“…In practice, there are obvious prediction errors if the thermal models based on the battery resistance do not fully covers the effects of the electrical and thermal parameters on the resistance. Moreover, in the existing literature on the thermal model of the pack, the influence of the temperature distribution in the pack on the branch current is not considered, leading to an error in calculating the branch current. Encouraged by the study gap mentioned above, this paper builds a new electrothermal model to improve the temperature prediction precision of an air‐cooled pack.…”

“…Some research regarded cell resistance to only be affected by the SOC 31 or the temperature, 25 and some even considered that the resistance was constant. 16,29,32 In practice, there are obvious prediction errors if the thermal models based on the battery resistance do not fully covers the effects of the electrical and thermal parameters on the resistance. Moreover, in the existing literature on the thermal model of the pack, [24][25][26][27][29][30][31][32][33] the influence of the temperature distribution in the pack on the branch current is not considered, leading to an error in calculating the branch current.…”

“…The model includes the effect of the SOC and cell temperature on the resistance and current distribution in the pack (taking the inconsistent branch currents into consideration). Compared with the available thermal models, [18][19][20]25,27,[29][30][31][32] this paper has four main contributions. First, this work experimentally examines the effects of the cells' temperature and SOC on the ohmic and polarization resistances and the influences of the cells' SOC on the entropy coefficient, and the response surface model (RSM) expressed by the polynomial is used to establish their nonlinear internal relationships.…”