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This paper presents the use of a second life battery pack in a smart grid-tied photovoltaic battery energy system. The system was developed for a single family household integrating a PV array, second life battery pack, grid back feeding, and plug-in hybrid electric vehicle charging station. The battery pack was assembled using retired vehicle traction batteries. The pack is configured with 9 cells in each parallel bank, 15 banks in series featuring 48V nominal and a 12kWh nominal capacity. Limited by the weakest bank in the pack, the second life battery pack has an accessible capacity of 10kWh, or 58% of its original condition. A battery management was developed to handle the bank-to-bank imbalance and ensure the safe operation of the battery pack. An energy management algorithm was established to optimize the energy harvest from PV while minimizing the grid dependence.

Optimizing the hardware design and control strategies of thermal management systems (TMS) in battery packs using large format pouch cells is a difficult but important problem due to the limited understanding of how internal temperature distributions impact the performance and lifetime of the pack. Understanding these impacts is difficult due to the greatly varying length and time scales between the coupled phenomena, causing the need for complex and computationally expensive models. Here, an experimental investigation is performed in which a set of fixed one-dimensional temperature distributions are applied across the face of a Nickel-Cobalt-Manganese (NCM) cathode lithium ion pouch cell in order to study the performance impacts. Effects on the open circuit voltage (OCV), Ohmic resistance, bulk discharge and charge resistance and instantaneous power are investigated.