Abstract
This article presents a test bench with variable temperature control of the individual cells connected in parallel. This allows to reconstruct arising temperature gradients in a battery module and to investigate their effects on the current distribution. The influence of additional contact resistances induced by the test bench is determined and minimized. The contact resistances are reduced from R Tab + = 81.18 μ Ω to R Tab + = 55.15 μ Ω at the positive respectively from R Tab − = 35.59 μ Ω to R Tab − = 28.2 μ Ω at the negative tab by mechanical and chemical treating. An increase of the contact resistance at the positive tab is prevented by air seal of the contact. The resistance of the load cable must not be arbitrarily small, as the cable is used as a shunt for current measurement. In order to investigate their impacts, measurements with two parallel-connected cells and different load cables with a resistance of R Cab + = 0.3 m Ω , R Cab + = 1.6 m Ω and R Cab + = 4.35 m Ω are conducted. A shift to lower current differences with decreasing cable resistance but qualitatively the same dynamic of the current distribution is found. An extended dual polarization model is introduced, considering the current distribution within the cells as well as the additional resistances induced by the test bench. The model shows a high correspondence to measurements with two parallel-connected cells, with a Root Mean Square Deviation (RMSD) of ξ RMSD = 0.083 A.
Highlights
Large-scale battery applications like electric vehicles (EV) have to meet high power and energy demands, which is mostly realized by the parallel-connection of lithium-ion cells, e.g., Tesla Model S (74p96s (The abbreviation xpys corresponds to a cell configuration with x cells in parallel and y cells in serial connection)), Tesla Model 3 (46p96s), VW eGolf (3p88s), Nissan Leaf (2p96s), BAIC EU260 (3p90s), Renault Zoe (2p96s) and Audi etron (4p108s) [1,2]
Caused by production-induced distributions of cell resistances and capacities [3,4], inhomogeneous cell currents arise within these parallel cell configurations [5], further leading to State of Charge (SoC) [6,7], Open Circuit Voltage (OCV) [8,9]
The OCV bending at low SoC led to a rapid voltage drop of cell one, which resulted in a current peak of cell two
Summary
Large-scale battery applications like electric vehicles (EV) have to meet high power and energy demands, which is mostly realized by the parallel-connection of lithium-ion cells, e.g., Tesla Model S (74p96s (The abbreviation xpys corresponds to a cell configuration with x cells in parallel and y cells in serial connection)), Tesla Model 3 (46p96s), VW eGolf (3p88s), Nissan Leaf (2p96s), BAIC EU260 (3p90s), Renault Zoe (2p96s) and Audi etron (4p108s) [1,2]. Both the formation of temperature gradients due to the current distribution and the impacts of design-induced temperature gradients in a battery module on the current distribution can be investigated. This simulation model takes into account the influences of the test bench on the current distribution and the parallel-connected cell layers within the cells.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
