All-electric or hybrid electric aircrafts, wherein batteries are key components, are promising to reduce CO2 emissions. Knowing a battery’s behavior over a broad range of different conditions, mainly temperature and load changes, is crucial for efficient usage of a battery, especially in aircrafts. Therefore, a model that can predict the battery behavior in relation to electric airplanes was developed. For this contribution, a model using an equivalent circuit with a voltage source, one R and two RC parts was used to have a good trade-off between accuracy and computation time [1]. Due to the short computation time, it is possible to combine the model with a whole aircraft model or even integrate it into the battery management system. The model was done for three different commercial lithium ion batteries planned for aviation applications: The 20 Ah HP602030 LFP cylindrical cell was chosen due to good thermal stability and safety of LFP [2][3] which is crucial for aviation.The 10 Ah HE 341440 NCA cylindrical cell was chosen since NCA has a high specific energy due to a high specific capacity and high voltage vs lithium [4]. This high specific energy leads to lower weight which is another important aspect for aviation.The 12 Ah SLPB065070180 NMC pouch cell was chosen, since NMC has a good trade-off between energy density, costs and safety [4]. The open circuit voltage (OCV) of each battery was determined by measuring a charging and discharging curve with low current of C/40. The medium of these two curves had a good accordance to galvanostatic intermittent titration technique measurements and therefore was assumed to correspond to the open circuit voltage over state of charge (SOC). The SOC is calculated by coulomb counting based on the usable capacity dependent on temperature and current. To calculate the resulting battery voltage at the current collectors, the OCV is reduced by voltage drops due to the equivalent circuit resistances and capacitances using typical equations for electrical circuits. These resistance and capacitance are dependent on current, temperature and SOC. To determine these dependencies, cycles at different currents and temperatures were performed. To keep temperature and humidity constant, the batteries were placed in a climate chamber. The two main heat sources for batteries are considered in the simulation. Joule heat is calculated by power losses. The reversible heat is calculated with the entropic potential. Heat distribution is considered to be equal over the whole cell.Figure 1 shows the comparison of first simulation results with measured data of two NCA battery cells. The simulated data for 2 A is in between the two battery measurements. The comparison at 5 and 10 A shows a good agreement at high SOC. At low SOCs, there is some deviation which is tolerable since the batteries will only be discharged up to approximately 80% SOC in the aircraft due to safety considerations. Additionally, the 5 and 10 A simulation values are below the measured values which means the real battery would...
Stopping climate change and global temperature rise needs a determined course of action in several technology fields and the development of ZERO-CO2 aircrafts and low emission battery-ICE aircrafts, as well. Batteries in hybrid-electric or fully-electric aircrafts are an option to decrease emissions. The battery requirements for the aviation sector regarding specific energy, energy density and safety are high. Lithium-ion batteries are today the only commercially available technology to meet these requirements, but adequate technology readiness is only proven for the automobile sector while TRL levels 8 and 9 for implementation readiness of batteries in the aviation sector is still ongoing. A crucial aspect for aviation applications is the operation behavior in high altitude including low temperature, wide humidity ranges and especially low pressure. There is little published information available on the effects of low pressure on battery performance. Therefore, different commercially available lithium-ion batteries were tested from atmospheric pressure down to 250 hPa, which corresponds to a flight altitude up to 10,000 m, according to the International Standard Atmosphere (ISA). Since NMC and NCA cathode materials are promising for aviation due to their high specific energy, and LFP cells are promising because of their high safety, the following batteries were selected: 20 Ah HP602030 LFP cylindrical cell (EAS Batteries GmbH, GER). 10 Ah HE 341440 NCA cylindrical cell (EAS Batteries GmbH, GER). 12 Ah SLPB065070180 NMC pouch cell (Kokam Co. Ltd., KOR) To examine the influence of pressure on the battery behavior, constant current discharge tests at 1C 0.5C and 2C rates as well as impedance measurements in 10% SOC steps were performed in a climate controlled low-pressure chamber. The batteries were operated under different temperatures and in controlled low pressure. The pressure was first set to atmospheric pressure as a reference and then lowered to 750 hPa, 500 hPa and 250 hPa. To further examine altitude influences, current cycles and impedance spectroscopy were performed at different temperature and humidity values. The behavior of the cylindrical cells showed hardly any pressure dependency, while the examined pouch cell’s behavior did show a pressure dependency. All batteries showed strong temperature dependency but hardly any humidity dependency. In this presentation the influence of pressure, temperature and humidity on voltage, capacity, resistance and impedance of the afore mentioned batteries will be discussed. The batteries are compared regarding their aviation applicability with special respect to low pressure. The parameters for each environmental condition can then be used to parameterize a battery model suitable for aviation applications.
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