Battery Performance Tests

After completing the first fully-functional battery module in June 2019, we could finally run different test scenarios to evaluate our preliminary design. After some additional modifications of our test module and extensive preparations for a proper testbed integration and data logging, we were provided a 100 A battery pack tester along with a climate chamber at the Institute for Power Electronics and Electrical Drives (ISEA). Our battery pack is equipped with an integrated PCM-cooling and a battery management system based on the open-source foxbms, which communicates through a CAN-interface and is connected to our control software. The BMS records voltage, current and temperature data in a frequency of 10 Hz. 12 voltage sensing lines are connected to the 12 serial connected cell blocks of 5 parallel cells each. We constantly measure 6 pack temperatures that cover corner cells, edge cells and cells located in the middle at both cell side (through the PCM) and negative pole. Additionally, the ambient temperature is tracked. For a precise current measurement, we extended our test battery with an IVT-S shunt-based current sensor that was sponsored by Isabellenhütte. It further tracks battery contactors and fuse voltages that are considered in additional safety checkups. More information of the battery pack construction can be found in our previous post. In this post, we want to present and discuss our test results.

Four scenarios were tested where the first three comprise tests of the full module and the forth is considering the emergency case with a single cell being tested. For all scenarios, climate chamber and battery were pre-conditioned to an initial temperature of 16 °C while the climate control remained deactivated during the test runs in order to avoid active cooling.


1. Fully electric profile – the original design profile comprising a fully electric start, climbing to 1000 m height and a subsequent cruise flight under pessimistic full-load conditions. Cruise flight is continued until any cutoff criterion (60 °C / 2.9 V) is reached.

StartClimbCruise
Aerodynamic
[kW]
46.140.59.8
Shaft
[kW]
68.652.211.2
Electric
[kW]
85.7565.2514
Performance Padding*
[kW]
94.3368.5114.7
Submodule
[kW]
3.932.8540.613
Duration / Limit90 s300 sCutoff limit reached
Climb Rate
[m/s]
4.73.40

Plots and results can be found here:

Electric Profile Battery Test Results


2. Reduced electric profile – electric profile with reduced climbing rate. Climbing was aborted at a measured maximum temperature of 58 °C after which a cruise flight is performed until a minimum cell voltage 2.9 V is reached.

StartClimbCruise
Aerodynamic
[kW]
46.129.59.8
Shaft
[kW]
68.638.0311.2
Electric
[kW]
85.7547.614
Performance Padding*
[kW]
94.335014.7
Submodule
[kW]
3.932.080.613
Duration / Limit90 s58 °C2.9 V
Climb Rate
[m/s]
4.72.40

Plots and results can be found here:

Reduced Electric Profile Battery Test Results


3. REX profile – hybrid-electric flight profile with continuous range-extender electric power of 25 kW. Climb phase is continued until any cutoff criterion (60 °C / 2.9 V) is reached.

StartClimbCruise
Aerodynamic
[kW]
46.140.5Only REX
Shaft
[kW]
68.652.2
Electric
[kW]
85.7565.25
Performance Padding*
[kW]
94.3368.51
Submodule
[kW]
2.891.81
Duration / Limit90 sCutoff limit reached
Climb Rate
[m/s]
4.73.40

Plots and results can be found here:

REX Profile Battery Test Results


4. Emergency profile – worst-case scenario simulating a battery pack failure during start tested on one cell. The redundant (parallel) battery pack must provide power for both engines and allow for a safe return. Start phase is shortened to the actual demand of 35 s and climb phase designed for reaching a safe flight altitude. Cutoff criteria are extended to 80 °C / 2.6 V.

StartClimbCruise
Aerodynamic
[kW]
46.1 9.8
Shaft
[kW]
68.6 11.2
Electric
[kW]
85.75 14
Performance Padding*
[kW]
94.336014.7
Cell
[W]
13183.320.4
Duration / Limit35 s160 s2.6 V
Climb Rate
[m/s]
4.7~ 30

Plots and results can be found here:

Emergency Profile Battery Test Results


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