非标准充放电循环测试简介：自定义电流分布

introduction

The battery in an electric vehicle discharges while accelerating and maintaining vehicle speed. When the vehicle is braked, the battery is recharged. The driving cycle can therefore reflect significant changes in battery discharge and charging, so that it is possible to observe amp-level current fluctuations. For example, the United States Advanced Battery Association (USABC) conducted a federal city driving schedule (FUDS) cycle test on electric vehicles, and then the results are shown in Figure 1 as a percentage of peak discharge power versus time. Negative percentage values ​​refer to the discharged state, while positive values ​​refer to the charged state.

The battery's cyclic charge and discharge (CCD) is a standard cycle test implemented by Gamry in the electrochemical energy package. We also have an application report explaining how to run a CCD with our electrochemical workstation. In this application report, a cyclic test of constant current, power or resistance is not sufficient. The test used here uses a preset current distribution to discharge the battery. This current distribution is designed to simulate the operating conditions that a battery faces during its life. Here we tested electric vehicles and driving cycles, such as the US Environmental Protection Agency (FBA) Urban Dynamometer Driving Schedule (UDDS), and associated battery charging and discharging.Although we have not tested real electric vehicle batteries, we show the results of a standard 18650 lithium-ion battery.

Finally, we showed how to create a Framework™ software script on your Reference™ 3000 or Interface™ 5000 to run various tests.

Battery specifications and installation

Using the loop in Figure 1, we created a preset current distribution as shown in Figure 2. This current distribution is scaled for our Interface 5000 electrochemical workstation. We run ten cycles in order to ensure that the electrolytic cell reaches the lower voltage limit.

Figure 1 FUDSUSABC-FUDS cycle test based on FUDS exhaust gas test c

(Source: http://www.uscar.org/guest/teams/12 )

Figure 2 Current distribution for the first 3600 seconds for battery discharge

Current scaled to a maximum of 5 amps to match the Interface 5000 electrochemical workstation

In addition to displaying non-standard cycle tests, we have used the built-in interfaces of the Interface 5000 and Reference 3000 electrochemical workstations to detect temperature monitoring [JB1]. Reference 3000 contains a typical K thermal coupling interface, as shown in Figure 3. On the Interface 5000, the temperature monitoring requires the auxiliary 5000 monitoring substrate, which is directly connected to the monitoring interface on the front panel.

 

The measured 18650 battery specifications are listed in Table 1. The interface of the instrument is marked in Figure 3. The connection is shown in Figure 4. An RTD element (Omega, RTD-1-F3141-60-T) for temperature monitoring is attached to the outer surface of the electrolytic cell. RTD components are connected via an Interface 5000 monitoring board (Gamry Instruments 990-00401). The monitoring board is an accessory that provides BNC connection to auxiliary channels through the front panel monitoring interface.

Table 1 battery specifications