Authored By: Bernard Ang, Product Marketing Manager – Keysight Technologies

In today’s electronics applications, batteries power nearly all of our portable electronic devices. Batteries also serve as emergency power backup systems on large premises. And all-electric vehicles (EV) use large cascading battery packs to meet the expected power for the required performance. Battery packs need the required specific power (W/kg) to be able to dispense enough current to achieve the electric vehicle speed performance. They also need the required specific energy (Wh/kg) to achieve longer runtime or travel range.

Why Is It Important to Monitor Battery Temperature?

Most rechargeable batteries today are lithium ion and have an operating range between 15°C and 35°C at which their full performance and capacity kicks in.

• If the battery and its ambient temperature is below 15°C, you may experience sluggish electrochemical reactions within the battery and, as a result, lower battery performance and reduced charge capacity.
• If the battery or battery pack operates above 35°C in ambient temperature, battery degradation can accelerate over time. As a result, you may notice shorter battery life, non-uniform aging due to thermal gradients, greater exposure to safety issues and higher lifecycle costs. At extremely hot temperatures, batteries can break down and cause leakage, smoke, fire and even explosions.

The power map chart below shows the power limits of your lithium-ion battery or battery packs across the temperature range. The range between 15 °C and 35 °C is the optimum operating temperature range for the batteries to achieve full performance. The temperature range is also the most efficient, reliable, and safe range for battery operation.

Figure 1. Power map chart shows the power limits of your battery or battery pack across temperature range

(Source: Kandler Smith, NREL Milestone Report, 2008)

When to Use a Data Acquisition (DAQ) System for Monitoring Battery Temperature

A data acquisition (DAQ) system is one of the most versatile instruments to measure the temperature of physical objects or multiple objects. A DAQ system monitors temperature at multiple points in a product’s battery system. Typically, you initially test functional design blocks independently, and then you test sub-integrated design blocks during a product design and development stage. Testing for lab battery packs and systems occurs during an early product design cycle using several common R&D lab instruments.

A DAQ system can be used to monitor temperature at multiple points in a product’s battery system. Charge the battery system with a DC power supply and use a DC electronic load to discharge the battery system. Figure 2 below shows a common lab setup using a DAQ system. 

If you happen to own a bidirectional DC power supply that can source and sink current, then you can replace the separate DC power supply and DC electronic load with a bidirectional DC power supply.

Figure 2. Lab test setup for product battery system test using a DAQ, DC Power Supply, and DC electronic load

Using Keysight’s PathWave BenchVue software application, you can quickly set up and execute tests and get results faster. The application’s test flow feature allows you to build automated tests and reduces test development time significantly. The test flow feature also enables the simple sequencing of instrument settings and measurements, and combines multiple instruments to help you create your own automated test.

PathWave BenchVue software allows you to:

• Test the battery management system in your devices by varying the charging sources and discharging the electronic load while monitoring the temperature and behaviour of your battery system.
• Perform multiple temperature point measurements to evaluate cell-to-cell temperature variations.
• Set alarm triggers to monitor temperature, voltages or currents if they go above or below acceptable limits.

When to Use a Specialised Battery Test System for Monitoring Battery Temperature

Performing quick workarounds on bench test instruments may serve you well for quick troubleshooting and verifying your battery system design. However, when you need a dedicated and well-supported specialised battery test system, Keysight’s Scienlab SL-1000 series provides reliable and precise testing of battery systems whether they are in the cell, module or at the pack level. Figure 3 below shows how Keysight Scienlab battery test systems are scalable from individual stand-alone solutions, to fully integrated test systems and ready-to-use test laboratories.

Figure 3. Keysight Scienlab battery test system

The Scienlab SL-1000 series battery test system is scalable up to 1000 V, ± 2400 A and ± 360 kW. The battery test system is suitable for various energy storage applications ranging from automobile transportation, to industrial and other large on-premise use cases.

The Keysight Scienlab SL-1000 series battery test system offers many features that make it a standout in the market. The system comes with integrated test environments for your device under test (DUT) such as temperature and climate chambers, conditioning for your DUT and standardised contacting systems and integration to your DUT. There are also built-in safety and security mechanisms to help you avoid potentially hazardous situations.

Summary

Monitoring battery temperature occurs throughout the battery system’s product lifecycle. During the early stages of the product lifecycle, engineers can quickly troubleshoot and validate their battery system designs with bench instruments such as a DAQ, in conjunction  with a current sourcing and sinking DC power supply. During the characterisation and qualification stages of the product lifecycles, the Keysight Scienlab battery test solution becomes invaluable to you to ensure a precise and volume scalable test solution.

To learn more about the DAQ system for temperature measurements, visit https://www.keysight.com/my/en/products/modular/data-acquisition-daq.html, and to learn more about DC power supplies, visit https://www.keysight.com/my/en/products/dc-power-supplies.html.

For more information on the Keysight Scienlab battery test system, visit https://www.keysight.com/my/en/products/hev-ev-grid-emulators-and-test-systems/scienlab-battery-test-systems.html.

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