Agilent Technologies AN 372-2 user manual

Summary of the content on the page No. 1

Agilent AN 372-2
Battery Testing
Application Note
An electronic load can be used to discharge batteries of various
chemistries to determine actual capacity, capacity retention,
and internal impedance.

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Introduction Increasing demand for portable DC Whether testing batteries in R&D or power has risen from improvements production environments, the test in battery and motor design technol- requirements for each of the different ogy. More than ever before, portable battery types are basically the same. DC powered products have become Figure 1 shows a common test config- available in many diverse applications. uration. In general, the testing of a Rechargeable batteries appear in all battery involv

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Application Overview and Test Implementation 1 Seven standard test procedures are the specified minimum voltage called Rated Capacity used to verify certain electrical char- the “end of discharge voltage” (EODV). The principal measurement of a acteristics of secondary batteries: The EODV for nickel-cadmium batteries battery’s performance is its rated is typically 1.1 to 0.9 Volts. capacity. Capacity ratings are attained 1. Rated capacity in an accelerated test approximating 2. Capacity retentio

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Capacity varies with the rate of dis- Average and maximum capacities are Capacity Retention charge as shown in Figure 3. Testing obtained by putting the battery through This test characterizes how much of a for how discharge rate affects capacity five successive charge/discharge sta- fully charged battery’s capacity is is discussed later in more detail. bilizing cycles. The batteries are given retained over a long period of time Generally, lower discharge rates over five stabilizing cycles where

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The battery is given five stabilizing Impedance Test Effective Internal Impedance cycles in accordance with the previ- The battery must be fully charged as Battery impedance is dependent ously outlined procedure. outlined above. An AC current source on temperature, its state of charge, ( 1 kHz) is applied to the terminals of and the load frequency. The effective ~ Life Cycles 1 through 48 the battery. The AC current through internal impedance is lower for a fully 1. Charge 11 hours and the bat

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Many cells can be quick-charged at a One final test, called the “forced dis- Miscellaneous Tests rate up to C/3 in as little as 3 to 5 hours charge test,” determines the safety of In addition to the tests already men- instead of the standard 12 to 15 hours a battery under certain abusive con- tioned, there are also other miscella- at the C/10 rate. High rate charging ditions. This test is very dangerous neous tests performed on nickel- should be done under controlled con- because, during the tes

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Test Equipment Requirements From the various tests described The second alternative (Figure 7) shows so far, we can see some common that using a power supply may be more requirements for test equipment. All desirable because timed fast charge, the tests require a discharge cycle dump-timed charge, and forced dis- using a constant current. A constant charge tests all require a DC power discharge current cannot be attained source anyway. Additionally, a con- with a simple resistor because the stan

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Battery Testing with Agilent Electronic Loads Agilent Technologies Electronic bus so that time consuming discharge By internet, phone, or fax, get assistance with all your test and measurement needs. Loads are ideally suited for battery tests can be attended automatically. test applications. Their many features Agilent’s electronic loads truly provide Online Assistance make the test system easy to config- a “One Box” solution. www.agilent.com/find/assist ure and provide safe, reliable, and Phone