A Comparison of Bitrode's HRD and VRL/VRX Production Line Test Equipment
note number - hpd0001

HRD2000 and HRD3000

The HRD utilizes a fixed, water-cooled resistance load that is connected to the battery under test through an electronic switch (Figure I). The load is applied to the battery for a selectable period of time (typically two seconds) and the current produced is monitored during the test. If the current stays above a preset value for the duration of the test, the battery is considered good. If the current falls below the preset value, the battery is rejected.

FIGURE I



Since the resistance is fixed the amount of current drawn from the battery is unregulated and influenced by many factors, including:

• Battery capacity
• Battery State of Charge
• Battery Internal Resistance
• Terminal Resistance
• Voltage drop of the solid state switches

In addition the above, there are voltage differences caused by environmental and operating conditions which could affect the current delivered by a battery under test:

• Solid state switch voltage as a function of temperature
• Water cooled resistance change as a function of temperature
• Voltage drop in the water cooled cable as a function of temperature

These differences could yield varying results for the same battery produced on a different shift, different day or in a different plant.

Bitrode offers a range of bolt-in load elements that allow the tester to be somewhat tuned to match the capacity of the batteries being tested. The HRD is suitable for pass/fail testing on batteries of similar capacities and testing requirements.

VRL

The VRL utilizes a variable resistance load that is connected to the battery under test through an electronic switch. The load is applied to the battery for a selectable period of time and can be programmed to maintain either constant current or constant voltage during the test.

In constant current mode (Figure II) the battery current (as measured using a shunt) is controlled to a preset level. The battery is passed or rejected based on how low the terminal voltage drops during the test.

FIGURE II

In constant voltage mode (Figure III) the battery voltage is controlled to a preset level. The battery is passed or rejected based on how low the current drops during the test.

FIGURE III

Since the resistance is variable and controlled, the VRL can maintain constant current or voltage regardless of changes in terminal resistance, cable resistance, switch voltage differences, etc. This means that results do not vary from shift to shift, day to day or plant to plant.

It must be noted that the resistance range has upper and lower limits and the range of battery types to be tested should be specified when a VRL is ordered. The VRL provides greater flexibility by allowing the battery producer to create custom tests to match battery capacities and testing requirements.

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