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Counters: Difference between Lithium Battery and EEPROM for Storing Data during Power Interruption

FAQ No. FAQ03185

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Question

What are the differences between using a lithium battery and EEPROM for storing Digital Timer and Counter data when a power interruption occurs?

Answer

What are the differences between using a lithium battery and EEPROM for storing Digital Timer and Counter data when a power interruption occurs?

Power-interruption memories are available for motor-type timers and electromagnetic counters using mechanical methods, and their counterparts are available for electronic Timers and counters using a lithium battery and EEPROM.

The main differences between the two methods are as follows: With a lithium battery, the internal control circuit and display circuit are constantly backed up by the power of a lithium battery, whereas with an EEPROM, the necessary data is written to EEPROM when the power is interrupted.

Because the lithium battery has a service life of approximately 10 years, the power-interruption memory function stops when the battery reaches the end of its lifetime. However, the other functions in the Timer or Counter can still be used just as they are. Also, though the lithium battery cannot be replaced in Timers and Counters for which the replacement procedure is not specified, the battery can be replaced at the factory for all models presently in production. When replacing the battery, it is best to also consider replacing other parts, particularly the LCD, because these parts have a limited lifetime as well.

With an EEPROM, the EEPROM has a lifetime of approximately 100,000 writes and a data retention capability of approximately 10 years. The data retention capability poses no problems in actual use, but when considering the write life, particularly for Timers, applications with few power supply breaks are preferred. In other words, signal startup is preferable over power-supply startup.

Another difference is that because a lithium battery is a back-up method, function parameters can be set using front-panel keys, with no power supply necessary. This is not possible with EEPROM. In both methods, the function parameters can be set using DIP switches or a similar method, with no power supply necessary.