Power Electronics

NiCd Battery Still Runs After 28 Years

Saft recently uncovered a 28-year-old HIP nickel cadmium (Nicd) battery still in service at a major telecommunications company in Texas. The normal lifetime of a Nicd battery, in a typically harsh environment back-up power application, is in the range of 15 to 20 years.

Occasionally, Saft batteries exceed their normal life expectancy by more than 35%. This particular story came to light when the owner returned the Nicd battery to the factory for recycling because a maintenance engineer decided it was overdue for inspection.

Saft submitted the battery configuration for independent verification and confirmed the entire package of five crates of five Nicd cells (32-Vdc nominal total system voltage) was still operating efficiently. The overall battery capacity was still performing at more than 88%, with the lowest performing cell at 83% of its capacity.

The returned batteries were still performing so well that the independent test firm put them back into service in its own facility. The batteries are currently in use as a back-up power source to provide emergency start-ups for generators.

“Our batteries have a very predictable life cycle that consistently goes beyond the industry standard,” said Roy Gates, director of sales for the Saft Stationary Battery Group. “In fact, there are literally thousands of our batteries in similar applications that have been in service for 30 years.”

The Saft battery system, installed in 1977 for the San Antonio-based telecommunications company, was used to start emergency diesel generators at the company’s central facility. This particular battery configuration was used to jump-start the back-up generator in the event of an electrical outage. At the facility, these generators provide power for all electrical systems, ensuring operations continue uninterrupted.

Today’s replacement for the HIP is Saft’s SPH product portfolio; SPH batteries are designed for applications demanding a relatively high current over short periods. The extended life of the SPH Nicd technology can be attributed to a number of chemistry traits. For example, it is less sensitive to voltage surges, heat, direct lightning strikes and indirect electromagnetic influences.

The battery has a large electrolyte reserve and is hard to overcharge (in case of excessive overcharging, water replenishment is required, but this will not affect battery life). It also is tolerant to high ripple currents. Due to structural integrity, Nicd plates are practically indestructible, protecting against sudden battery failure.

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