The Battery That Won't Quit

Judge a Saft SPH Nickel-Cadmium (Ni-Cd) battery by its performance, not its age. This is the lesson engineers at a major telecommunications company in Houston, Texas, learned recently.

The battery system, installed in 1977, was used to black start emergency gas turbines at one of the company’s central facilities in Houston. This particular battery configuration was used to jump-start the backup generator in the event of an electrical outage. At the facility, these generators provide power for all electrical systems, ensuring operations continue uninterrupted. Although the Ni-Cd battery had been operating without failure, a new maintenance engineer insisted it be removed because of its age and replaced it with three automotive lead acid batteries in 2004.

The normal lifetime of a Ni-Cd battery in a backup power application is typically 15 to 20 years; however, the battery installed was performing perfectly until it was removed by the new maintenance engineer. Lead acid batteries seemed a logical short-term replacement for the engineer’s short tenure at the telecommunications company. This customer was thinking only in terms of age, not the record of performance.

Unfortunately, the long-term cost of constantly replacing lead acid batteries every three years will add up to much more than simply replacing the old batteries with new Ni-Cd batteries. Measuring the reliability of our battery by its age alone cost the company thousands of dollars.

It’s a common story for a Saft battery to exceed its normal life expectancy by more than 35% and many success stories go unaccounted for. This particular story came to light when the customer returned it to the factory for recycling. Saft includes the cost of recycling in the price of every new Ni-Cd cell. Saft submitted the battery configuration for independent verification and confirmed the entire package – five crates of five Ni-Cd cells (32VDC nominal total system voltage) – was still operating efficiently. The overall battery capacity was still performing at over 88%, with the lowest performing cell at 83% of its capacity.

A Ni-Cd battery ages linearly as opposed to a lead acid battery, which should be replaced at a certain age. Our batteries have a very predictable life cycle that consistently goes beyond the industry standard. In fact, there are literally thousands of our batteries in similar applications that have been in service for 30 years.

The returned batteries were still performing so well that Saft put them back into service. They are currently in use as a backup power source to provide emergency start-ups for generators in a Saft facility.

“Achieving longer than advertised performance from a Saft SPH Ni-Cd battery in any application isn’t unusual,” says Nick Finney, sales manager for the Saft Stationary Battery Group. “After the power outage in the Northeast, we received a number of positive reports from our customers. One telecom engineer reported that our eight-hour batteries lasted longer than 15 hours.”

Ni-Cd batteries were installed in many backup and emergency power applications during the power outage in the Northeast. Saft batteries successfully powered emergency lighting systems, switchgear and generators during the blackout.

The extended life of the SPH Ni-Cd technology can be attributed to a number of chemistry traits: (1) It is less sensitive to voltage surges, heat, direct lightning strikes and indirect electromagnetic influences; (2) 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); (3) It is tolerant to high ripple currents; and (4) Due to structural integrity, Ni-Cd plates are practically indestructible, protecting against sudden battery failure.

Given the advantages of a Ni-Cd solution, I don’t understand why any telecom engineer would select another kind. Battery reliability in generating starting applications has to be your number one priority when you’re thinking about chemistries. Our batteries don’t fail. Plus, their life cycle value is phenomenal compared to conventional lead acids that must be replaced every three years. I think the test results for the 28-year old battery from Houston say it all. After nearly three decades, it still had plenty of juice.