Sizing up standby batteries

Standby batteries and equipment are like the ugly sisters in the Cinderella story: Maybe unlovely but absolutely crucial to the plot.

Lead acid is easily the king of the hill in telecom standby battery terms, accounting for more than 90% of the estimated $1.4 billion global annual market.

The main thrust of valve regulated lead acid (VRLA) development seems to be to make the batteries cheaper and easier to replace. However, EnerSys (formerly Yuasa) recently announced that it had tripled the life span of one family of VRLA batteries, up from the industry standard average of three to five years to 15 years.

Using several internal design advances, EnerSys says it has reduced the rate and impact of positive plate corrosion on its REL-B family of VRLA batteries. According to the company, this has resulted in less grid distortion and better contact between the grid and active material.

A life expectancy of 20 years or more, at an ambient temperature of 20 C, is claimed for a newer telecom standby battery technology: nickel cadmium, or Ni/Cd (see figure). Ni/Cd is a fairly recent phenomenon in telecom and has been pioneered by France-headquartered SAFT.

SAFT claims that if aggregated life cycle costs — including preventive maintenance, replacement and downtime — are factored in, Ni/Cd starts to cost less than VRLA after three to six years of duty.

The company says that with Ni/Cd, the maintenance interval can be longer than the entire lifetime of a typical VRLA. It also notes that VRLA air conditioning is both power- and maintenance-greedy, and Ni/Cd will withstand much higher temperatures than VRLA.

Also coming down the standby battery turnpike is the development of nickel metal hydride, or Ni/MH, batteries. This Ni/MH is a mature technology for portable re-chargeable applications, but it is still being trialed for standby applications.

Ni/MH has two compelling advantages over Ni/Cd: Its compactness and the fact that it weighs about 10 times less. But it remains much more expensive than Ni/Cd.

Another future possibility is lithium, which is even more compact and lighter than Ni/Cd. The hope is that if the required lithium price and performance points can be achieved, lithium would be a natural for powering pole-mounted telecom equipment such as microbase stations.

“We will reveal some very promising laboratory test results at Intelec in October in Edinburgh, [Scotland],” said Antoine Brenier, SAFT marketing manager. “These results make me very confident that lithium is going to be an extremely interesting alternative to Ni/Cd.”