Southwest Airlines has started converting its 1,000-strong fleet of diesel baggage tractors and belt loaders to Thin Plate Pure Lead batteries from NexSys, a subsidiary of US battery firm EnerSys, in a move that has already seen other airlines express interest in doing the same.Steve Spaar, marketing director, Americas, at EnerSys said diesel-powered vehicles and those with flooded lead-acid batteries had been converted to the firm’s TPPL AGM batteries.

After an 18-month trial beginning at airports at Phoenix, Dallas and Los Angeles in 2014, the batteries were cleared and conversion of the entire fleet of more than 1,000 vehicles at various airports has begun.

“We are in the process of converting 60 diesel bag tractors at the Phoenix Sky Harbor International Airport and have installed NexSys batteries at Chicago Midway, Dallas/Fort Worth, Los Angeles, San Francisco and several other airports,” said Larry Laney, Southwest Airlines director of maintenance.

“The TPPL technology at the heart of these batteries is helping us facilitate our move away from diesel power, and we expect that it will help us save money in the process.”

“Tne NexSys TPPL life cycle is comparable to flooded lead acid battery life cycles,” said Spaar. “The NexSys battery can be charged at rates from 0.2C6 up to 0.7C6. The energy density of these batteries is higher in TPPL than flooded lead acid, so for a comparable flooded lead acid capacity, a TPPL battery will be lighter.”

As well as the weight disadvantage with flooded lead acid batteries, Southwest also encountered drawbacks with the requirement to regularly water them, something which if not carried out with precision will ultimately reduce performance and cycle life.

Although citing propriety reasons for not naming any other airlines, Spaar confirmed there had been interest.

“These batteries are suitable for any traction application where flooded lead acid or VRLA Gel or AGM batteries are being used now,” said Spaar.

“Because of their higher energy density, fast charging capability and the elimination of topping up, they are popular in floor cleaning machines, burden carriers, AGV/AGC and Class III vehicles.”