Lithium-ion Batteries
In addition to the more established lead-acid and nickel-cadmium batteries, lithium-ion power solutions have become increasingly popular in recent times. Battery manufacturer True Blue Power has been installing lithium-ion batteries in rotorcraft since 2010, beginning with the True Blue Power TS835, a 4.5 amp-hour emergency backup battery for avionics and instruments. The company has also added lithium-ion main ship batteries, primarily for engine start applications, to its repertoire of certified battery options for rotorcraft. Lithium-ion batteries are available both in the U.S. and Europe and for installation on several helicopter types, including the Leonardo AW169, the Bell 505, the Robinson R44 and R66, and the Airbus H145 and H135. In addition the Sikorsky S-76D and S-92 and the Airbus AS350 currently have pending supplemental type certificates for the installation of lithium-ion batteries.
According to Rick Slater, a director at True Blue Power, lithium-ion batteries provide significant benefits compared with lead-acid and nickel-cadmium batteries. “Lithium-ion batteries are roughly half the weight of lead-acid and nickel-cadmium chemistries. They deliver a significant increase in power for high-power applications like engine or APU start and provide quicker and cooler engine starts on turbine aircraft. They offer good energy characteristics
for applications requiring longer availability of battery power and provide a very quick recharging profile compared to lead-acid and nickel-cadmium equivalents,” Slater says. “Lithium-ion batteries are virtually maintenance free; for True Blue Power batteries only a capacity check every two years is suggested. In addition, they have no memory effect like nickel-cadmium and no reblocking or desulfating like lead-acid. A lithium-ion battery has a much longer product life, which creates overall a significantly reduced cost of ownership that includes maintenance, replacement, aircraft down time and dispatch, reliability, and availability.”
Charging of lithium-ion batteries is accomplished through use of a standard ramp charging unit. “Lithium-ion batteries can be charged near lead-acid or ni-cad batteries and do not require special conditions or equipment. Lithium-ion batteries should not be discharged to zero as the battery could be damaged. Top charging to near capacity periodically is recommended if they are going to stay on a shelf for an extended period,” Slater says.
Like other types of batteries on the market today, not all lithium-ion batteries have the same kind of technology and safety features.
“The key factor in lithium-ion safety is a combination of cell chemistry, product architecture – relative to safety design – and certification testing. Some lithium chemistries are much more volatile than iron phosphate, particularly those with oxygen as a key element within their basic chemistry. Lithium iron phosphate is more manageable as it relates to heat generation. No oxygen content is present to exacerbate any potential situation involving fire,” Slater says. “Product architecture also affects safety. Having a large number of smaller lithium-ion cells versus a small number of large cells makes managing an exception condition, like a thermal runaway as a result of a single cell short circuit, much more manageable.”
Testing to FAA-specified requirements and receiving certification is the final step to ensure the battery can deliver what it promises, i.e. the ability to withstand complete thermal runaway with no damaging or permanent effects on the surrounding parts or components of the aircraft. “The FAA’s thorough testing and stringent specifications for rechargeable lithium-ion products provide a level of assurance to the pilot and passengers. True Blue Power is the only lithium-ion battery manufacturer to successfully achieve a technical standard order (TSO), type certificate (TC) and supplemental type certificate (STC), further validating the industry’s confidence in this technology and our advanced battery system designs,” Slater concludes.
True Blue Power TB17 lithium-ion battery installation in the Bell 505 Jet Ranger X
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