Plane & Pilot
Tuesday, September 6, 2011

Caring For Your Aircraft


Part V: Understanding your aircraft’s battery is simple, useful and important


The biggest changes in battery technology have been in materials. Janak Rajpara, Director of Engineering for Teledyne/Gill (makers of Gill aircraft batteries) says, “The alloy composition between 1940 and now has significantly improved.” Rajpara says the aviation community is very price sensitive, and lead-acid batteries still provide the best price for performance. “Also, lead-acid batteries are 95% recyclable,” adds Rajpara, “which is important in our environmentally conscious world.”

Help Your Batteries Last Longer
Armed with knowledge, there are things pilots can do to help their batteries last longer. “I’ve seen customers bring in batteries that have been flying for over 10 years,” says Rajpara. He explains that the battery’s biggest enemy is high temperature and excessive discharge. “Pilots shouldn’t let a battery stay in a state of excessive discharge for too long. The key thing is to keep a battery charged and never to let it discharge severely.” Rajpara also suggests keeping your battery clean, and adding distilled water to nonsealed batteries. “You use distilled water because it has no dissolved solids to create competing chemical reactions.”

Skip Koss, Vice President of Marketing for Concorde Battery talked to us about the negative effects of “parasitic drain” on battery life. Parasitic drain refers to an electrical load that takes power from the battery even when the master switch or battery switch is off. Examples of components that cause parasitic drain are clocks, relays, lights and power-monitoring circuits, among others. These components will cause a slow drain of the aircraft’s battery in weeks or days—when the aircraft isn’t operated often. “Ultimately, a parasitic drain will cause the battery plates to sulfate,” says Koss. “Sulfated plates make the battery harder to recharge and, over time, can lead to a battery that’s no longer airworthy or will fail prematurely.”

Koss explains that one danger is a battery that can still start the engine but doesn’t have enough energy reserve in the event of an emergency. That battery won’t cause a pilot to notice anything unusual. Koss recommends measuring the parasitic drain on your particular battery using a standard digital multimeter. Procedures for this are published for free by Concorde Battery at www.concordebattery.com/otherpdf/tb10.pdf.

High temperature is another enemy of aircraft batteries. Janak Rajpara says the “danger zone” is anything over 110-120 degrees F, common during the summer months in western states. “At that point, the battery starts discharging very quickly,” he says. Long idles while running a lot of electronic components will quickly deplete your battery in those conditions. “If you want your battery to last longer, you need to keep it cool,” he suggests.

During winter months, having your battery tested is a good idea. Cold weather slows down the chemical reaction necessary to produce electricity in your battery. Also, cold batteries resist being charged. The amount of cranking power available from a cold battery is half of that available in a warm battery, because less current is produced due to the slowed-down chemical reaction. Several consumer-use units are available to test, maintain and charge your aircraft battery, or you can have it done by an aircraft mechanic.

As far as the future of batteries, both Concorde and Teledyne tell us that new material formulations are being looked at, and both nickel-cadmium and Li-Ion technologies are being developed further. The high-power Li-Ion battery shows promise—delivering superior life, half the weight and recharge in a fraction of the time it now takes for lead-acid and nickel-cadmium batteries. Concorde says another advantage of Li-Ion is that the battery has no “memory,” and no scheduled cycling is required to prolong the battery’s life. In addition, the self discharge is less than half compared to nickel cadmium. Teledyne is working on chargers that are more efficient and can resurrect a battery that has been discharged for a long time.

Even in the battery world, the trick is balancing the benefits of the technology with the cost to aircraft operators. New technologies aren’t as inexpensive as what we have today, and it remains to be seen where batteries will go in aviation. So, think about your humble battery next time you look at that ammeter during your run-up. Consider the work it has to do and what you as a pilot can do to keep it—and your entire electrical system—happy and functioning.



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