Pilot's Guide to Avionics 2011-2012 - 81

PILOT’S GUIDE

Technology aside, your aircraft’s electrical system needs two things: a supply source capable of meeting the needs of the airplane when everything is turned on, and a battery and regulator matched to the system.

ent electrolyte mixture and two different plate materials: one is lead peroxide, the other pure spongy lead . Without taxing any memories of our chemistry classes, the simplest explanation for the “recombinant gas” aspect of the battery stems from the thin mats, the thin electrolyte layer between plates and mats, and the materials in the plates . Instead of the battery giving off hydrogen, the electrolyte gases off oxygen — and keeps the oxygen in close proximity to recombine with the sponge lead plate on the negative anode and maintain the same electrolyte chemistry . A valve system regulates pressures internally . The resulting plate designs RG technology made possible and the enclosed matting delivers a higher power density than the typical lead-acid battery . The batteries tend to last longer as well, offsetting the higher costs they might initially command . Over the lifespan of the battery, the costs tend to equalize . As replacements for NiCad

units, RG batteries cost less and generally provide a longer service life, adding further to their value equation . The RG batteries don’t suffer from the so-called “memory effect” that robs NiCads of their capacity over time . Special conditioners helped restore the capacity of NiCads, and the conditioning cycle needed to be run regularly to maintain peak battery performance . RG batteries need no such conditioning for capacity retention, although many manufacturers recommend using a battery conditioner to extend the life-span of both convention and RG lead-acid batteries . As a choice for an individual aircraft, you might find customers initially cautious about spending more on a battery that seems to have lower numbers — but produces equally good cranking power for engine start — and will last longer over time . If customers understand the longer-life/lower-maintenance equation, a higher price should dissolve in the face of a higher value equation .

Other Battery Needs If you’ve taken the smart step to install a new-generation 406 MHz ELT in your aircraft, you likely have one of these already working away for you . If you have any of the Aspen Avionics Evolution series of glasspanel hardware, or you’ve recently opted for a new backup battery for your panel, like the new units from Mid-Continent Instruments, you’ve got a lithium-ion battery at work for you . Li-ion batteries deliver a highpower density — lots of wattage per liter of volume — and generally perform without worries like developing a charge-level “memory” or a steadily declining output level . Li-Ion batteries deliver power at a steady level, until they fall off quickly at the end of their capacity . As with other batteries, they should meet the power needs of their installation and, if attached to the charging system — as some standby units might be — they should be compatible with the regulator’s output . Finally, most batteries only require periodic checking . q

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Pilot's Guide to Avionics 2011-2012

Table of Contents for the Digital Edition of Pilot's Guide to Avionics 2011-2012