Nickel-Cadmium vs. Sealed Lead-Acid
Facts and opinions to ponder
Recombinant gas lead-acid batteries have made considerable headway into the aviation marketplace in the last several years. It used to be that if you had a particular aircraft, the size of the aircraft and the battery capacity requirements pretty much dictated which type of replacement battery you needed. Typically, the larger turbine-powered aircraft required high capacity nickel-cadmium batteries.
Today, technological developments in the lead-acid battery arena have resulted in larger "sealed," "maintenance-free," or "recombinant gas (RG)" batteries that are giving Ni-Cads a run for their money.
As expected, the manufacturers of the respective batteries have taken strong stands on the advantages, safety, cost, and performance of their respective products. Each claims that the cost over the long run is less than the other. Ni-Cad manufacturers claim that their batteries have a longer service life, longer shelf life, and are more easily maintained. The sealed lead-acid manufacturers say their products don't have to be maintained, are a fraction of the cost of Ni-Cads, and their performance is at par or better than the Ni-Cads.
Each has valid research to point to, and each uses solid logic to explain their opinions on the subject. Unfortunately, the water is muddied by the fact that different manufacturers use different specifications and testing parameters to prove their product's performance.
As a result, the end user is faced with taking the manufacturers' claims at face value or actually trying both. The following is intended to give you a leg up on the issues surrounding both types of batteries. It is presented in two parts: In Part 1, John McCoy, from Saft Aviation Batteries, one of the leading Ni-Cad battery manufacturers, reviews facts and opinion about both battery types. In Part 2, AMT interviews Skip Koss of Concorde Battery, one of the leading manufacturers of RG lead-acid batteries. Both articles represent the opinions of the respective parties and in no way represents AMT's viewpoint on the subject.Sealed lead-acid batteries
What you need to know about Nickel Cadmium and Valve regulated Lead-Acid batteries
By John McCoy Sales Manager, Aviation, for Saft Aviation Batteries
This discussion outlines the differences between nickel-cadmium aircraft batteries (NCAB) and valve regulated lead-acid batteries (VRLAB).
Construction — Valve Regulated Lead-Acid Batteries
In all electrochemical couples, there is a negative (anode) and positive (cathode) element. In VRLABs, these elements consist of pure lead (negative) and lead dioxide (positive). The positive and negative electrodes are prevented from coming into physical contact by a separator mechanism to prevent short circuits. In this case, the separator is the microporous glass mat filled with a solution of sulfuric acid and water.
Aviation VRLABs do not employ "gelled" electrolyte. Gelled electrolyte combines silica with sulfuric acid and water to limit the fluidity of the electrolyte. VRLABs typically "trap" the electrolyte in a microporous glass mat. The electrolyte in a VRLAB is the same as found in a flooded lead-acid battery, only there is less of it.
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