We have tested Concorde and Gill aircraft batteries on multiple occasions looking for the longest battery life and best value. In our view, and in our opinions expressed in our reader polls, Concordes products are a better bet. Our gold standard has been the FAA capacity test as the core of that test methodology since it takes each batterys amp-hour rating into consideration during the test, so we are testing apples-to-apples, so to speak. Per FAR 23.1353(h), we look for 80-percent capacity at the one-hour discharge rate. This simulates the stress of an alternator-out situation where battery power alone keeps the essential electronics bus running for a minimum of 30 minutes. There is no established standard for the number of cycles a battery must undergo, and we were only checking to see if the battery passed or failed each test. Obviously, doing this over and over takes a toll and ultimately as the cycles continued, some of the batteries started to fail the capacity test by reaching the cutoff voltage before they were supposed to-in other words, the capacity dropped below the 80-percent level-at which point we stopped testing that battery.
In each of the separate tests conducted a few years apart using three different type testers, we consistently found that Concorde and Gill flooded cells were close in their rated performance. However, Concordes generally have higher rated and actual amp-hour capacity out of the box than Gill. The Concorde flooded batteries also lasted several cycles longer than the Gills before they dropped below their official capacity rating. Two reader surveys returned similar opinions.
The Concorde sealed batteries performed better than their ratings, whereas, Gill sealed batteries just made their lower rating. Ultimately, the Concordes showed better performance throughout the test. So, in this limited quantity of batteries we tested on three separate occasions, it appeared the Concordes have greater cycle endurance before failing the capacity test, as we’ll as greater average amp-hour capacity ratings than their Gill counterpart. The Gills met their lower amp hour specs, but most did not last as many cycles in repetitive capacity testing.
In a final abuse test, we gave the sealed batteries a charge and let them sit for six months. We kept this six-month interval up until the batteries failed a capacity test. The Concorde AGMs finally failed the capacity test at 30 months (but we still use them around the shop). The Gills died at 12 and 18 months and could not be charged.
One area in which we were criticized in testing is that only three to four examples of each brand (12- and 24-volt and both flooded and sealed) were tested on each test. We freely admit this is not a large sample. But the results were repeated three times with three sets of different batteries for a total of over 20 batteries over the 10 years. The Concordes consistently won the match, so we feel confident in our opinion that they are the better value.
User OpinionsOur latest survey of user opinions turned up results consistent with our 2007 one.