Although aircraft batteries arent high on our list of things to worry about, that isn’t the case for many owners, given the volume of reader mail we receive on this subject. Battery chargers figure into this concern, too, and following our report on this topic in January 2006, the subject has become, improbably controversial, spurred along by some new technological developments. By virtue of customer complaints about Gill sealed batteries, our previously recommended battery charger choice, the Battery Tender Plus by Deltran Corp., has been withdrawn from the aviation market and another company, VDC Electronics, has introduced an aviation-specific design based on charging profiles from the Concorde Battery Company. Our tests of this device show that its promising, with circuitry that reduces the peak charging voltage limit and lowers the float voltage for aviation AGM batteries. The charger also has a temperature sensor that keeps voltages optimized for storage environment, which will benefit batteries in hot hangars, in our view. In this report, we’ll examine this new technology and explore whether the aviation charger meets its claimed specifications and if its worth the money. (It does and it is.) For comparative purposes, were also looking at some off-the-shelf chargers.Surprisingly, many charging profiles are recommended by battery manufacturers and these profiles arent just limited to battery chemistry/construction types such as flooded and sealed cells. They also apply within the same genres and from brand to brand. To improve performance, higher end chargers have user settable profiles, something thats especially important for AGM-absorbed glass mat-batteries that are becoming popular for aircraft use. Temperature sensors have been around a long time, but have previously been restricted to high-end chargers used for multiple deep-cycle battery setups. Some chargers have a temperature sensor capability built into the charger itself, but this is a poor second to a ring terminal actually attached to the battery, such as the VDC aviation model has. The VDC aviation charger models 12248-AA and 24041-AA sense the battery temperature and protect the battery from getting too hot, as we’ll as adjusting the charger for the ambient external battery temperature. The unit also protects itself from excessive heat or output. Note the -AA model designation and that model without this suffix have a generalized charging profile, which uses higher voltage. These models don’t have the temperature sensor, although its available as an option. In recent years, the cost of user-selectable charger controls has decreased dramatically. For years, the $200 and up marine/RV chargers had user-selectable functions, but lower cost units generally had either low output or single-stage charging. Aviation battery makers have their house brands, but these are obscenely expensive. As a result, demand for sub-$75 chargers with so-called smart charging or multi-stage charging profiles has grown. So has interest in anti-sulfating technology that reduces the batterys tendency to self-destruct with time and/or disuse or incomplete charging. These chargers were limited to low current output, serving primarily as trickle or maintenance chargers. And no single charger that we know of had it all-smart 
Battery Chargers: VDC Winds in a Walk
Although aircraft batteries arent high on our list of things to worry about, that isn't the case for many owners, given the volume of reader mail we receive on this subject. Battery chargers figure into this concern, too, and following our report on this topic in January 2006, the subject has become, improbably controversial, spurred along by some new technological developments. By virtue of customer complaints about Gill sealed batteries, our previously recommended battery charger choice, the Battery Tender Plus by Deltran Corp., has been withdrawn from the aviation market and another company, VDC Electronics, has introduced an aviation-specific design based on charging profiles from the Concorde Battery Company. Our tests of this device show that its promising, with circuitry that reduces the peak charging voltage limit and lowers the float voltage for aviation AGM batteries.