United Rotorcraft Solutions (URS) expects award of a FAA Supplemental Type Certificate (STC) for their Lead Acid Battery Maintainer by March 1, 2010.
The benefits of the URS battery maintainer are automatic switch-mode battery charger; input: 115VAC, output: 24VDC, 2Amp constant current, automatic cut-off and true float.
It can be left on without harming the battery.  It also provides de-sulfation of battery and increases battery life.  It has reverse polarity protection, short circuit protection and over voltage protection, soft start and stop: no in-rush of current protects the battery.   It is FCC Class B EMI interface compliant and is safe for FADEC.
The system has the provisions for shore power (110vac outlet in airframe) and has an enunciator light in the instrument panel that illuminates when shore power is connected.
The system weighs less than 5 pounds installed and the kit comes complete with all required hardware and wiring.
United Rotorcraft Solutions, FAA Repair Station UX9R241Y, provides aircraft completions and refurbishment services, systems integration, maintenance, component overhaul, customized interior installations and unsurpassed exterior finishing.  They also offer FAA approved NVG compatible lighting systems for many model helicopters.