Guide to mains-powered continuous DC power supplies for aircraft maintenance. 25A to 600A units from Red Box, Powervamp, and ITW GSE for avionics work and extended ground power.
What Are Continuous Power Supplies?
A continuous power supply delivers stable, regulated DC voltage to an aircraft for extended periods — hours rather than the seconds that a battery start unit provides. These mains-powered units plug into a standard wall outlet (110V/230V AC) and output clean 14V or 28V DC at continuous ratings from 25A to 600A. They're the backbone of avionics shops, maintenance hangars, and any facility where aircraft systems need power without running the engine.
How They Work
Continuous power supplies use transformer-rectifier or switch-mode power conversion to transform AC mains power into regulated DC output. The key difference from battery start units is sustained output capacity: where a battery GPU delivers a brief burst of thousands of amps, a continuous supply delivers tens to hundreds of amps indefinitely. Output voltage regulation is critical — avionics systems require stable voltage within tight tolerances, and a supply that drifts or produces excessive ripple can cause intermittent faults or damage sensitive electronics.
Manufacturer Comparison
Choosing the Right Continuous Power Supplie
The primary use case for continuous power supplies is maintenance: avionics installation, software updates, system testing, and troubleshooting that requires the aircraft's electrical systems to be powered for hours. Running the engine solely to power the avionics bus is wasteful, noisy, and produces exhaust that maintenance crews shouldn't breathe in an enclosed hangar.
For light aircraft maintenance, a 25A to 50A continuous supply handles most tasks — Garmin G1000 updates, radio programming, transponder testing, and instrument checks rarely draw more than 20A in aggregate. Medium turboprops and light jets with more complex avionics (Pro Line 21, Garmin G5000) benefit from 100A to 200A continuous supplies that can power the full flight deck plus cabin systems simultaneously.
Heavy maintenance on large-cabin jets and commercial aircraft requires 400A+ continuous supplies or dedicated airport ground power infrastructure. At this level, the distinction between a continuous supply and a TRU blurs — the same equipment often serves both functions.
Output quality matters. A cheap power supply with high ripple voltage or poor regulation can cause avionics faults that disappear when the engine is running, leading to expensive troubleshooting chases. Look for supplies with less than 1% ripple at rated output and voltage regulation within ±0.5V.
For a step-by-step approach to selecting the right GPU for your aircraft, see our GPU Sizing Guide. For a comparison of lead-acid vs lithium technology, read Lead Acid vs Lithium GPUs.
Recommended For These Aircraft
Related Product Categories
Frequently Asked Questions
What's the difference between a continuous supply and a TRU?
Both convert AC to DC, but a TRU is designed for high peak current output (engine starting) while a continuous supply is optimized for sustained, clean output at lower current (maintenance power). Some units, like the ITW GSE 2400, do both.
Can I use a continuous supply to start an engine?
No. Continuous supplies are rated for sustained output at tens to hundreds of amps, not the thousands of amps required for engine starting. Use a battery start unit or TRU for engine starts, and a continuous supply for maintenance.
What size continuous supply do I need for avionics work?
For light piston aircraft (Cessna 172, Cirrus SR22): 25 to 50A. For turboprops (King Air, PC-12): 50 to 200A. For jets (Citation, Learjet): 100 to 400A. Size based on the maximum combined load of all systems you'll power simultaneously.