A commercial pilot for Delta Airlines who owns a single-engine, four-seat Diamond Aircraft DA40 airplane, was looking for a better way to power his avionics system. The all-glass cockpit in his airplane is a Garmin G1000, and is a 24-volt DC system. In order to power up the airplane's avionics, either the battery must be turned on (with the engine off), or the airplane's engine must be started and running. This either drains the airplane's battery, or burns and wastes high-cost aviation gas, and creates heat, loud noise and exhaust fumes. On the front right side of the airplane, there is an electrical DC power port that can be used to power the airplane's electrical systems via an external source of power, jump-start the airplane’s engine in case of battery failure via a spare 24-volt battery, or to charge the airplane battery using AC power and a transformer. The pilot flies his airplane frequently to several remote locations where there is no AC power.

The pilot approached Powerenz and asked if we could design a custom portable power system that would allow him to power up the airplane's 24-volt avionics system with the airplane engine off. He needed a unit that would:

a. utilize solar energy for fuel instead of liquid fuel or the plane’s battery,
b. be stored and carried in one waterproof, protective case, and by one person, c. be recharged by AC power when available, and
d. provide durable, long-term independence from the power grid.

A portable solar panel-battery system was designed and assembled that included the following components:

a. one high-quality, safe, 25.6-volt, lightweight, rechargeable lithium iron phosphate (LFP) battery assembly,
b. one 60-watt, high-efficiency, lightweight, foldable solar panel,
c. one 10.5-amp MPPT solar charge controller that establishes a safe and efficient electronic relationship between the solar panel and the battery,
d. proper fusing and wiring, and
e. one connecting adapter cable that mates with the aircraft DC power port.

The 25.6-volt battery provides a nominal 24 volts at the airplane DC port and is completely protected against electrical failure via a built-in protective circuitry module (PCM).

One or more solar panels could be draped over, and secured to, the surface of the airplane's right wing using Velcro straps, and left in place while parked until the next flight. Solar panels could also be positioned on the ground, the left wing, or elsewhere. Solar panels produce the most power when they face the sun perpendicularly, so location and tilt are important. To solar charge the battery, the power output connector from the solar panel(s) is linked to the solar power input connector of the solar charge controller-battery power unit, accessible inside the carrying case or bag. One LED light on the solar charge controller indicates when the battery is charging and fully charged. To recharge the battery from completely empty to full requires 5-6 hours of good sunlight when using one 60-watt solar panel, faster if a 2nd solar panel is added to the system, and longer if the conditions of sunlight are less than optimal. Since weight and safety are critical when flying, we chose to use a much lighter weight battery chemistry (LFP) rather than the much heavier lead acid version, and that decreased the weight of the system significantly. For safety, the battery is protected against short circuit current, other conditions of over-current, over-voltage, and under-voltage by a built-in PCM.

The portable solar power system can power up the airplane's avionics silently, without exhaust fumes, and without wasting aircraft fuel. The unit can be used for 3-4 hours before the batteries require recharging, longer if a larger battery is used. Two hours of power is more than enough time to flight plan, check weather, etc. During the preflight check, the airplane's engine does not have to be running, nor does the airplane's battery have to be used. When not in use, the portable system can be stored inside the airplane until it is needed again.

At Powerenz, a variety of portable solar power systems can be designed and assembled according to the needs of the pilot and his/her airplane. The personal needs of the pilot, and the electrical specs of the airplane are considered when we design a portable solar power system.

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