External battery for electrical testing

We have a 150G and a 182H, obviously both are older and occasionally we need to sit on the tarmac and play with electrical things inside for troubleshooting, calibrating, etc. We're concerned about running down the battery while doing so, and sometimes we'd rather not having the engine running - summertime inadequate cooling, wintertime too cold for short runs, etc. So I was just thinking whether we could power the bus through the cigar lighter, with the battery/master switch off to isolate the aircraft battery. I have an automotive jump battery that has a cigar to cigar plug, and I'm about to look through the schematic for the 150 - as that's the one I'm about to work on today. Wondering if anyone has done this before, or if there's something I might miss in the schematic. I need to adjust the 150's skyBeacon, so I'll be sitting on the ground with the transponder and nav lights on for awhile. Thanks

Comments

  • Scott ShererScott Sherer COO Forum Moderator
    edited December 2020

    You're going to be passing 12 volts at high current loads and you're on the right track but don't do it through your cigarette lighter. That's only made for a few amps and you're risking setting your panel on fire, lol. Rather, use jumper cables on your battery or your external power plug from an external power source. For example, another 12 volt battery or a battery eliminator like https://www.aircraftspruce.com/catalog/elpages/portPowerCharger.php

    Scott Sherer
    Wright Brothers Master Pilot, FAA Commercial Pilot
    Aviation Director, Cessna Owners Organization Forum Moderator and Cessna Owners Author.

    Need help? Let me know!

  • Okay. I opted to jump straight to the battery. Putting that battery box cover back on inside the 150 through the oil fill access is a real bear..

  • Scott ShererScott Sherer COO Forum Moderator

    Ha! Merry Christmas! Maybe Santa can find a way to do it, lol. :)

    Scott Sherer
    Wright Brothers Master Pilot, FAA Commercial Pilot
    Aviation Director, Cessna Owners Organization Forum Moderator and Cessna Owners Author.

    Need help? Let me know!

  • Here is thought since you do not have an external power port. Use an Anderson Powerpole SB50 connector wired to the battery with appropriately sized wire and fuse. The connector can be located in an accessible place and available anytime you might need it either for a maintenance charger or to power the ship for maintenance.

    I recommend not using wire smaller than 12 AWG, but you can go as large as 6 AWG. The main issue is voltage drop for the length of wire.

    This SB50 is the same connector used with the charger/battery eliminator Scott recommended above to attach the Cessna 3 prong plug (or Piper plug).

    I believe this is an A&P/AI minor alteration sign-off.

  • Appreciate the replies. We eventually ended up replacing the 4 year old battery. This plane had sat a lot for a bit, but then the club has been on a successful recruiting drive, and we were pushing 35-40 hours a month training through the winter. What we're thinking of doing now is getting a pullable circuit breaker to replace the fuses on the electric gyros, so if we need to run battery for any reason other than actual flying, we can reduce those loads we don't need.

  • I bought two inexpensive (<$50) computer power supplies for running airplanes in the hangar, one 13.5 volt and one 28. The power supplies have adjustment pots that let me set the voltage I want for the bus, and the output power is clean and stable.
    On our R182 I have set the external power supply to 28.3 volts. The power supplies produce up to 30 amps (12 volt) or 13.5 amps (28 volt), which is plenty for running all the radio stack as long as we want. On the 182 we have an avionics cooling fan that supplies radios with cooling air. On an airplane that gets cooling air from a ram air source you might want to limit how long you run it on the ground.

  • Hessaero,
    Be careful with the voltage you set these to. You only want to take the load off the battery and not try to charge the battery with these supplies. Otherwise you will ruin your battery.

    Aircraft batteries are not even close to car/truck batteries and are very sensitive. Even battery chemistry is different between manufacturers like Gill and Concorde and require a different charging rate. That is the reason the Aviation Battery Minder has different models for the Gill and Concorde.

    Car/truck chargers typically use a constant voltage system, but aircraft batteries prefer a constant current charge which decreases as the battery becomes fully charged by using smart technology.

    I suggest using 13.2 to 13.6 for your 12V system and 27.0 to 27.5 for your 28V system. Your setting of 28.3 Volts is a little much. What you can do is measure the voltage on your batteries before putting on the power supply. Adjust the voltage on your supply to 0.3 to 0.6 volts above the battery voltage. You only need to do this occasionally as the battery ages and not every time.

    BTW. Nice find. Just be careful.

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