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#14393 - 11/07/10 09:09 AM External Power Source for Avionics
MCM3M Offline
New Member

Registered: 11/07/10
Posts: 1
Loc: Florida
I am looking for a portable external power source appropriate for extended use of the KLN 94 for training in the aircraft while parked on the ramp. In looking at the schematic in the POH it does not appear that the battery is isolated when the external power receptacle is used. Has anyone had experience using one of the 24v portable booster packs for this purpose? I am wondering how long the booster pack might last before running down the aircraft battery.

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#14394 - 11/07/10 09:14 AM Re: External Power Source for Avionics [Re: MCM3M]
Rusty Rudder Offline
Platinum Pilot

Registered: 02/26/10
Posts: 4989
Loc: NorthEast
No idea, however, I was going to create a batterie pack, wire 2 or 4 batteries in series/parallel to obtain the proper voltage(24vDC in my case) and use a boat, 24 volt charger connected to it while working with the power on in the aircraft...
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Take-off's are optional, landings are manditory



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#14396 - 11/07/10 09:33 AM Re: External Power Source for Avionics [Re: Rusty Rudder]
November X-ray Offline
Club Sponsor
Gold Pilot

Registered: 08/15/10
Posts: 1589
Loc: Brookshire, Texas, USA
It depends on the amp/hour rating of the batteries, a 35 amp/hour battery will provide 35 amps for an hour. Will the training you mention require you to have the master on with all systems running? You may want to consider isolating the KLN-94 or pull fuses/open the breakers so there is no load going to anything else not needed and merely use a battery charger to augment your battery. I would not expect your training to go for hours at a time, I have no idea, but I would think the current draw would be minimal if only that device was the only draw on the system.
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#14397 - 11/07/10 09:33 AM Re: External Power Source for Avionics [Re: Rusty Rudder]
steve71e Offline
Second in Command

Registered: 02/22/10
Posts: 172
Loc: Atlanta, Ga
Don't know about that portable power supply, but "Battery Minder" now has one (110 volt) that plugs into your ground power plug and will give you 25 amps for playing with your avionics. It is only portable to the extent of the length of your extension cord though. Pretty pricey too. Think it is several hundred bucks. On my 79 Skyhawk, when you plug in the ground power plug, the ground power relay turns on, supplying power to the battery side of the master solenoid and battery, but you still need to turn on the master switch to get power to the buss and in the plane. Pretty sure all single Cessnas are like that, even the new ones. Cessna twins will power up as soon as you put power on the ground power plug like all Pipers. Your idea of a couple batteries, and 24 volt charger and ground power plug sounds like a good economical one !!
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#14419 - 11/07/10 07:44 PM Re: External Power Source for Avionics [Re: MCM3M]
Cessna Dude Offline
Diamond Pilot

Registered: 10/21/09
Posts: 6628
Loc: San Antonio, TX
Originally Posted By: MCM3M
I am looking for a portable external power source appropriate for extended use of the KLN 94 for training in the aircraft while parked on the ramp. In looking at the schematic in the POH it does not appear that the battery is isolated when the external power receptacle is used. Has anyone had experience using one of the 24v portable booster packs for this purpose? I am wondering how long the booster pack might last before running down the aircraft battery.
Welcome to the Cessna 172 Club MCM3M! Good, helpful folks here. Hope to see you around often!
_________________________
Due to certain economic uncertainty, the light at the end of the tunnel has been turned off until further notice.
Cessna 172, C172, C-172, Cessna Skyhawk fan.
www.cessna172club.com



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#14434 - 11/07/10 08:21 PM Re: External Power Source for Avionics [Re: Cessna Dude]
Lee T. Hargic Offline
Gold Pilot

Registered: 08/13/10
Posts: 1629
Loc: Louisville, KY
We had a desktop rack and a briefcase mount for the KLN90B/KLN88. They were useful in the classroom or briefing room. Good to learn the knob twisting and procedures on the ground. Don't know where to buy one but, they are out there.
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"A smart man learns from his mistakes. A wise man learns from the mistakes of others" -Anonymous

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