VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics


Go Back   VAF Forums > Avionics / Interiors / Fiberglass > Electrical Systems
Register FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
  #1  
Old 07-02-2019, 05:46 PM
blaplante blaplante is offline
 
Join Date: Jan 2010
Location: Southern California
Posts: 102
Question Ground Power socket connect using battery isolator?

I have the Piper style 2 connection socket for ground power. Not wanting the socket to be battery hot all of the time I have a contactor and switch to engage the socket. But thinking about this I wonder why this couldn't be simplified by using a Schottky battery isolator (high power rectifier) that would only allow current from the ground power *to* the ship? these are available in 200A and more ratings and drop about 1/2 of a volt.

Something like this https://www.mouser.com/ProductDetail...SABEgJ0GPD_BwE

although that one is a dual unit, but you get the idea.

Thoughts?
__________________
RV6A in phase 2 as of April 2016
Donation made Sept 2019
Reply With Quote
  #2  
Old 07-02-2019, 09:31 PM
Mich48041 Mich48041 is offline
 
Join Date: Apr 2008
Location: Riley TWP MI
Posts: 2,941
Default

Looking at the data sheet, the forward voltage drop will be more like 1 volt. I think that with a diode in the circuit, engine cranking will be degraded quite a bit. How about Bob Nuckolls' Z-31 ground power circuit? The socket is not hot unless the switch is turned on. Expensive avionics are protected against both reverse voltage and high voltage.
__________________
Joe Gores
RV-12 Flying
Reply With Quote
  #3  
Old 07-02-2019, 09:51 PM
vlittle's Avatar
vlittle vlittle is offline
 
Join Date: Jan 2005
Location: Victoria, Canada
Posts: 2,120
Default

Should work fine, if you parallel the diodes. The 200 Amp rating for each diode is for 50% duty cycle, so both are needed.

Bear in mind that there can be a leakage current, up to 160 mA if you short the plug or leave a load on it. This may not be a concern since you will be charging, jump starting or using it to power avionics loads.

This a lot lighter, less complex and more reliable than a contacter/diode based system, but it will be intolerant of overloads.

Good luck.
__________________
===========
V e r n. ====
=======
RV-9A complete
Harmon Rocket complete
S-21 under construction
Reply With Quote
  #4  
Old 07-03-2019, 08:26 AM
Carl Froehlich's Avatar
Carl Froehlich Carl Froehlich is offline
 
Join Date: Dec 2007
Location: Dogwood Airpark (VA42)
Posts: 2,191
Default

Recommend you consider not using one of these 1960 clunky ground power plugs at all.

Your airplane is not a car and should not be treated as such. If you need to jump start your airplane, you have better options than this. I offer:
- A dead battery(s) is a scream out to you that it has been neglected or abused. While a jump start might get the engine running, you would have no idea how much your battery capacity has been degraded.
- If you abuse your battery (like leaving a master on) consider that battery dead and replace it. While you might be able to breathe some life into it the damage is done. These days new Odyssey batteries are available in stores across the nation.
- If you simply drained the battery while playing with the panel, then charge it back to full capacity before launching into the ether. Here a easy jumper to a nice light 30 amp power supply (not a battery charger) will keep the battery(s) topped off while you spend hours hangar flying. Such power supplies are around $90: https://www.dxengineering.com/parts/...CABEgLR7fD_BwE

Do not run your panel on a battery charger.

Carl
Reply With Quote
  #5  
Old 07-03-2019, 09:40 AM
blaplante blaplante is offline
 
Join Date: Jan 2010
Location: Southern California
Posts: 102
Default reply

Yes, I have a proper modern charger for the PC680 chemistry, and yes I don't use a battery charger to run my avionics.

Regarding the voltage drop, the curves show 1 volt only at around 1000A... at 100A the drop is 0.6 volts.

I had missed the largish reverse leakage current spec - good catch. But I agree for the purpose it is not much of an issue.

-Bryan (BSEE 1977)
__________________
RV6A in phase 2 as of April 2016
Donation made Sept 2019
Reply With Quote
  #6  
Old 07-03-2019, 09:57 AM
vlittle's Avatar
vlittle vlittle is offline
 
Join Date: Jan 2005
Location: Victoria, Canada
Posts: 2,120
Default

Quote:
Originally Posted by Carl Froehlich View Post
Recommend you consider not using one of these 1960 clunky ground power plugs at all.

Your airplane is not a car and should not be treated as such. If you need to jump start your airplane, you have better options than this. I offer:
- A dead battery(s) is a scream out to you that it has been neglected or abused. While a jump start might get the engine running, you would have no idea how much your battery capacity has been degraded.
- If you abuse your battery (like leaving a master on) consider that battery dead and replace it. While you might be able to breathe some life into it the damage is done. These days new Odyssey batteries are available in stores across the nation.
- If you simply drained the battery while playing with the panel, then charge it back to full capacity before launching into the ether. Here a easy jumper to a nice light 30 amp power supply (not a battery charger) will keep the battery(s) topped off while you spend hours hangar flying. Such power supplies are around $90: https://www.dxengineering.com/parts/...CABEgLR7fD_BwE

Do not run your panel on a battery charger.

Carl
All of the above are good recommendations, and ones that I practice as written.
See schematics:

http://www.vx-aviation.com/sprocket/...s-2/MASTER.pdf

http://www.vx-aviation.com/sprocket/...ics-2/ELEC.pdf

But when you are stuck on the ground in Lower Upchuck it sure would be nice to jumpstart the aircraft to get to a real airport for servicing.

I had a battery failure and managed to charge it through my always hot 12V accessory plug (second link above). The mechanic who provided the charger stayed late to help me out... at no charge.

But for those who choose a GPU plug, the diode looks like it will work.
__________________
===========
V e r n. ====
=======
RV-9A complete
Harmon Rocket complete
S-21 under construction
Reply With Quote
  #7  
Old 07-03-2019, 10:48 AM
jeffkersey's Avatar
jeffkersey jeffkersey is offline
 
Join Date: Sep 2015
Location: Cottontown, TN
Posts: 240
Default Quick connect....

I put a quick connect jumper, similar to this ( https://www.northerntool.com/shop/to...9606_200609606 ) just inside the oil door. My battery is on the engine side of the firewall. I would not be able to get the cowl back on after the motor was started with out this setup. I hope I never have to use it but have it if I needed it in a pinch.
__________________
Jeff Kersey
RV7A Purchased Flying
Dues paid
Reply With Quote
  #8  
Old 07-03-2019, 12:32 PM
rv7charlie rv7charlie is offline
 
Join Date: May 2006
Location: Pocahontas MS
Posts: 3,871
Default

If you want to roll your own, those connectors are used as charge connectors on electric fork lifts, and I think I've seen them on electric golf carts, as well.

If the goal is primarily emergency 'jump start', planes with a firewall mounted battery can use a simple 'hot' post located where it's accessible through the cooling exit. Cap it with an insulating boot that can be removed or pushed out of the way for the jumper cable. Exhaust pipes or an engine mount bolt for ground.

FWIW, any of the options discussed do leave you vulnerable to potential overvoltage, if a careless line person hooks you up to the 24V (or jet) start cart. The contactor detailed in AEC has OV protection.
Reply With Quote
  #9  
Old 07-03-2019, 08:17 PM
blaplante blaplante is offline
 
Join Date: Jan 2010
Location: Southern California
Posts: 102
Default Hot Post?

Maybe I'm a nervous one, but a (always?) 'hot post' down the the lower cowl make me concerned. Why? Take an off airport landing... high probability of ripping the gear off, and now the hot post is banged into the firewall. Lots of sparks. And in that landing there's probably a ruptured tank...

Maybe because I saw I guy short out a car battery and had the battery literally blow up in his face that I'm nervous about shorts.

Seems like another place to use an isolator or relay so it isn't hot always.
__________________
RV6A in phase 2 as of April 2016
Donation made Sept 2019
Reply With Quote
  #10  
Old 07-03-2019, 09:14 PM
rv7charlie rv7charlie is offline
 
Join Date: May 2006
Location: Pocahontas MS
Posts: 3,871
Default

Good point. I've got a 'hot post' in my -4, but it's accessible through the oil door. I never intend to use it for jump starting; only for charging the battery. Obviously not as safe as nothing at all, but pretty close. The battery sits on the footwell shelf, so the wire is about a foot long, and above a top motor mount tube.

The only reason I mentioned making it accessible in at least a marginally safe area for jump starting.
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 01:30 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.