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  #21  
Old 01-08-2015, 08:37 AM
DennisRhodes DennisRhodes is offline
 
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Location: Taylorsville, Ga
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The OV protection is certanily a plus in those Alt like Plane Power and B&C which provide that protection. Appears that externally regulated alts may be easier to "add" that on. Looks like the site in post from Don might be an option but also needs a contactor, 5amp supply and some wire. would be nice to see that device incorporate the "contactor" and feed the B+ directly. That should be doable with today's electronics.
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  #22  
Old 01-08-2015, 12:24 PM
bigginsking bigginsking is offline
 
Join Date: Aug 2005
Posts: 36
Default B+ not just Field.

The OV failure mode in internally regulated auto alternators can be "self exciting" which, despite what you think, means that disconnecting the field isn't enough, you have to disconnect the current feed from the alternator(B+) also. So if you're using an internally regulated auto alternator(al la Vans standard) the OVP protection should include running the B+ through a contactor, the contactor should be powered by the field lead.

When the OV event happens, the crowbar pops the field breaker, the B+ contactor opens and the faulty alternator is completely isolated.

See page 2 here:
http://www.aeroelectric.com/DIY/DIY_Crowbar_OVP_F.pdf
Along with the warning not to use internally regulated alternators...

Electronics don't like heat... if you put the regulator behind the firewall you get to run 1000+ hrs with no alternator failures like me... I went through 2 automotive alternators in less than 100 hrs before I bucked up and got a B&C alternator...

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  #23  
Old 01-08-2015, 05:06 PM
aerhed aerhed is offline
 
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Location: Big Sandy, WY
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Why not just put the crowbar on the B+ CB or ANR?
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  #24  
Old 01-08-2015, 05:25 PM
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Walt Walt is offline
 
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Quote:
Originally Posted by aerhed View Post
Why not just put the crowbar on the B+ CB or ANR?
The crow bar would likely go up in flames before the main CB or ANR blew
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  #25  
Old 01-08-2015, 08:14 PM
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Sky Goddess Sky Goddess is offline
 
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Location: Spruce Creek Fly-In FL.---Stratham N.H.
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buy a 40amp DENSO alternator for 2000hrs trouble free operation----John
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  #26  
Old 01-09-2015, 09:10 AM
DennisRhodes DennisRhodes is offline
 
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Quote:
Originally Posted by Sky Goddess View Post
buy a 40amp DENSO alternator for 2000hrs trouble free operation----John
Actually that is what i ve been running since 2008. Good performance with No problem.
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  #27  
Old 01-09-2015, 09:50 AM
SHIPCHIEF SHIPCHIEF is offline
 
Join Date: Mar 2008
Location: Seattle
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The bulged Odyssey battery failed over time. It controlled the alternator's over voltage condition until it was over charged to the point it built up excess pressure and heat.
All the while, it was holding the system voltage down. I don't know how high the voltage initially went, but probably not enough to ruin modern dual voltage avionics.
Install a properly sized circuit breaker that can be manually opened on the alternator output wire. It would trip if the alternator 'went wild'. also, adding an over voltage alarm would inform the operator to manually open the circuit breaker.
Additionally, if you needed a bit more electricity to make it to the closest runway, the operator might briefly close the breaker to jolt some juice into the battery, then re-open the breaker?
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  #28  
Old 01-09-2015, 07:07 PM
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mv031161 mv031161 is offline
 
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Location: Tybee Island, GA
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Default Battery fAiled

The reason that battery looks that way: Ironically the battery sarted failing as we were approaching a paper pulp plant and a water plant which smells as bad as sulfuric acid! The sulfuric smell from the battery got worse and worse and we both thought it was the air outside! The EFIS never gave the PIC a warning and if it did, it got intepreted as something else. the engine parameter page was in minimized mode and the OV was not noted. See the trend here?

im glad we were close by our home airport. I was riding in the back close to the battery installation and my chest was on fire for a couple of days after! If that battery had caught on fire im sure there was nothing I could have done to extinguish it!

Few operational changes are in place now.
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