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Dual Battery Contactor

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rv8iator

Joined: 11 Apr 2006
Posts: 144
Location: Newberg, OR

Posted: Mon Dec 07, 2009 10:05 am Post subject: Dual Battery Contactor

Just came across a new (to me) product from Cole Hersee.  This is a battery contatctor with a dual battery voltage sensor and control module added on.  From the literature this appears to be a simple solution to automatic isolation and control of a dual battery, single alternator electrical system.



Take a look at the lit. and comment.  Upon first blush this appears to supplant the dual contactor with a single contactor and a voltage sense and control circuit.



http://www.colehersee.com/pdf/hot_feed/D-617_SmartBatteryIso.pdf

Chris Stone

RV-8

Newberg, OR

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C. Stone (RV8iator)

skywagon

Joined: 11 Feb 2006
Posts: 184

Posted: Mon Dec 07, 2009 3:37 pm Post subject: Dual Battery Contactor

Chris,

Thanks for the tip and lead on a great solution for preserving alternators 

from high stress loads...

David

C185D

Grants Pass, OR



---

dgolden(at)golden-consult
Guest

Posted: Mon Dec 07, 2009 4:49 pm Post subject: Dual Battery Contactor

Chris Stone wrote:

 	  Quote: 	
		   Just came across a new (to me) product from Cole Hersee.  This is a battery

 contatctor with a dual battery voltage sensor and control module added on.

 From the literature this appears to be a simple solution to automatic

 isolation and control of a dual battery, single alternator electrical system.

 

 

 Take a look at the lit. and comment.  Upon first blush this appears to

 supplant the dual contactor with a single contactor and a voltage sense and

 control circuit.

 

 http://www.colehersee.com/pdf/hot_feed/D-617_SmartBatteryIso.pdf


	


<snip>



This looks very much like what Yandina (marine electronics) calls a combiner. I

have one on my 1976 GMC motor home. It is installed across the factory installed

isolator (diode). The difference that I see, is that the combiner we're using on

our motor homes works both directions (i.e. chassis -> house and house ->

chassis). What this means is that if we are on the road it charges the house

battery(s) and if we are docked with shore power (or the generator running), the

chassis battery will also be charged.



It works as advertised and I'm happy with it. I have the Cobiner 100 (good for a

100 amp alternator). It lists at $79.95 and on sale for $59.95 which is what I paid.



Regards,



Dennis

-- 

Dennis Golden

Golden Consulting Services, Inc.

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Dec 07, 2009 6:44 pm Post subject: Dual Battery Contactor

At 12:01 PM 12/7/2009, you wrote:



 	  Quote: 	
		  Just came across a new (to me) product from Cole Hersee.  This is a 

battery contatctor with a dual battery voltage sensor and control 

module added on.  From the literature this appears to be a simple 

solution to automatic isolation and control of a dual battery, 

single alternator electrical system.



Take a look at the lit. and comment.  Upon first blush this appears 

to supplant the dual contactor with a single contactor and a voltage 

sense and control circuit.


	


 	  Quote: 	
		  http://www.colehersee.com/pdf/hot_feed/D-617_SmartBatteryIso.pdf




	


    It appears to be a "smart" contactor that doesn't close

    until the upstream system voltage exceeds 13.2 volts.

    It appears also that you can force the contactor closed

    for cranking assist.



    I.e. just like a plain vanilla aux battery contactor with

    an aux battery management module built in. You'd still

    have a manually switched battery master contactor.



        Bob . . .

                    ////

                   (o o)

    ===========o00o=(_)=o00o=========

    < Go ahead, make my day . . .   >

    < show me where I'm wrong.      >

    =================================

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Dec 08, 2009 9:02 am Post subject: Dual Battery Contactor

At 05:34 PM 12/7/2009, you wrote:




Chris,

Thanks for the tip and lead on a great solution for preserving 

alternators from high stress loads...



    Not sure there is "benefit" to be realized for shielding

    an alternator from "high stress" loads.



    As converters of mechanical to electrical energy, these

    devices have specifications. They also tend to be designed

    for a particular marketplace task. The prudent designers,

    manufacturers and installers of such devices understand the

    capabilities and limits. That understanding is factored

    into satisfaction of design goals and establishment

    of maintenance programs.



    Subscribing to the notion of "stress mitigation" on

    an alternator by programming the manner in which loads

    are applied to the machine suggests that design goals,

    capabilities and limits are suspect or perhaps known

    to be poorly married.



    The aux battery management module for OBAM aircraft was

    first proposed in an article I wrote for Sport Aviation

    many moons ago. The intent of this device was to provide

    automatic management of an auxiliary battery included

    to power flight critical electro-whizzies. The ABMM

    prevented connection of the aux battery to the system

    unless bus voltage was high enough to avoid discharging

    the battery (i.e. alternator on line). Hence the 13.0

    volt switchpoint calibration  for closing the contactor.

    The corollary idea was that the ABMM opens the contactor

    automatically during alternator shut down or failure

    thus isolating the aux battery and preserving contained

    energy for a specific task.



    The product being discussed appears to perform in

    precisely the same manner where it's desirable

    to isolate a RV vehicle battery from recreational

    electro-whizzies battery unless the alternator

    is available to service BOTH batteries.



    This is a PARTICULAR case where the recreational

    battery is EXPECTED to be deeply discharged. Now,

    if the vehicle battery has not been abused while

    parked, then the bus is expected to rise above

    13.0 (or 13.2) volts seconds after the engine

    starts. This device would spare the alternator

    from "high stress" loads only if BOTH batteries are

    deeply discharged. But even then, I can't imagine

    that the bus will stay below 13.2 volts for very

    long even if the vehicle battery was drawn down

    completely and the engine was started with jumper cables.



    Finally, irrespective of number of batteries and

    no matter how you've abused the batteries, your

    alternator should be EXPECTED to happily deliver

    full rated output for an indefinite period of time.

    If not, there's something wrong with the selection

    of alternator or the manner in which it has been

    installed.



    Bob . . .

rv8iator

Joined: 11 Apr 2006
Posts: 144
Location: Newberg, OR

Posted: Tue Dec 08, 2009 10:22 am Post subject: Dual Battery Contactor

This brings to mind a question as to what happens to the alternator when the load placed on it exceeds it's output capacity?  Will the output voltage start to drop as capacity is exceeded?  If overload is continued are the diodes the weak link in the chain?  Will the diodes fail before overheating of the stator windings?  What is the common failure mode?



Chris Stone

RV-8



--

_________________
C. Stone (RV8iator)

longg(at)pjm.com
Guest

Posted: Tue Dec 08, 2009 12:43 pm Post subject: Dual Battery Contactor

Chris,



As Bob noted, the alternator will continue to output at its rated capacity as long as the regulator is demanding it. Each alternator should be able to run at its rated capacity for N hours before failing (some calculus test performed at the factory).



The bigger question is what are you doing in your cockpit while you are waiting for the alternator to explode and your bus architecture to melt down? Answer, you should be activating your fire gear. No, a diode won't immediately melt if you drop to 8 volts, but by then you should have your contingency plan in action. Should you experience 1 or more failures in any situation, you should start shedding load and if the alternator seems to be a problem, shut it down.



Two heads are better than one and one good battery and two alternators are better than 2-3 batteries any day.



Glenn

--

nuckolls.bob(at)aeroelect
Guest

Posted: Tue Dec 08, 2009 4:11 pm Post subject: Dual Battery Contactor

At 02:40 PM 12/8/2009, you wrote:

 	  Quote: 	
		  



Chris,



As Bob noted, the alternator will continue to output at its rated 

capacity as long as the regulator is demanding it. Each alternator 

should be able to run at its rated capacity for N hours before 

failing (some calculus test performed at the factory).


	


   In the aviation world we test alternators/generators/motors to rated

   loads and worst case temperatures to meet specifications. If the customer

   observes published limits, they have a high probability of seeing

   the laboratory experience repeated in the field.



 	  Quote: 	
		  The bigger question is what are you doing in your cockpit while you 

are waiting for the alternator to explode and your bus architecture 

to melt down? Answer, you should be activating your fire gear. No, a 

diode won't immediately melt if you drop to 8 volts, but by then you 

should have your contingency plan in action. Should you experience 1 

or more failures in any situation, you should start shedding load 

and if the alternator seems to be a problem, shut it down.



Two heads are better than one and one good battery and two 

alternators are better than 2-3 batteries any day.


	


   Exactly. I'll re-enforce that idea with the notion that

   except for unanticipated failure, NOTHING that goes on

   in your electrical system should be a surprise. I've written

   often about failure mode effects analysis wherein all

   normal and abnormal operating conditions are deduced,

   studied for deleterious effect to be mitigated by design.



   The ONLY way you're going to beat the (at)#$(at)# out of your

   alternator is to jump-start with a DEAD battery and

   then launch into the blue with all your electro-whizzies

   turned on. Until the battery's recharge demands begin to

   taper, the alternator will be running flat-out. The duration

   of this event is generally a few tens of minutes at the

   most. All other times, I would hope that the builder has

   PREDICTED what loads can be serviced under any/all

   conditions and is operating the airplane accordingly.



   Chapter 17 in the 'Connection speaks to this process

   in detail.  I've also suggested that the hierarchy of

   importance for surviving the flight experience stacks

   up like this:(a) airframe, (b) owner/builder/pilot

   (c) powerplant (d) all other things.



   The significance of the second item goes far beyond

   the knowledge and skills needed AFTER the wheels are

   up. There is a great deal that can be done in the

   craftsmanship, understanding and decisions made long

   before the airplane leaves the shop . . . like due

   diligence to the study of category (d).

   Bob . . .

[quote]Glenn

--

rv8iator

Joined: 11 Apr 2006
Posts: 144
Location: Newberg, OR

Posted: Wed Dec 09, 2009 6:20 am Post subject: Dual Battery Contactor

Great thread!  Thanks.



Chris

[quote]>

>Chris,

>

>As Bob noted, the alternator will continue to output at its rated 

>capacity as long as the regulator is demanding it. Each alternator 

>should be able to run at its rated capacity for N hours before 

>failing (some calculus test performed at the factory).



   In the aviation world we test alternators/generators/motors to rated

   loads and worst case temperatures to meet specifications. If the customer

   observes published limits, they have a high probability of seeing

   the laboratory experience repeated in the field.



>The bigger question is what are you doing in your cockpit while you 

>are waiting for the alternator to explode and your bus architecture 

>to melt down? Answer, you should be activating your fire gear. No, a 

>diode won't immediately melt if you drop to 8 volts, but by then you 

>should have your contingency plan in action. Should you experience 1 

>or more failures in any situation, you should start shedding load 

>and if the alternator seems to be a problem, shut it down.

>

>Two heads are better than one and one good battery and two 

>alternators are better than 2-3 batteries any day.



   Exactly. I'll re-enforce that idea with the notion that

   except for unanticipated failure, NOTHING that goes on

   in your electrical system should be a surprise. I've written

   often about failure mode effects analysis wherein all

   normal and abnormal operating conditions are deduced,

   studied for deleterious effect to be mitigated by design.



   The ONLY way you're going to beat the (at)#$(at)# out of your

   alternator is to jump-start with a DEAD battery and

   then launch into the blue with all your electro-whizzies

   turned on. Until the battery's recharge demands begin to

   taper, the alternator will be running flat-out. The duration

   of this event is generally a few tens of minutes at the

   most. All other times, I would hope that the builder has

   PREDICTED what loads can be serviced under any/all

   conditions and is operating the airplane accordingly.



   Chapter 17 in the 'Connection speaks to this process

   in detail.  I've also suggested that the hierarchy of

   importance for surviving the flight experience stacks

   up like this:(a) airframe, (b) owner/builder/pilot

   (c) powerplant (d) all other things.



   The significance of the second item goes far beyond

   the knowledge and skills needed AFTER the wheels are

   up. There is a great deal that can be done in the

   craftsmanship, understanding and decisions made long

   before the airplane leaves the shop . . . like due

   diligence to the study of category (d).

   Bob . . .

>Glenn

>--

_________________
C. Stone (RV8iator)

user9253

Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan

Posted: Wed Dec 09, 2009 9:00 am Post subject: Re: Dual Battery Contactor

 	  Quote: 	
		  "Two heads are better than one and one good battery and two alternators are better than 2-3 batteries any day."  And Bob Nuckolls replied, "Exactly. I'll re-enforce that idea . . . . ." 	


I am not disagreeing but have questions:



Suppose that it is impractical to install two alternators on an electrically dependent engine in a VFR airplane.  If a battery is properly maintained and periodically tested for capacity, is its risk of failure high enough to warrant  a backup battery?



What if a cell in the battery shorts out?  Will the alternator keep working?  If no, then will the battery still have enough voltage and contain enough energy to supply the ignition system until a landing can be made?  I assume yes, but do not know.



A small backup battery will provide peace of mind, knowing that there is an alternate current path in case of a failed terminal or connection in the main circuit.  But is the benefit worth the extra weight?



Joe

_________________
Joe Gores

Sam

Joined: 18 May 2008
Posts: 135

Posted: Wed Dec 09, 2009 9:24 am Post subject: Dual Battery Contactor

Joe, I have an electrically dependent VFR plane, and I concluded that yes, it is worth it= to have the second battery.  I like to fly long cross countrys and from time to time I am over very lonely territory.-



Did you do a full electrical analysis of your devices for takeoff, climb, cruise, descent, landing, etc?  That should point out what you need. I'm going to try attaching one for you, if it doesnt go I will e-mail it to you offline.  It's not perfect, but you get the idea.

 

I wound up using two batteries of the same size.  I figured in the long run that would simplify things for me.



Regards.



Sam Hoskins

www.samhoskins.blogspot.com

 



 	  Quote: 	
		  	




On Wed, Dec 9, 2009 at 11:00 AM, user9253 <fran4sew(at)banyanol.com (fran4sew(at)banyanol.com)> wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "user9253" <fran4sew(at)banyanol.com (fran4sew(at)banyanol.com)>

  

 

 > "Two heads are better than one and one good battery and two alternators are better than 2-3 batteries any day."  And Bob Nuckolls replied, "Exactly. I'll re-enforce that idea . . . . ."

 

 I am not disagreeing but have questions:

 

 Suppose that it is impractical to install two alternators on an electrically dependent engine in a VFR airplane.  If a battery is properly maintained and periodically tested for capacity, is its risk of failure high enough to warrant  a backup battery?

  

 What if a cell in the battery shorts out?  Will the alternator keep working?  If no, then will the battery still have enough voltage and contain enough energy to supply the ignition system until a landing can be made?  I assume yes, but do not know.

  

 A small backup battery will provide peace of mind, knowing that there is an alternate current path in case of a failed terminal or connection in the main circuit.  But is the benefit worth the extra weight?

 

 Joe

 

 --------

 Joe Gores

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=276838#276838

 

 

 

 

 

 

 

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Sam Hoskins
www.samhoskins.blogspot.com

longg(at)pjm.com
Guest

Posted: Wed Dec 09, 2009 9:48 am Post subject: Dual Battery Contactor

Joe,



Fair question. Certainly not every installation (especially air-motive

types) will lend themselves to dual alternators. The second best backup

would be a second battery. As far as the alternator is concerned, let's

say for example the airplane started under its own power and the battery

had an issue as you flew along. The alternator would still generate

charging energy because it is already excited, however the battery is no

longer benefiting as it will not absorb the charge.



You may have experienced this in your car. You start your car, drive to

work and upon leaving work your car doesn't start, yes? Same deal. This

is why the landfill is full of old batteries and Pep 

Boys is rich. 



I find this retarded, but did you ever see someone jump start an

airplane and then take off into the wild blue yonder with their

alternator charging a junk battery? Happens every day. I, like you am

electrically dependent and my pet peeve is to ensure I have a battery

that will hold a starting charge for at least two weeks and perform at

normal or below temperatures when requested. It should, on occasion pass

Bob's recommended battery stress test.



A respectable RG battery will not have a catastrophic failure but will

go bad over time. Is the benefit of the extra battery worth it? How many

hours have you flown on one battery with your teeth grinding? One may

never fail, but two will make you feel better. For me two alternators

and one well maintained battery offers ample security and redundancy.



If I had a Subaru or other electrically dependent alternative air-motive

engine without second alt , I'd have a second battery, period.



Get out and fly!



Glenn



--

longg(at)pjm.com
Guest

Posted: Wed Dec 09, 2009 9:51 am Post subject: Dual Battery Contactor

Sam,  

   

FYI, great job on the plane! I’ve always liked this design. Maybe next build.  

   

Glenn  

     

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Sam Hoskins

 Sent: Wednesday, December 09, 2009 12:22 PM

 To: aeroelectric-list

 Subject: Re: Re: Dual Battery Contactor  

  

   

Joe, I have an electrically dependent VFR plane, and I concluded that yes, it is worth it= to have the second battery.  I like to fly long cross countrys and from time to time I am over very lonely territory.-

 

 Did you do a full electrical analysis of your devices for takeoff, climb, cruise, descent, landing, etc?  That should point out what you need. I'm going to try attaching one for you, if it doesnt go I will e-mail it to you offline.  It's not perfect, but you get the idea.

 

 I wound up using two batteries of the same size.  I figured in the long run that would simplify things for me.

 

 Regards.

 

 Sam Hoskins

 www.samhoskins.blogspot.com

 

   

     

On Wed, Dec 9, 2009 at 11:00 AM, user9253 <fran4sew(at)banyanol.com (fran4sew(at)banyanol.com)> wrote:  

--> AeroElectric-List message posted by: "user9253" <fran4sew(at)banyanol.com (fran4sew(at)banyanol.com)>

 

 

 > "Two heads are better than one and one good battery and two alternators are better than 2-3 batteries any day."  And Bob Nuckolls replied, "Exactly. I'll re-enforce that idea . . . . ."

 

 I am not disagreeing but have questions:

 

 Suppose that it is impractical to install two alternators on an electrically dependent engine in a VFR airplane.  If a battery is properly maintained and periodically tested for capacity, is its risk of failure high enough to warrant  a backup battery?

 

 What if a cell in the battery shorts out?  Will the alternator keep working?  If no, then will the battery still have enough voltage and contain enough energy to supply the ignition system until a landing can be made?  I assume yes, but do not know.

 

 A small backup battery will provide peace of mind, knowing that there is an alternate current path in case of a failed terminal or connection in the main circuit.  But is the benefit worth the extra weight?

 

 Joe

 

 --------

 Joe Gores

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=276838#276838

 

 

 

 

 

 

 

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 ="_blank">www.aeroelectric.com

 ooks.com" target="_blank">www.buildersbooks.com

 et="_blank">www.homebuilthelp.com

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 le, List Admin.

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 -List" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List

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      [quote][b]

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Dec 09, 2009 10:28 am Post subject: Dual Battery Contactor

At 11:00 AM 12/9/2009, you wrote:

 	  Quote: 	
		  

 > "Two heads are better than one and one good battery and two 

 alternators are better than 2-3 batteries any day."  And Bob 

 Nuckolls replied, "Exactly. I'll re-enforce that idea . . . . ."



I am not disagreeing but have questions:



Suppose that it is impractical to install two alternators on an 

electrically dependent engine in a VFR airplane.  If a battery is 

properly maintained and periodically tested for capacity, is its 

risk of failure high enough to warrant  a backup battery?


	


    "Risk of failure high enough" is not quantified.

    Even if it WERE quantified, suppose I tell you that

    configuration A offers a 3.5 x 10^-6 failure rate

    and configuration B is 9.3 x 10^-6 failure rate.



    Hmmm . . . obviously configuration A is the better

    choice.



    Now, suppose the difference in dollars to install

    configuration A versus B is $1600 and perhaps adds

    8 pounds to the airplane's empty weight. How would

    that influence your decision?



    The point is that design goals for your project

    are personal to you . . . a host of trade-offs

    for operation, performance, convenience, weight,

    initial costs, maintenance costs, etc. etc.



 	  Quote: 	
		  What if a cell in the battery shorts out?


	


    Flooded batteries USED to suffer cell shorts . . .

    but only after they had been abused to internal

    self-destruction in ground vehicles. Had those

    batteries been maintained for aircraft service,

    their ability to crank the engine would still

    be quite strong when the replacement decision

    is made. Further, their plates would still have

    a good grip on the chunks of stuff that were

    responsible for shorted cells.



    The RG battery is physically incapable of

    shorting. Active materials in plate pockets

    is held captive by insulating materials. See

    sequence of photos at:



http://aeroelectric.com/Pictures/Batteries/Concorde/



    Here you see cast plates, fiberglas mat material,

    porous jacket, which are placed around the negative

    plate of a "buttered" plate. Alternating (+) and (-)

    plates are sorted, stacked and weighed to match

    cell-to-cell capacity. Finally, matched stacks are

    installed in a battery case ready to attach inter-

    cell connectors. There's no way that any (+) plate

    is going to become shorted to a (-) plate in

    any cell.

 	  Quote: 	
		     Will the alternator keep working?  If no, then will the battery 

 still have enough voltage and contain enough energy to supply the 

 ignition system until a landing can be made?  I assume yes, but do not know.


	


    If it DID happen, the alternator would go into

    current limited full output which would destroy remaining

    "good" cells in what has to be an abused and flooded

    battery. Since you're not going to use a flooded

    battery . . . and you're going to implement a

    battery maintenance program . . . shorted cells

    are of zero concern.



 	  Quote: 	
		  A small backup battery will provide peace of mind, knowing that 

there is an alternate current path in case of a failed terminal or 

connection in the main circuit.  But is the benefit worth the extra weight?


	


    What are you willing to "pay" for peace of mind?

    None of us can properly advise you in that

    decision. What we can offer is the proposition

    that when you assemble a failure tolerant system

    with good craftsmanship, likelihood of more than

    one failure on any single tank full of fuel is

    exceedingly remote.

    Bob . . .

user9253

Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan

Posted: Wed Dec 09, 2009 10:54 am Post subject: Re: Dual Battery Contactor

To Sam and Glenn,

Thanks for your responses.  And Sam, I received your Excel spreadsheet.  I asked the above questions about dual batteries on behalf of my brother who is building a Corvair powered 601XL.  I am building a RV-12 whose Rotax engine has dual independent ignition systems (except for the rotating permanent magnets).  It seems that this is one of those situations where there is more than one way to do something.  If it is someone else's airplane, then 1 battery is enough.  But if you are going to be flying in the plane, then two batteries are better.

_________________
Joe Gores

user9253

Joined: 28 Mar 2008
Posts: 1927
Location: Riley TWP Michigan

Posted: Wed Dec 09, 2009 12:45 pm Post subject: Re: Dual Battery Contactor

Thanks for the reply, Bob.  From your explanation, it seems highly unlikely that the battery will short out.  The alternator is the main power source and the battery is a backup power source (for a limited amount of time).  The Essential Bus switch is the backup for the main power contactor.  The wires and terminals are not backed up, but they can be checked during pre-flight.   	  Quote: 	
		  What are you willing to "pay" for peace of mind? 	


One could ask that same question about a BRS parachute.  The weight and cost penalty are great for a system that will most likely never be used.  But just think of the peace of mind that system offers.  These are personal decisions that each builder has to make.

Joe

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Dec 09, 2009 6:28 pm Post subject: Dual Battery Contactor

At 02:45 PM 12/9/2009, you wrote:

 	  Quote: 	
		  



Thanks for the reply, Bob.  From your explanation, it seems highly 

unlikely that the battery will short out.  The alternator is the 

main power source and the battery is a backup power source (for a 

limited amount of time).  The Essential Bus switch is the backup for 

the main power contactor.  The wires and terminals are not backed 

up, but they can be checked during pre-flight.


	


    Wires and terminals properly installed have about the same

    order of reliability as prop bolts. This means proper tools

    matched to terminals applied to wires that don't wave around

    in the wind. Generally not difficult to accomplish.



    What engine/alternator combination are you contemplating

    and what devices are required for continued engine operations?



 	  Quote: 	
		  One could ask that same question about a BRS parachute.  The weight 

and cost penalty are great for a system that will most likely never 

be used.  But just think of the peace of mind that system 

offers.  These are personal decisions that each builder has to make.


	


    Yup, that's the universe we live in . . .



    Bob . . .

MauleDriver(at)nc.rr.com
Guest

Posted: Wed Dec 09, 2009 7:10 pm Post subject: Dual Battery Contactor

And thanks Bob for teaching so many of us how to use "proper tools  

matched to terminals applied to wires that don't wave around

   in the wind".



"Generally not difficult to accomplish"  Sounds so simple and yet this 

pilot/unauthorized repair station managed to smoke a glider cockpit with 

astoundingly poor wiring.  Yes, a glider.  I'm doing better now.



Thanks!

 	  Quote: 	
		  > Thanks for the reply, Bob.  From your explanation, it seems highly 

> unlikely that the battery will short out.  The alternator is the main 

> power source and the battery is a backup power source (for a limited 

> amount of time).  The Essential Bus switch is the backup for the main 

> power contactor.  The wires and terminals are not backed up, but they 

> can be checked during pre-flight.



    Wires and terminals properly installed have about the same

    order of reliability as prop bolts. This means proper tools

    matched to terminals applied to wires that don't wave around

    in the wind. Generally not difficult to accomplish.

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