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Basic Battery Wiring
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doug kandle

Joined: 09 Jan 2006
Posts: 33
Location: Boise ID

Posted: Sun Oct 29, 2006 9:33 am Post subject: Basic Battery Wiring

I have attached a picture of what I plan to do to wire my battery power in my 701.  This is kind of the way that my Cessna is wired.  Is this similar to what others are doing?



Specifically- is the battery relay required?  It seems like a good idea.

My battery is behind the seat (where ZAC recommends) and I plan to put the solenoid there too.



I only have the built in alternator in the Rotax, so no additional alternator (30A max).



This plane will only be used for day, VFR, ground always in sight flying. So I'm not too worried if all of my electrical fails.  I'm not going to worry about two-point failures (electrical and coolant for example).



Do any of you see any problems with this setup?

701PowerWiring.jpg

Description:

Proposed power wiring diagram

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15.73 KB

Viewed:

783 Time(s)

craig(at)craigandjean.com
Guest

Posted: Sun Oct 29, 2006 10:45 am Post subject: Basic Battery Wiring

If you haven't already you might ask this on the AeroElectric list. And buy

Bob Nuckolls' book.



-- Craig

planejim(at)bellsouth.net
Guest

Posted: Sun Oct 29, 2006 2:43 pm Post subject: Basic Battery Wiring

Doug,



FWIW, a couple of things to think about in reference to your "wiring 

diagram". Remember this is a Rotax  alternator system with a yellow output 

wire and ( ? don't have the other color marked on my diagram ) ? output wire 

going to the "G" terminals of the Rotax supplied Regulator. This is per the 

suggested electrical system wiring diagram I received with my kit from ZAC. 

This is probably different than a Cessna or Piper which uses a different 

regulator. I've designed the electrical systems ( all basic 12 volt DC ) 

systems for several aircraft including a couple of my own including my 

current Rotax 912UL powered 601HD. They have all worked well with one 

exception which I will discuss later.



Let me suggest a few items for your consideration based on the diagram you 

provided:

1) Don't have your starter wire - which goes from the Batt. to the heavy 

contacts of the Starter Relay - go through the Batt. Sol. The starter draws 

a heavy current. I would consider having the heavy Starter wire come 

straight off the "+" terminal of the Batt to the Starter Relay then on to 

the starter.

2) Since the Alt built into the Rotax puts out about 14 amps max. ( as I've 

been told ) I don't think you need a 30 Amp main. ZAC only provided a 15 AMP 

breaker with my kit and that is what I've used for 10 years and 532 hours 

with no problem. Also put the Main ( 15 AMP ) breaker between the Batt Sol 

and the Main Buss.

3) Have the Rotax Regulator output ( it is the B+ terminal on the 

regulator ) go to the "+" terminal of the battery. This way your onboars 

aircraft systems draw from the Battery via the Buss and the Alternator 

charges the Battery. There is another thing that the Rotax diagram does - a 

short jumper goes from the "R" terminal of the regulator to the B+ terminal 

of the Regulator. Also, I was advised to put a load on the "L" ( lighting 

coil as Rotax calls it ) to make the regulator work correctly when there is 

no other load. They stated that you can use a light bulb or do as I did and 

put a 48 OHM load between the "L" terminal and the Main Buss. It has also 

worked fine for all these years.



Now for that one glitch I had. When I first put the plane in service, and 

didn't run it for a week or so, my battery would be very weak. I thought I 

had a bad battery. It turns out there was a flaw in the ZAC wiring diagram. 

The wire from the "C" terminal of the regulator orignally went from the "C" 

terminal to Battery side of the Batt. Sol. This caused ( because of the 

internal wiring of the regulator ) to put a 30 to 50 milliamp continuois 

drain on the Batt. What I didn't pay enough attention to was that there were 

two different ZAC wiring diagrams. A fellow in Austrailia discovered the 

problem on his airplane and put the word out and Jim Weston - a fellow 601 

builder - told me about it. Guess what one of the differences was? the 

second diagram called for routing the "C" terminal wire to the other side of 

the Batt. Sol. So that the connection to the Batt. was only made when the 

master is on. I rewired it and am still using ( this is a true statment - 

honest ) the same Concord GR-25 Battery which is almost 11 years old and 

still starts my 912 fine. That is ALL I use it for so I don't worry about it 

failing in flight. As you say day VFR only with full ground contact. That's 

my kind of flying. I have all the ratings but I don't use them in this 

airplane!



If you don't have a ZAC supplied Rotax 912 ststem wiring diagram, I suggest 

you ask them for one. Good luck with your electrons.



Jim Hoak

---

p.mulwitz(at)worldnet.att
Guest

Posted: Sun Oct 29, 2006 3:13 pm Post subject: Basic Battery Wiring

Hi Doug,



I am curious why you consider coolant failure in the same sentence as 

electrical failure.  It seems to me that coolant failure is fatal and 

you must land immediately after turning off the engine.  Electrical 

failure is not much trouble at all so long as you can navigate your 

way to a suitable airport.



Paul

XL fuselage

 	  Quote: 	
		  This plane will only be used for day, VFR, ground always in sight 

flying. So I'm not too worried if all of my electrical fails.  I'm 

not going to worry about two-point failures (electrical and coolant 

for example).



Do any of you see any problems with this setup?


	


-

doug kandle

Joined: 09 Jan 2006
Posts: 33
Location: Boise ID

Posted: Sun Oct 29, 2006 4:14 pm Post subject: Re: Basic Battery Wiring

 	  p.mulwitz(at)worldnet.att wrote: 	
		  Hi Doug,



I am curious why you consider coolant failure in the same sentence as 

electrical failure.  It seems to me that coolant failure is fatal and 

you must land immediately after turning off the engine.  Electrical 

failure is not much trouble at all so long as you can navigate your 

way to a suitable airport.



Paul

XL fuselage



	




A coolant failure is very serious, but I am not going to do a two point failure analysis, only single point failures.  If the coolant system fails, then my EIS will detect it and I'll land.  If, however my electrical system fails, then (before I land) my coolant system fails, I will have no way to detect the overheating condition until the engine begins to loose power.   This is an event that I feel is so remote that I am not going to deal with in the electrical system.

craig(at)craigandjean.com
Guest

Posted: Sun Oct 29, 2006 4:14 pm Post subject: Basic Battery Wiring

Actually I read somewhere that the Rotax 912 can run at 50% power with

complete loss of coolant.



-- Craig 



--

doug kandle

Joined: 09 Jan 2006
Posts: 33
Location: Boise ID

Posted: Sun Oct 29, 2006 4:24 pm Post subject: Re: Basic Battery Wiring

 	  planejim(at)bellsouth.net wrote: 	
		  Doug,

1) Don't have your starter wire - which goes from the Batt. to the heavy 

contacts of the Starter Relay - go through the Batt. Sol.   I would consider having the heavy Starter wire come 

straight off the "+" terminal of the Batt to the Starter Relay then on to the starter.

2) Since the Alt built into the Rotax puts out about 14 amps max.  I don't think you need a 30 Amp main. ZAC only provided a 15 AMP 

breaker with my kit and that is what I've used for 10 years   Also put the Main ( 15 AMP ) breaker between the Batt Sol 

and the Main Buss.

3) Have the Rotax Regulator output ( it is the B+ terminal on the 

regulator ) go to the "+" terminal of the battery. This way your onboars 

aircraft systems draw from the Battery via the Buss and the Alternator 

charges the Battery.

Jim Hoak

--- 	


Jim:



[ I noticed an error in my drawing shortly after I posted it.  I don't want the starter relay to be powered from the avionics bus, since I want to be able to have the avionics powered off when I crank/shutdown the engine. ]



Attached is the wiring diagram from the Rotax manual that came with my engine.  It shows a 30 A fuse.  I shouldn't be using any where near that much for my few instruments so I'll go with your suggestion of a 15A.  The Rotax manual says that the alternator will put out 28A max.



If I don't have the starter go through the master relay, then the engine can be cranked even though the master switch is off.  This seems too dangerous to have the starter switch hot even with the master in the off position.



If I connect the alternator to the battery, and the instrument bus to the battery, then how do I disconnect the alternator from the bus so that everything is powered off of only the battery in the event the alternator malfunctions?  Don't I need several switches/circuit breakers?  I need to (a) isolate the alternator (alternator breaker/switch), (b) remove power from all of the avionics while I crank & shutdown the engine (avionics master switch), and (c) I need a way to turn everything off (the master).

RotaxManualSnip.jpg

Description:

part of page from Rotax 912S Install Manual

Filesize:

28.1 KB

Viewed:

661 Time(s)

craig(at)craigandjean.com
Guest

Posted: Sun Oct 29, 2006 4:57 pm Post subject: Basic Battery Wiring

Run the starter directly from the battery through the starter's contactor

but power the coil in the contactor from the switched buss. So the starter

is fed directly but the contactor can't close unless the master is on.



-- Craig

doug kandle

Joined: 09 Jan 2006
Posts: 33
Location: Boise ID

Posted: Sun Oct 29, 2006 6:08 pm Post subject: Re: Basic Battery Wiring

 	  craig(at)craigandjean.com wrote: 	
		  Run the starter directly from the battery through the starter's contactor

but power the coil in the contactor from the switched buss. So the starter

is fed directly but the contactor can't close unless the master is on.



-- Craig 	


Craig:

My battery is behind my seat, 6 feet or so aft of the firewall.  I don't want any uncontrolled heavy wire to go from the battery area to the firewall (to limit the amount of cable that can cause me real problems if it shorts out).  So, I want my master solenoid to be right next to the battery.  If I connect my starter to the battery, without passing through the master solenoid, then I would have to run an uncontrolled  heavy wire from the battery to the engine this would completely negate any advantage of having the solenoid next to the battery.



In a forced landing you turn off the master so that there will be less chance of any sparks starting a fire.  I want all of the electrical system possible to be inert if I ever have to do a forced landing.



I just double checked the drawings for my Cessna 206 and it passes the starter current through both contactors.  Since the part I am using is identical (I believe) to the one in my Cessna, it should be able to handle the current.

planejim(at)bellsouth.net
Guest

Posted: Sun Oct 29, 2006 6:38 pm Post subject: Basic Battery Wiring

Graig,



I agree. That was going to be my reply. Run only the started control through 

the Batt sol.



Jim Hoak



---

craig(at)craigandjean.com
Guest

Posted: Sun Oct 29, 2006 7:11 pm Post subject: Basic Battery Wiring

Sounds like a sound line of reasoning. I checked a few of the AeroElectric

schematics and they run the starter through the master contactor. It just

isn't my first choice. Where did you buy the master contactor?



-- Craig

doug kandle

Joined: 09 Jan 2006
Posts: 33
Location: Boise ID

Posted: Sun Oct 29, 2006 7:23 pm Post subject: Re: Basic Battery Wiring

 	  craig(at)craigandjean.com wrote: 	
		  Sounds like a sound line of reasoning.

Where did you buy the master contactor?

-- Craig 	




Aircraft Spruce P/N 111-226, $18.90

craig(at)craigandjean.com
Guest

Posted: Sun Oct 29, 2006 7:43 pm Post subject: Basic Battery Wiring

Hmm, not a lot of info in the catalog. Are there any useful marking on the

contactor itself? Or did it come with a spec sheet?



-- Craig 



--

jhstarn(at)verizon.net
Guest

Posted: Sun Oct 29, 2006 8:45 pm Post subject: Basic Battery Wiring

Master contactor---Starter Relay---Starter Solenoid--- "A Rose by any other 

name...".

Aircraft Spruce, page #407, P/N 22735, $9.65. Even if you buy it elseware 

get a FREE ACS catalog. It has a LOT more than pieces & prices... in 

building the info it contains is....priceless.  KABONG Do Not Archive



---

Afterfxllc(at)aol.com
Guest

Posted: Mon Oct 30, 2006 1:35 am Post subject: Basic Battery Wiring

In a message dated 10/30/2006 1:08:31 AM Eastern Standard Time,  jhstarn(at)verizon.net writes:

  

  

  

  

  

 Master contactor = continuous 

 Starter Relay = intermittent

 Starter Solenoid = intermittent

 

  

 Looks like a duck, quacks like a duck, walks like a duck .... still might  not be a duck

  [quote][b]

s.c.richards(at)homecall.
Guest

Posted: Mon Oct 30, 2006 3:36 am Post subject: Basic Battery Wiring

Doug

I have put the Master Contactor Adjacent to the battery especially as it is 

in the rear of aircraft & fed the starter solenoid through this. The 

essential supplies bus has been fed from a 10 Amp fuse adjacent to the 

battery. so Heavy wiring can be Isolated by the master switch

Personally I would only connect the starter solenoid directly to the battery 

if both were firewall forward & adjacent I would then route other supplies 

via a 30 amp fuse adjacent to the battery & via a master isolating switch.

    I believe it is possible to get a remote mechanically operated battery 

switch  (Used on boats & racing cars I believe) as the battery contactor 

must be continuously rated and consumes approx 1 amp

do not archive

Clive Richards G-CBDG

---

Trainnut01(at)aol.com
Guest

Posted: Mon Oct 30, 2006 3:44 am Post subject: Basic Battery Wiring

OK but if you do not run the starter wire through the main contactor next  to the battery, and you should (God forbid) have a serious accident,  then you are dealing with a high amperage wire run from the battery,  through the cockpit, into the engine room and you've got no way to disconnect  it.  If debris or some piece of wreckage happened to cut into the  insulation on that wire you might find yourself sitting on the equivalent of an  arc welder that you can't turn off . I don't even want to think about what  would happen if we add a broken fuel line to this problem. Seems to me that  main contactor should shut off ALL electrical power except maybe a one amp (or  less) breaker protected circuit to provide memory power to the avionics.

 Carroll Jernigan

  

 do not archive

  [quote][b]

Afterfxllc(at)aol.com
Guest

Posted: Mon Oct 30, 2006 8:20 am Post subject: Basic Battery Wiring

Carroll,

  

     Almost every aircraft with a battery is wired with  a master contactor somewhere near it... If you are worried about some  freak thing happening then run the wires thru a PVC pipe or something. Bottom  line is that if you don't put the master contactor by the battery you are  creating a bigger hazard than you are trying to avoid.

  

 do not archive

 Jeff

  [quote][b]

Trainnut01(at)aol.com
Guest

Posted: Mon Oct 30, 2006 9:17 am Post subject: Basic Battery Wiring

Jeff

 Sorry I guess I didn't make my self clear. (My wife says that I never do)  What I was trying to say was that we should not bypass the master contactor  with a starter circuit main power feed going directly to the engine compartment.  The master contactor should be just that, the Master. When that contactor is  open there should be no current available to any electrical  circuit anywhere in the aircraft. The possible exception to this is a  circuit to the "always hot buss" to power the clock and other avionics memories.  Even here I would use the lowest     circuit breaker  rating I could get away with, and mount it as close to the battery as  possible.

 Back in the sixties when I was learning to fly, my instructors always  stressed that during a forced landing you should always turn the mags,  fuel and master switch off (before touchdown if possible) to  reduce the chance of a post cash fire. If you have bypassed the master  contactor with a starter cable (or anything else) you can't turn if off.

 I really think we are both saying the same thing.

 Carroll Jernigan

  

 do not archive

  [quote][b]

jhstarn(at)verizon.net
Guest

Posted: Mon Oct 30, 2006 10:43 am Post subject: Basic Battery Wiring

ACS page #407 right above the starter  relay #22735 is a master relay #111-226. The #22735 is for "intermittent duty"  (like cranking the engine) and the 111-226 is for "continuous duty" for allowing  ANY current to flow from the battery. Maybe I should have left the word "master"  off the "contactor" reference. As I said the information in a ACS catalog  is... priceless.

 When using a catalog it would be  helpful to know that looking up: contactor, relay or solenoid should  take you to the page that has what your looking for.  Do Not  Archive

 [quote]   ---

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