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battery capacity

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clemwehner

Joined: 02 Feb 2009
Posts: 32

Posted: Thu Dec 03, 2009 9:28 pm Post subject: battery capacity

How do I determine the minimum battery capacity required for a KF model IV with a 912 and minimal avionics?  



I'm convinced the RG (starved electrolyte) battery is the right type (like the Odyssey), but what size is the right size? We're looking to save weight but don't want to do anything stupid.



thanks,

Clem Wehner

KF IV-912

Oklahoma

_________________
Clem
Oklahoma
Kitfox IV-912, under construction since 1991

lcfitt(at)sbcglobal.net
Guest

Posted: Fri Dec 04, 2009 8:26 am Post subject: battery capacity

Clem,



I bought the PC680 recommended by a friend.  You won't be sorry with an 

Odyssey.  They will hold a charge up to two years and the one I bought was 

fully charged out of the box.  It won't fit in the factory box, but then it 

doesn't require a box.  I made a tray out of aluminum with a velcro strap.



Lowell



---

Guy Buchanan

Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA

Posted: Fri Dec 04, 2009 10:15 am Post subject: battery capacity

At 09:28 PM 12/3/2009, you wrote:

 	  Quote: 	
		  How do I determine the minimum battery capacity required for a KF 

model IV with a 912 and minimal avionics?


	


I've been doing fine with a 20ah battery. I use the Powersonic 

because I'm cheap, but I think the Odyssey has more cranking power.

Guy Buchanan

San Diego, CA

K-IV 1200 / 582-C / Warp / 400 hrs. and counting

_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too.

clint_bazzill(at)hotmail.
Guest

Posted: Fri Dec 04, 2009 3:27 pm Post subject: battery capacity

 I am using a motor cycle battery.  GTX14-BS.  Easy to get anywhere C put the acid in when you buy it.  You can buy them anywhere and they are not expensive.

  

 I change it out at annual  time C every other year.  Haven't had one go bad.  Just about 1500 hours now on 912ULS.

  

 Clint

  

   and I have a lot of avonics.  Model IV-1200

  

  

  

[quote] From: lcfitt(at)sbcglobal.net

 To: kitfox-list(at)matronics.com

 Subject: Re: battery capacity

 Date: Fri C 4 Dec 2009 08:12:36 -0800

 

 --> Kitfox-List message posted by: "Lowell Fitt" <lcfitt(at)sbcglobal.net>

 

 Clem C

 

 I bought the PC680 recommended by a friend. You won't be sorry with an 

 Odyssey. They will hold a charge up to two years and the one I bought was 

 fully charged out of the box. It won't fit in the factory box C but then it 

 doesn't require a box. I made a tray out of aluminum with a velcro strap.

 

 Lowell

 

 ---

Dick Maddux

Joined: 24 Jun 2008
Posts: 516
Location: Milton, Fl

Posted: Sat Dec 05, 2009 5:55 am Post subject: battery capacity

Clint,

  Like you I am also using the GTX14-BS. Bought it at Walmart and seems to be holding up fine after 1 1/2 years but the Odyssey is tempting. I wish it would fit in the battery box.

                                                                                               Dick Maddux

                                                                                               Fox 4

                                                                                               912UL

                                                                                                Milton,Fl   

                                                                                             

  [quote][b]

WurlyBird

Joined: 16 May 2008
Posts: 207
Location: North Pole, Alaska

Posted: Sat Dec 05, 2009 5:15 pm Post subject: Re: battery capacity

I have been having battery issues as well so I am wondering what you guys think about this.  I have the battery which is in the Kitfox catalog and presumably it has been in the plane for 2 years.  Since the temps have dropped down below 55f I have not been able to start the plane cold without jumping it from my truck.  I took the battery to Autozone twice and both times it tested fine, when I throw the charger on it it indicates 90-95% charge after it has sat for a week but it runs out of juice before it gets started.  Today it was 34f wen I was starting the plane and with jumper cables it took about 30-40 seconds to start.  I have seen video of Dave hand propping in the snow with less trouble so I don't get it.  Any thoughts?

_________________
James
Kitfox 3 / 582 / 70" IVO 2 blade GA
50 hrs on the 582 swapping for HKS 700E and Avid Cowl.

Paul A. Franz, P.E.

Joined: 02 Dec 2008
Posts: 280
Location: Bellevue WA

Posted: Sat Dec 05, 2009 6:51 pm Post subject: battery capacity

On Sat, December 5, 2009 5:15 pm, WurlyBird wrote:

 	  Quote: 	
		   



 I have been having battery issues as well so I am wondering what you guys think about

 this.  I have the battery which is in the Kitfox catalog and presumably it has been in

 the plane for 2 years.  Since the temps have dropped down below 55f I have not been

 able to start the plane cold without jumping it from my truck.


	


clip clip



Running the battery to nearly dead then recharging it repeatedly definitely is severe

usage and shortens the battery life. Two years is about the normal life span of these

smaller batteries used heavily, that is from full charge to a very low voltage

condition frequently. So, it is not unreasonable to replace that battery now. But

before you do, make some measurements. With the jumpers connected right at the battery

and while cranking it over measure the voltage. Then do it again right at the starter.

That will determine the voltage drop in the cable. I think that it should not be more

than 2 to 2.5 volts drop. If it is, examine the connections and make a determination

whether your cable is big enough. You didn't say where your battery is located. If it

is in the tail, then the long run means generally you need a larger gauge cable than

for a very short run.



Another thing to consider when sizing a battery for aircraft the starting function is

not generally the limiting factor. It is the time required to complete the operation

running only what's on the essential buss. So, say your minimum essential load is 10

amperes and your minimum required time to complete the operation is one hour then you

will need to have a battery with a capacity of 10 AMP-HRS *BEFORE* it discharges to

the minimum operational voltage. That minimum voltage at the buss is probably around

10 to 10.5 volts or about the top 25% of the battery's capacity so in this case you

would need a battery with a capacity of 40 ampere-hours roughly. I believe Bob

Nuckolls recommends using two batteries, each with about half the required capacity

and changing them out in alternate years so one battery is always under a year old and

the other is under two years.



I didn't verify the numbers quoted above so they aren't precise but you get the idea.

Time to complete your present operation should there be an alternator failure, is

probably more limiting than is cranking capacity.



-- 

Paul A. Franz

Registration/Aircraft - N14UW/Merlin GT

Engine/Prop - Rotax 914/NSI CAP

Bellevue WA

425.241.1618 Cell



Suppose you were an idiot. And suppose you were a member of

Congress. But then I repeat myself.

-- Mark Twain



"It does not take a majority to prevail ... but rather an irate,

tireless minority, keen on setting brushfires of freedom in the

minds of men."

--Samuel Adams



"We, the members of the New Republican Party, believe that the

preservation and enhancement of the values that strengthen and

protect individual freedom, family life, communities and

neighborhoods and the liberty of our beloved nation should be at the

heart of any legislative or political program presented to the

American people."

-- Ronald Wilson Reagan (1911 - 2004)



"Wise politicians will be cautious about fettering the government with

restrictions that cannot be observed, because they know that every break

of the fundamental laws, though dictated by necessity, impairs that

sacred reverence which ought to be maintained in the breast of rulers

towards the constitution of a country."

-- Alexander Hamilton, Federalist No. 25, 1787



"A fondness for power is implanted, in most men, and it is

natural to abuse it, when acquired."

-- Alexander Hamilton, The Farmer Refuted, 23 February 1775



"This Government, the offspring of your own choice, uninfluenced and

unawed, adopted upon full investigation and mature deliberation,

completely free in its principles, in the distribution of its powers,

uniting security with energy, and containing within itself a provision

for its own amendment, has a just claim to your confidence and your

support."

-- George Washington, Farewell Address, 1796

_________________
Paul A. Franz, P.E.
Registration/Aircraft - N14UW/Merlin GT
Engine/Prop - Rotax 914/NSI CAP
Bellevue WA
425.241.1618 Cell
425.440.9505 Office

WurlyBird

Joined: 16 May 2008
Posts: 207
Location: North Pole, Alaska

Posted: Sat Dec 05, 2009 8:20 pm Post subject: Re: battery capacity

 Considering that the charging system was not properly installed when I bought the plane, unbeknownst to me, I have had to finish cross country flights by hand propping and turning on ONLY the intercom in order to utilize the Ipod interface.  Assuming I can avoid any radio/strobe airspace I would say my only power requirement is to aid in starting the darn thing.  But I really like when it starts by battery over hand propping.    



The battery is hanging on the passenger side of the fire wall.

_________________
James
Kitfox 3 / 582 / 70" IVO 2 blade GA
50 hrs on the 582 swapping for HKS 700E and Avid Cowl.

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sun Dec 06, 2009 1:04 pm Post subject: battery capacity

The main requirement for the battery is to start the engine.  If your engine doesn’t have a starter you don’t need a battery at all.  For that reason the size of your starter and the amount of work it has to do should be what governs the capacity of the battery.  

   

This is a bit off line here but certified planes can install electrical load to the capacity of the alternator if they have a load meter if they don’t have a load meter they are only supposed to install electrical load to 80% of the generating capacity.  Many airplanes have plugins for external batteries or power supplies to start the engine…  That saves a lot on weight carried aloft.  

   

My 582 was supposed to have a maximum of 16 Amp continuous generating capacity.  The most load I had installed was for around 8 Amp.  That meant that with everything I had on board turned on I was still only at 50% of my generating capacity.  

   

Noel  

       

From: owner-kitfox-list-server(at)matronics.com [mailto:owner-kitfox-list-server(at)matronics.com] On Behalf Of Clint Bazzill

 Sent: Friday, December 04, 2009 7:53 PM

 To: Kitfox list

 Subject: RE: battery capacity  

  

  

   



  I am using a motor cycle battery.  GTX14-BS.  Easy to get anywhere, put the acid in when you buy it.  You can buy them anywhere and they are not expensive.

  

 I change it out at annual  time, every other year.  Haven't had one go bad.  Just about 1500 hours now on 912ULS.

  

 Clint

  

   and I have a lot of avonics.  Model IV-1200

  

  

  

 > From: lcfitt(at)sbcglobal.net

 > To: kitfox-list(at)matronics.com

 > Subject: Re: battery capacity

 > Date: Fri, 4 Dec 2009 08:12:36 -0800

 > 

 > --> Kitfox-List message posted by: "Lowell Fitt" <lcfitt(at)sbcglobal.net>

 > 

 > Clem,

 > 

 > I bought the PC680 recommended by a friend. You won't be sorry with an 

 > Odyssey. They will hold a charge up to two years and the one I bought was 

 > fully charged out of the box. It won't fit in the factory box, but then it 

 > doesn't require a box. I made a tray out of aluminum with a velcro strap.

 > 

 > Lowell

 > 

 > ---

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Paul A. Franz, P.E.

Joined: 02 Dec 2008
Posts: 280
Location: Bellevue WA

Posted: Sun Dec 06, 2009 2:42 pm Post subject: battery capacity

On Sun, December 6, 2009 1:01 pm, Noel Loveys wrote:

 	  Quote: 	
		   The main requirement for the battery is to start the engine.  If your engine

 doesn't have a starter you don't need a battery at all.  For that reason the

 size of your starter and the amount of work it has to do should be what

 governs the capacity of the battery.


	


That would only be true if your essential load was zero. That is, the case if you

require no power at all to complete a flight operation safely in the event of

alternator or VR failure. Night flight, operation in Class B airspace, or IFR flight 

would certainly have some essential loads for lighting, navigation and communication.

If you don't *EVER* need those, then it is reasonable to declare you have no essential

load. The reserve battery capacity to complete a flight operation safely while

operating the minimum essential load with an alternator or VR failure is usually more

than that required for engine starting.



-- 

Paul A. Franz

Registration/Aircraft - N14UW/Merlin GT

Engine/Prop - Rotax 914/NSI CAP

Bellevue WA

425.241.1618 Cell



In general, the art of government consists of taking as much money as possible from

one party of the citizens to give to the other.

-- Voltaire (1764)

_________________
Paul A. Franz, P.E.
Registration/Aircraft - N14UW/Merlin GT
Engine/Prop - Rotax 914/NSI CAP
Bellevue WA
425.241.1618 Cell
425.440.9505 Office

lcfitt(at)sbcglobal.net
Guest

Posted: Sun Dec 06, 2009 4:45 pm Post subject: battery capacity

This sort of sounds like it is right out of Mr, Nuchols posts of a decade 

ago.  He, at the time, was a regular participant on the Kitfox list and due 

to his urging, I wired in the essential buss and all the trimmings in my 

1993 Model IV.  It sounded like a good idea at the time.  The only thing, 

though, was the need in the 912 installation, to put a dummy load in the 

charging circuit on case you ever shut down the altenator to prevent frying 

the regulator.  I don't understand the circuitry, but that was what I 

understood.



In short, the only thing my essential buss switch served for was as a 

conversation starter as almost everyine that ever sat in the passenger seat 

asked what that switch labeled "Essentail Buss" was for.  I never installed 

the dummy load and my day VFR flying for the 900+ hours the airplane lasted, 

I never had an occasion to need it.



Bob Nuchols is the Guru, but most Kitfoxes do not use an alternator that is 

capable of runaway charging voltages and the need of an alternator switch to 

protect a battery from a runaway alternator.  In my opinion, he might have 

something to say about certified installations and particularly those in 

complex aircraft like the Lancair and some others, but to use much of what 

he recommends in our stock Rotax installations results in way overkill.  For 

some reason, I also prefer circuit breakers to fuses.



Lowell

---

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Mon Dec 07, 2009 5:52 am Post subject: battery capacity

My take on it, after having a look at the schematic, is the voltage

regulator requires some load on it at all times to work properly.  Without

the load if you happen to turn everything off the regulator can overload and

go into runaway.  If that happens with a 9XX and the built in alternator the

answer is simply to switch everything on and unfortunately, replace your

regulator/rectifier as soon as practical.  If you have an optional high

output exterior alternator don't turn anything on because the voltages will

be high enough to fry bacon.



I do have a question I'd like to pose to Msr. A. Bombardier.  Why didn't

they build in a load into the rectifier/regulator?  It would make wiring a

lot easier for amateurs who are more interested in flying



Noel



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

occom

Joined: 26 Aug 2006
Posts: 404

Posted: Mon Dec 07, 2009 2:00 pm Post subject: battery capacity

I would guess that Bombardier didn't build in a dummy load because A) they 

didn't design or build it, B) it isn't necessary when an actual load is 

present  C) the heat generated by wasting 12-16 watts of generated power 

would be damaging to the unit without a constant source of cooling and D) 

because this is the cheapest unit they could find that does the job most of 

the time. (well it's cheap when Rotax BUYS it. No guarantee about when they 

sell it).



I posted a long time ago about how these units regulate and the advantages 

and disadvantages of each. The best by far is the key west unit if you want 

to stick to "official" units. Any unit off virtually any permanent magnet 

alternator equipped motorcycle, scooter, outboard, garden tractor, could be 

used even one from a late model Harley if you are predisposed to Harley type 

stuff.



---

Guy Buchanan

Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA

Posted: Tue Dec 08, 2009 8:15 am Post subject: battery capacity

At 04:39 PM 12/6/2009, you wrote:

 	  Quote: 	
		  Bob Nuchols is the Guru, but most Kitfoxes do not use an alternator 

that is capable of runaway charging voltages and the need of an 

alternator switch to protect a battery from a runaway alternator.


	


For about a year I had my voltage regulator intermittently fail, 

allowing high voltages into the system. The Nucholls "crowbar" 

overvoltage system handled it so well I didn't get around to fixing 

it for quite a while. I finally replaced the regulator with a Key 

West which solved the problem. I built Bob's "simple" Rotax schematic 

which didn't have any of the essential bus stuff, but if I was going 

to fly at night or IFR (I do neither) I probably would.

Guy Buchanan

San Diego, CA

K-IV 1200 / 582-C / Warp / 400 hrs. and counting

_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too.

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Wed Dec 09, 2009 11:58 am Post subject: battery capacity

As far as I know the load resistor is a fairly hefty thing... as electronic

resistors go.  I don't think it can handle anything over 2W and is designed

to pass a lot lower wattage than that.  Without checking I think the

resistor that was on my 582 was around 3.5 kOhm.  That means there is about

.0039A. going across the resistor or .05 W. at stabilized 13.8V.



Noel

--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

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