Battery Life

[OBK!]

I just finished a flight yesterday and noticed that after shutting down the engine, with the master switch still on, and all the electrical loads turned off, that the Gyro was gradually winding down as if I had turned off the master.

Is this the battery quickly running out of energy? How fast does the average piston engine 28V battery last!?

I sometimes like to have a play about (;)), with the avionics(:rolleyes: ), but after yesterday it's made me think, just how long after you've been playing with the COM box, or fooling around with the GPS, do you have until the battery doesn't have enough energy to get the donkey going?

I'm talking average figures here, I know some bats are very nice and last longer than others. Another reason I ask is because come Monday, I'll want to be programming the GPS before my trip to Jersey as a crosscheck for my VOR's as I have heard the plane is a bit temperamental when it comes to NAV equipment. At what time should I stop programming the GPS? I need enough time to be able to create a route and store it, otherwise, it's lost when I turn the bleeder off :mad: !

Cheers
obk

[DasaniMan]

Help us with what type of aircraft you have.

Do you have a vacume gyro or electric driven one?

What type of GPS do you have?

[OBK!]

I am looking for typical figures for a Seneca. Vacum driven gyro.

The aircraft that I was refering to in the original post was a vacum driven gyro, but obviously has one electrically driven one, otherwise I wouldn't here anything :confused:

The GPS is just a Garmin GPS100.

Thanks v.much
obk

[bluskis]

The gyro that was running down was probably an engine driven vac/ pressure gyro.

I have read figures that give 14 minutes as the time the average aircraft battery will continue to power the normal electrical load, following alternator failure.

I don't think that included deice and pitot heat.

If the battery connections fail, the time is much shorter.

Good idea to have a battery powered GPS as a back up for the nav instruments and the DI.!!!

[cwatters]

Not sure about your particular situation but...

Lead Acid batteries don't like being left for long periods unless they are hooked up to a float charger. The fastest way to trash a lead acid battery is to let it discharge. Regular use is best.

[FormationFlyer]

The sadest reflection here is the number of postings who seem unaware that most modern a/c actually use 3 gyro driven instruments - 2 vacuum driven (Ai/DI typically) and one ELECTRICALLY driven (TI/TC).....

To be honest if you a fully qualifed PPL and dont know the answer to which instruments are driven what way then whoever checked you out (CRI/FI) was SERIOUSLY amiss....this info can save you life (depending on the nature of your flying).

Re: Batteries....

anywhere from 30mins-1hr depending on loading with the master on...it is often stated in the POH/FM - again if you havent looked here *first* - or worse still didnt think of looking here first then again you have had duff instruction....

The *best* idea is to have a bloody clue how to navigate instead of w**king over the GPS and failing to look out of the aircraft...


P.S. Compasses dont take electrical power. I can fly a straight line without *ANY* electrics - and indeed proved this recently when I really did have an alternator failure in flight....Maps & a proper Plan dont require power either. What do you do if the GPS unlocks or fails due to bad battery?!?

Pen & Paper...the ONLY way to safely navigate....

[411A]

According to Gill (now owned by Teledyne...and they make the majority of lead-acid batteries for general aviation aircraft in the USA), the 'average' life of a ships battery is three years.

Beyond three years, the likelyhood of battery failure rapidly increases, especially for aircraft that are not flown all that often.

Having said this, have personally seen Gill batteries last seven years.

Change mine after three years....always.

[OBK!]

"The sadest reflection here is the number of postings who seem unaware that most modern a/c actually use 3 gyro driven instruments "

Who said anything about modern and who reflected their sadness in not knowing the TC was electrically driven? :confused: Last time I looked at a relativley new 747, it had EFIS displays (i.e all electric).

"Pen & Paper...the ONLY way to safely navigate...."

Until your pen runs out, and the paper falls on the floor and you have to divert your attention, or you run into a pretty black cloud.

I'll decide how I will navigate, but they don't paint pretty clouds on the map FF, so pen and paper are pretty useless in IMC and if you fly IFR. :hmm: .

"The *best* idea is to have a bloody clue how to navigate instead of w**king over the GPS and failing to look out of the aircraft..."

Oh? So programming the VORs and GPS as backup, and having a direct image of where you are keeps your head in the flight deck? Prior to using GPS/VORDME/RNAV I found that my head was down looking at numbers, figures, magnetic headings, all smudged on a peice of paper, trying to fly the aircraft one handed whilst I drew a few lines on the map to work out how far off track I was, 1 in 60 rule et al. Now, all I have to do is look at VOR/DME and crosscheck GPS with it and I can have my head outside (inside, but looking outside should I say) the cockpit at least 90% of the time, rather than on some peice of paper on my knee.

"'I'll want to be programming the GPS before my trip to Jersey as a crosscheck for my VOR's as I have heard the plane is a bit temperamental when it comes to NAV equipment."

^^^ Maybe you didn't read that sentence FF. ^^^

With regards to the POH, it's kept at the aeroclub, I wasn't going to drive all the way there just to find out, when a there's a perfectly willing and friendly (;) ) community on the internet who can help me out.

Thank you anyway for revealing your emotions and for answering the question...

"anywhere from 30mins-1hr depending on loading with the master on..."

Though you did it in quite a few more words and paragraphs.


L8rs
obk

Thanks 411A, I'll certainly be passing that on to the aeroclub :ok: . DO you happen to know how long it could go in one blast with all the electrics on?

3 years seems ages, just enough time to upload the route into the GPS me thinks! oh...and store it :=

Cheers
obk

[FormationFlyer]

OBK - Think you took things the wrong way a little there - and took a couple of items personally which werent aimed at you. :)

Um. PA34s *are* modern. :) And most secencas do have 3 gyros and the one you heard running down as you turned the electrics off will be the TC - turn the electrics on then off without the engines ever running and thats should prove it.

The paper I refer to is called a MAP. A legal requirement for navigation. I never impled anything more than that - there again I never implied much.... Oh and do you not carry more than 1 pen? I carry 3...What I was getting at is that regardless of what NAV aids you use you should always draw a line on a map. Thats all I am saying. :)

In terms of running into black clouds - inadvertant IMC does not happen. Total myth. To get that close to a cloud to start with proves a serious lack of judgement/airmanship - unless you are intending an IFR flight anyway. In which case it didnt matter anyway.

Please dont confuse IFR with IMC....

Talking of IFR - as an instrument instructor....dont you write down clearances, not down times overhead at various waypoints etc...or do you rely on the GPS battery to remember all this information - not being provocative - just curious....anyway..GPS doesnt cover fuel burn and whats left in the tanks does it?

Writing LEGIBLY is an important part of basic nav training - I dont let my PPL/IMC students get away with it - so why did you go flying with something that could smudge? I was not dictating methods of navigation to you....I think you misunderstood - partly caused by me failing to fully articulate what I meant and leaving just a glib comment....and having a stab at others who appear to think lookout is optional.....apologies.

If the plane's nav equipment is that bad I think its time to find another a/c to hire, or if you own it - get it fixed. Personally I hate flying with defective equipment - there is little excuse for it....Having said the nav equip can be dodgy do you think it would be a fair defence to say you got airbourne with GPS as a backup - because if the nav aids did play up you would then be using GPS as a primary source of navigation - as you appear (i did say appear) to have an aversion to nav logs/maps? (please correct me...)

And my congratulations to you - someone who uses the GPS in the way it should be used in a cockpit - i.e. heads outside 90% - I agree fully! :ok: All respect to you from me.

EFIS is electronic - not electric. If we are going to be pedantic ;)

Please forgive me for possibly venting frustration with some pilots - it wasnt meant at you directly- but recently I have started thinking that a large number of pilots appear to feel that toys and gizmos are more important that basic navigation & airmanship (i.e. lookout)....thats all. Sorry if you felt I was aiming it directly at yourself....I dont know your flying and most certainly was not making an assumption about your level of airmanship etc....apologies for any comments taken this way.....

With regard to electonic nav aids....I do use GPS,VOR,DME,NDB,RNAV - VFR or IFR. But I use them as you suggest - as a quick heads in check of how things are going - rather than as a replacement for the outside world!

[bluskis]

OBK's post stated he had shut down the engines, and turned off all the electrical loads, but had left the master switch on. This would mean the electrical gyros were still powered. He did not state which gyros were running down, so the inference to draw would be that they were the vac driven ones, now deprived of their energy source.

His second question was, how long does a battery last before it 'runs down', by inference after the alternators have ceased to charge. The answer is not very long, and your POH won't be able to tell you because it doesn't know the state of your battery to start with, and doesn't know what electrical equipment has been added, or removed since the airplane was new.So if you are in the air make plans to land asap.

He mentioned ' before it stops the donk'. Fortunately as 'the donk' has magneto ignition, it wont stop just because the alternator/battery/wiring has failed/partially failed.


What has looking out and using a GPS got to do with each other?

In event of an electrical supply failure, and assuming you are on a leg of significant distance rather than in your local area, is to turn off everything you can safely do without, and reserve any remaining power for the essentials to come.

Navigating without aids would not be the best way to cope with the situation, particularly if out of sight of the surface, or at night. Using a standby GPS allows most of the avionics to be turned off to preserve power for the radio calls ahead.

Using what is available is called CRM.

[411A]

OBK!

Different sized batteries/condition/amperage draw of components...well the list is long indeed.

Do recall from years ago was flying an S35 Bonanza at night, all the radios going (including DME, but no transponder in those days) and after an alternator 'failure' was still able to read the instruments after one hour, approximately.

Must have been a pretty good battery.

NB. The alternator 'failure' was due to the fact that the pilot forgot to switch on same.
When corrected, the ammeter pegged at 100 amps.
Big red lights....fortunately no failures, all instruments were illuminated red....ah, the good 'ole days.

[OBK!]

I think I might aswell get at least one of the rubber bands wound up and supplying amps before I jump into programming the GPS then! :O

Bluskis, regarding the donkey, I was just wondering how long before the battery wouldn't have enough power to get it going, rather than keep it going as I remember one time I had been contacting ground at EMA for startup, but after 5 mins waiting for startup clearance, listening on the COM radio, the battery only just had the energy to swing the prop over, I was lucky that day :ouch:

Thanks again folks, I am now even more wiser. That's what I love about this hobby, you never stop, it's an inifinate learningn curve.

Chow
Obk

[FormationFlyer]

Hi all..cold light of day less tired now...apologies for talking bollocks for some reason....

Blueskis - you are right he did say with the master still on it sounded like gyros running down - however my statement about pilots not knowing whow which instruments are driven in what way still stands - if you dont know you shouldnt be flying that aircraft type. It means that you do not have enough information on the type of aircraft you are flying. Thus (more likely than not)your conversion/familiarisation training was defficient - a sad reflection on the instructors involved rather than the pilot.

Its like hydraulic & vacuum systems - on some twins the vac pumps & alternator are on a single engine - not both as in the case of the vast majority of senecas - failure of this engine could prove fatal unless you fully understand the implications.

Regarding battery life - you obviously havent read some POH - where it *is* stated for a good many a/c out there - for instance PA28s actually have an entry in them. Now whilst I agree that the unknown factor is the condition of the battery it is none the less still stated - and afaik the battery will be tested on maintenance to ensure that it will provide this performance - i believe this is a CofA issue - but must confess I dont know and am now speculating....

p.s. I have nothing against GPS. I understand cockpit resource management...It is refreshing to know that there are still pilots out there that look out of the window...the relationship between the two - is that too many pilots love watching their moving map GPSs - rather than looking out of the window. This isnt speculation - im a flying instructor and *know* this is the case having witnessed it a number of times....and....75% of qualified pilots I observe fail to maintain adequate lookout - especially in the climb & manoeuvring. The problem is that many pilots do not do proper planning - instead they merely program up the GPS...OBK obviously does not fall into that category and I applaud him for being one of the pilots whose flying is obviously more 'professional' than most.

However, i do apologise for getting the soap box out on an unrelated topic....

[Penny Washers]

If you suspect the battery, check the generator. I can never understand why the battery has to have a cap check so regularly while the generator seems to be allowed to go on until it fails.
If your battery is well up, then essential instruments should continue to work for half an hour. That doesn't mean that the batt would then have enough go in it to deal with an engine start.
The GPS 100 does have integral batteries in it - at least, mine does. A useful standby!

[A and C]

Following a major avionic upgrade on my Robin I checked the life of the battery first the whole electrical system was run for 5 min and then the system was "load shed " leaving only the HSI , GPS , NAV/COM 1 and the transponder running in avionic stack.

The nav and cockpit lighting was running along with the T/C and all the cockpit indicators.

After 40 min RMI , ADF and DME were switched back on for 5 min and all functioned for the test.

The test was ment to simulate an alternator failure in IMC , the load shedding drills being done and then the minimum equipment being used for an instument approach.

The battery was fully charged and the OAT was about 5 C.
I would guess that the battery had about another 5 min before things started to fail and I suspect that the COM TX would be the first thing to fail.

[Keef]

It depends very much on what's turned on, as several folks have said. With a bare minimum of one NAV and COM plus the TC and basic instruments, you can keep going for a surprisingly long time.
If you leave your transponder on, it's a lot less, and if you use pitot heat it's a very short time indeed. In effect, you don't need pitot heat at all, because you'll be out of power so quickly you might as well not have bothered.

I had an alternator failure in IMC (in MiG alley) some years ago, and scary it was! That was in a C172.

I "load shed" quickly, but had to keep some stuff on to navigate with. The COM TX stopped after about 10 minutes, but by then Gatwick Approach knew what was up, and the receiver carried on fine so I just followed instructions.

An excellent controller coordinated a speedy diversion, and I was on the ground at Biggin 15 minutes after the alternator went "offline", still with a working VOR and a COM receiver, plus the electric turn coordinator. But I was very glad the AH and DI were vacuum operated.

It was a flapless landing. No drama. An engineer at Biggin fixed the problem in about five minutes, used a "trolley" to restart, and we were on our way.

I wouldn't want to do that too often, though.

[OBK!]

Thanks AC some nice test results you got there :ok:

obk

[Fuji Abound]

Of course each C of A renewal the battery load has to be proven to comply with the POH and so recorded. Equally it may be some time since the last check.

[604guy]

Always interesting to see how we can digress in our answers and I am as guilty as the next person!

How long will my battery last you ask? Find out the ampere hour rating of your battery, add up the amperage draw of the components you have on and the answer becomes a simple arithmatic question. That of course assumes a battery at 100% charge and effciency at the outset. That would also not ensure that you can energize high draw items such as a starter much below battery peak. So many other factors come into play i.e. how much cranking of the starter is going to be required to start the bloody thing due to pilot technique, engine condition, ambient temperatures etc.

It is a good exercise though to have an idea of the amperage draw of all various systems on your aircraft. On that dark and stormy night when the gods are conspiring against you and you find yourself in an emergency and down to battery power you will be very glad that you have gained that knowledge. You can be surprised that the one item that you thought would be a good idea to get you to some tarmac uses much more power then you had thought and you in fact might be better off using two of something else.

As an aside, I too was pleased to see that you refered to using the GPS as a backup to other items. It indicated to me that you were using the resources available to you whether it be a full blown FMS system or a map. Over the years as I have flown with some new hires I have sometimes seen an over reliance on the whiz bang gadgets that have entered our cockpits. Don't get me wrong I use them and enjoy all of them as much as any but don't forget the basics. When I look over at their side of the office and see that not all is as it should be and I reach down and make the FMS readouts suddenly go dim and then look at him/her and say "ok, where the hell are we and how do we get there now." it drives the lesson home....use all resources available to you.

Also, if you are going to go out ahead of time and start one fan to provide power while you program things might I suggest you taking an extra pair of eyes with you. You will have your head down and those eyes could keep a lookout for things such as your a/c moving, vehicles, stray people etc. I have seen the consquences of someone not doing that and it's not pretty.

Regards,
604guy

[gasax]

The battery in a PA34 is a Gill G35 or G35S.

It has a 30 minute capacity rating of 40 amps. This means it will if fully charged deliver 40 amps for 30 minutes and the cell voltage will still be more than 1.75V per cell, whilst at 25 deg C.

Gill state that their batteries remain serviceable until they can only deliver 80% of that 30 minute demand.

So you have at the very minimum 16 amp/hours of supply - at the end of which your battery is still producing a significant level of power but the remaining ouput is very dependent on its condition.

If you load shed thoroughly your battery will last considerably longer than the fuel in your tanks. Continue using the pitot heat and all the lights 30 to 60 minutes.

And battery capacity was added to the LAMS schedule as an annual check - presumably because so many people think you cannot fly without electricity?