Dafydd Llewellyn Posted October 21, 2014 Posted October 21, 2014 Thanks, Don - that's an interesting slant on it, and it makes sense. I wonder whether there are others with experience on these aspects?
jetjr Posted October 21, 2014 Posted October 21, 2014 This topic has come up a few times - DO NOT USE Lithium ION batteries in aircraft. Pretty sure no one would recommend it. No doubt the odd well informed tech can make them work but there is a risk of thermal runaway and the problems described. Even in RC world they are known danger. Lithium IRON or LiFe are very different thing, dont taint one with results from the other. Not saying rush out and buy one but they are solid technology and steadily coming through with safe circuits built in to work in aircraft systems. Who knows maybe our aircraft charging systems might need to be upgraded to suit with a real regulated altenator.....hang on they already sell them! I echo Dons comments, using battery only power in Ipad does make them run much hotter. Risk of problem in phone and Ipad is linked to battery size - very small. Not many runaways and with laptops, phones and ipads included they have sold a few.
Tex Posted October 21, 2014 Posted October 21, 2014 Someone threw that months Sport Pilot mag out in my house Anyone post it up somewhere? It was an interesting article - I used a LifePo in my aircraft for over a year (582 Rotax). No issues. I regularly flew for over two hours and as I had plenty of experience using LiPo elsewhere and had a disconnection switch right beside the battery (which I disconnected after use to prevent parasitic drain); I regularly checked the battery temp - not once did I ever feel ANY temperature rise. If anything I was usually concerned it was too cold. Voltage never exceeded that the previous Lead Acid battery reached when in use. I read a fair bit about the Ducati charging system after I read Ed's article - as mentioned above, I understand it is the same as used on the bikes... I lack the experience of Ed of course. None the less: these batteries are volatile but I didn't think that the testing Ed did was a true replication of the charging system (particularly the regulator/rectifier) under normal operating ranges. Would be happy to be corrected on that but you will need to post the article to prove it I think Ed's tests were done on LifePo4.
David Isaac Posted October 21, 2014 Posted October 21, 2014 Isn't this a classic case of blame the product when the real problem was incorrect installation and charging setup. If you install in accordance with the specified charging and housing requirements why wouldn't they be safe?????? More importantly install a LiFePO4 battery with correct charging circuitry or DONT install it at all. 3
eightyknots Posted October 21, 2014 Posted October 21, 2014 Dafydd,I have a fair bit of experience with iPads both the full size and the mini (but not the newish "Air"). Operating the iPad on battery only (not connected to 12V power) results in the iPad getting quite hot as the battery discharges during a flight. The heat issue can be exacerbated in a low wing by hot sun and in any aircraft possibly by the device holding the iPad. A very hot iPad will turn itself off and is then unlikely to catch fire. The heating up can be mitigated by exposing it to ventilation and avoiding direct sunlight. However, in my experience, operating the iPad with it plugged in to a 12V supply results in the iPad not getting hot. I don't know for certain the electrical theory on this but my guess is that if the battery is close to fully charged before the flight commences, then the iPad will not accept charge and, because the iPad is being fed at least 2 Amps from the aircraft there is no discharge from the battery. My conclusion - valid or not - is that running the iPad plugged in to the 12V supply practically takes the battery out of the equation. I would welcome my unscientific analysis above being thoroughly questioned and if wrong, corrected. Anyhow, if it got really, really hot, you could always chuck it overboard and hope it doesn't end up parting the skull of a wandering sheep or start a bushfire. Don Don, your analysis is good. When the ipad operates from an external supply there is no current being drawn from the battery (if it is fully charged) or current is supplied to the battery (if it was partly charged at the outset). If you're using the ipad solely from the battery supply, the current drawn from the battery is pretty high, enough to increase the battery's temperature noticeably. If the screen brightness is high, as is likely to happen in an aircraft, the current drawn from the battery is near or at its peak. The battery then becomes significantly warmer. Your idea of running from the 12 volt supply sounds the safest option to me. 2
Bruce Tuncks Posted October 21, 2014 Posted October 21, 2014 Great forum here to pick up on details, thanks guys. But here's my understanding of what those capacitors do: The current into a capacitor I=C*dV/dt So a vertical voltage spike with dV/dt= infinity will cause an infinite current which can't happen. In practice the input current is limited and therefore dV/dt is limited to= I/C which gets smaller as C gets bigger. An infinite size capacitor would have zero voltage ripple at its terminals. I think of the capacitors as like little rechargeable batteries and it takes time and current to change their voltage, but I guess this is a bit simplistic. And Andy I agree with you about "lithium" motorbike batteries. I saw one which was packaged like an ordinary battery but it was far too light to have much in it and just what electronics it had built in was unclear. But an ordinary person could easily swap one of these for a similar-looking battery. We sure need to warn people to stay clear of these things until a lot more is known. Wouldn't it be wonderful if CASA did some testing, instead of spending their time checking on just what photos are in some file in some Canberra filing cabinet. Well we can dream huh. regards, Bruce 1
Rolf Posted October 22, 2014 Posted October 22, 2014 Even using the saver LiFePO4 batteries You will still be playing with the fire. These batteries have quite a different charging regime compared to Lead Acid batteries and require a balacend charge like the LiPo batteries. Without a balanced charge You will never know if the battery is fully charged and also risk overcharging of individual cells which can result in fire. Another problem of this battery chemistry is that unlike Lead Acid batteries where the voltage can be used as an indicator for the state of charge, LIFEPO batteries maintain their voltage almost constant and then drop dead in a flash possibly at a time when you last need it. If anyone is still tempted at least upgrade your charging circuit by someone who understands batteries, anything else is playing with fire 1 1 1
David Isaac Posted October 22, 2014 Posted October 22, 2014 Why would anyone change any battery technology in anything without assuring themselves that the charging regime is compatible ..... profound stupidity, let alone unprofessional. Makes you wonder about the amateurish approach by some aircraft owners. Don't they value their life? 2
Keith Page Posted October 22, 2014 Posted October 22, 2014 Why would anyone change any battery technology in anything without assuring themselves that the charging regime is compatible ..... profound stupidity, let alone unprofessional. Makes you wonder about the amateurish approach by some aircraft owners. Don't they value their life? ....................................and kit constructors .. Regards KP.
flying dog Posted October 22, 2014 Posted October 22, 2014 To establish a baseline in controlled environment there is on problem.
Dafydd Llewellyn Posted October 22, 2014 Posted October 22, 2014 What I get from this, is stick to lead-acid for the main aircraft battery; and where you have a low-power device such as an Ipad mini, it needs to be (i) in the shade, (ii) supplied with cooling air - and that may mean air that has been run past a freezer brick - and (iii) I'm going to put a temperature sensor on the back of the thing and see whether Don Ramsay's notion is correct.
nomadpete Posted October 22, 2014 Posted October 22, 2014 Dafydd Can I suggest that you allow space within your metal encapsulation for the air to be drawn across the back of your IPAD? Logically, a charging source should reduce the heat generated within the device. Avoid the cheaper chargers. Also, avoid using a car type cigarette lighter socket. These are not reliable.
Guest Andys@coffs Posted October 22, 2014 Posted October 22, 2014 So depending on the size of the iPad and it's specific generation will be its current consumption. Full sized iPad 3 (43Whr battery) with an in plane 1amp 5v (5w) charging circuit will require the battery to suppliment the charging cct because the iPad turned on will draw more than 5w of power to run.... An iPad mini 2 ( battery is 23.8Whr) on the other hand may well be satisfied, or if needs supplementing may draw little from the battery.... At the end of the day total consumption from battery will be different for different models and based on what you are running at the time and as such the cigarette lighter charger output will determine what part the battery plays in keeping your aviation app running. Andy
Dafydd Llewellyn Posted October 22, 2014 Posted October 22, 2014 DafyddCan I suggest that you allow space within your metal encapsulation for the air to be drawn across the back of your IPAD? Logically, a charging source should reduce the heat generated within the device. Avoid the cheaper chargers. Also, avoid using a car type cigarette lighter socket. These are not reliable. That's how it's arranged - see photos . The installation is complicated by the fact that the panel you see here is shock-mounted behind a fascia in the aircraft that is structural; so the ipad tray has to be mounted on a stand-off from an existing instrument hole, such that when it's in the aircraft it stands about 6 mm proud of the fascia. As you can see, it is really a squeeze to accommodate it in the panel. In view of the upper temp limit of 35C, I may have to reverse the arrangement I intended and blow cold air onto the back of the ipad from what it shown as the outlet; and that supply may need to run through an insulated container holding a freezer brick. Glider cockpits can get very hot on the ground, so the ipad goes into the tray as the occupants climb aboard; but the cabin air temp may be too high to provide any useful cooling at low altitude. The lid of the tray is not shown in those pictures, but it opens to act as a shade hood. The 12 V charger I have is Bauhn 2.1 amp device; it seems to be the same Belkin charger, re-branded by ALDI, as Apple were recommending at the time. It's a cigarette lighter socket type, which I dislike, but I could not find anything more apposite at that time; maybe there's something better now (suggestions gratefully received). I'll be using a filter network to minimise the spikes going into it; the engine is a 582, and it's across a lead-acid battery. The ipad is a basic 16 Gb series one Ipad mini, and I use a BadElf Pro bluetooth GPS. The only application will be Ozrunways.
Bruce Tuncks Posted October 22, 2014 Posted October 22, 2014 I'm still waiting for somebody to tell me how to set a LiFePO4 on fire. How about connecting one to the mains using a bar-radiator to stop blowing the fuses and a big diode to turn the mains AC into pulsed over-charging DC? The pulsed DC will have a peak value of 339 volts at 50 cycles per second.Surely this would be worse than even a Ducati (Rotax) charger. How about hanging one over a fence at the farm and shooting at it? How about using an ignition system and delivering 20,000 volts as a "charge"? If you can't tell anyone how to set one on fire deliberately, how can you expect people to believe that this is a real risk and not an imaginary one? I do accept nomadpetes point that the deliberate overcharge I did with an uncontrolled battery charger didn't emulate the jabiru charging system exactly, but surely somebody can come up with something bad to do to these batteries to show that they have this property of catching fire, if in fact they have this property in reality. I'm still offering a modest prize for a suggestion which can stand up to being checked out. I'd really be happy to have this question answered with real evidence which can be replicated. regards, Bruce
jetjr Posted October 22, 2014 Posted October 22, 2014 Get one of the guys running Jab engines in a test cell to hook one up Oscar, Ian ??
Oscar Posted October 22, 2014 Posted October 22, 2014 Sorry, jj - can't help you here, our engine has a CAMit alternator and Ian's will also (obviously!). However, it occurs that you don't need a test cell for this; just a representative Jab. charging system set-up with an electric motor to spin it. I'll have a scrounge through my 'old parts' bin and see what's there and what can be done; since I am very keen to use a LiFePO4 battery, some testing would seem to be sensible.
Head in the clouds Posted October 22, 2014 Posted October 22, 2014 I'm still waiting for somebody to tell me how to set a LiFePO4 on fire. How about connecting one to the mains using a bar-radiator to stop blowing the fuses and a big diode to turn the mains AC into pulsed over-charging DC? The pulsed DC will have a peak value of 339 volts at 50 cycles per second.Surely this would be worse than even a Ducati (Rotax) charger.How about hanging one over a fence at the farm and shooting at it? How about using an ignition system and delivering 20,000 volts as a "charge"? If you can't tell anyone how to set one on fire deliberately, how can you expect people to believe that this is a real risk and not an imaginary one? I do accept nomadpetes point that the deliberate overcharge I did with an uncontrolled battery charger didn't emulate the jabiru charging system exactly, but surely somebody can come up with something bad to do to these batteries to show that they have this property of catching fire, if in fact they have this property in reality. I'm still offering a modest prize for a suggestion which can stand up to being checked out. I'd really be happy to have this question answered with real evidence which can be replicated. regards, Bruce I agree Bruce. In my opinion the LifePO4 batteries are very safe as far as fire is concerned. I've gone over this extensively on two other forums but there are always those who can't see the difference between Lipos and Lifes and/or who are convinced that it's the lithium that's the problem ... LifePO4s are used extensively in various forms of motorsports and by many performance motorcycle owners on the road and I've not heard of a single instance where the battery has caused a problem - of any kind. In fact every person who uses them that I've spoken to, is very enthusiastic about them and all agree that their machines start much quicker and more reliably due to stronger cranking. Lipos catch fire and support fire because the electrolyte (not the lithium) is extremely volatile and flammable and does not need an external source of oxygen to maintain combustion as it produces its own, making them very hazardous and difficult to extinguish as discussed previously. The electrolyte in Lifes is not at all flammable and will not support a flame. Additionally many quality brands of Lifes (my Shorai for example) have a milspec casing made from flame retardant carbon fire. I cannot enter your competition to set a Life on fire Bruce, as it would appear that they will not burn whatever you do to them. A Life distributor demonstrated the only way he could envisage of igniting one by putting it in a fire fully charged but it just became a bit charred so then he set to it with an oxy-acetylene flame ... it still didn't do anything nasty. Motorsports users of Lifes just replace the lead-acid battery with a Life battery and apparently don't change anything to do with the charging system. Lifes can be charged far more rapidly than lead-acid batteries, a general rule is that they can be charged at the same rate as their AH rating i.e. an 18AH can be charged at 18amps, a 30AH can be charged at 30amps etc. A Rotax 912 has a 20A charging circuit IIRC so as long as some onboard system is drawing at least 2A then an 18AH (recommended battery for the 912) should be charged without exceeding its charging rate - but even if you do exceed it you won't set the battery on fire, it'll just shorten its life a bit. The manufacturers do recommend balancing the cells occasionally to get the best performance from the battery but it is not essential. They recommend using a balancing charger every 6 months or so. For those who do not have a balancing charger (i.e. most people) some distributors offer a service of doing this for you. You just mail the battery to them and they return it the next day. There is nothing toxic or dangerous to humans, animals or plants in Lifes (read the MSDS ...) and the instructions for the disposal of them is simple, just throw them in the garbage. Lipos are a dangerous good so they may not be carried by air (or by post that goes by air). Lifes are not a dangerous good and may be carried by air and by airmail. There is a restriction on the carriage of Lifes though. Although they are not a dangerous good the very fact that they have a strong electrical charge that can be discharged very rapidly due to their low internal resistance, means that if both of their terminals came into contact with a piece of metal or other conductor then a fire could be caused by the short-circuit. The battery would not catch fire! But the metal causing the short could become red hot, white hot etc and set fire to other material in contact with it, or nearby. For this reason the combined size of Lifes that can be carried in each sealed package is restricted to 30AH IIRC. By using a Life battery my plane is 7kg lighter because my battery weighs 1kg and the lead-acid equivalent would weigh 8kg. That's a hell of a saving for me as I designed the plane around the reduced weight but it can't benefit every plane owner if the weight of the battery is needed to maintain the proper CG. I'm not recommending the Life type of battery, that wouldn't be wise in this present-day litigious world but it seems that they work exceptionally well for some folk ... .... Another problem of this battery chemistry is that unlike Lead Acid batteries where the voltage can be used as an indicator for the state of charge, LIFEPO batteries maintain their voltage almost constant and then drop dead in a flash possibly at a time when you last need it .... Not in my experience. Charged and unused the Life battery holds its full charge of 14.4V for more than 6 months, and easily 12 months if kept cold. The dissipation of the charge when in use is linear just like a lead-acid battery and can be measured predictably with a voltmeter. They should not be allowed to drop below about 12.8V and would be too low for effective cranking when they reach 12.5V in the no-load condition. I've never heard of one "dropping dead in a flash" unless it was faulty. 2 1 5
SDQDI Posted October 22, 2014 Posted October 22, 2014 I've found this an interesting thread. I currently run an odyssey battery and have had no trouble with it (except when the key was left on........ Long story) and I plan on keeping it till it's finished it's useful life but when it comes time to change I was thinking of looking into a LiFe battery. My battery is under my seat which means getting a lighter one won't dramatically affect c of g but would help with auw. BUT because my battery is under my seat I would like to be VERY sure that it wasn't going to cause me any trouble. Maybe I should design a battery ejector:cool: Might not be too good over built up areas but I'm not aloud to fly over them anyway:chuffed:
Guest Andys@coffs Posted October 22, 2014 Posted October 22, 2014 I believe the point that was being made is that Lead Acid as it discharges slightly drops its voltage so that by measuring the unloaded voltage at any point you can approximate charge remaining. Lithium based batteries, and many other battery chemistry solutions don't have significant appreciable drops. Furthermore Lead Acid voltage changes are significant as you proceed through the last 5 - 10% of charge, and are almost digital on/off with Lithium. The point being made is, as by example, if a Lead Acid battery was at 3% remaining charge it would be most unusual if the owner was not aware of it due to changes such as distorted audio, very dull LCD backlights, some electronic systems may well have already failed due low input voltage. Lithium by comparison will be likely working without issue right up to the point where it is game over everything stops...... So, in summary the Lead Acid solution gives increasing indication of imminent exhaustion, the Lithium Battery's do not. I absolutely accept that there is a significant difference between the 2 chemistry's, however my fear is that given the amount of control/marketing excess that occurs in places where such battery's may be available online (ebay being one example that comes to mind) I fear that someone will one day buy a cheap battery believing its the iron chemistry but the seller...who meanwhile fades back to complete anonymity has substituted a cheap ion substitute thinking what's the worst that can happen...of course we having read this thread know only too well the worst that can happen...... Recreational aircraft owners need to look to our bigger commercial aircraft owners/operators to pick up some of their possibly sensible behaviours......They will not buy any aircraft fitting where they cannot be sure of the providence of the parts....I don't think we need to get to the point where we need certificates of conformity, or as for rotables, a complete history of the parts and subcomponents that make up the solution, however it may well be worthwhile understanding how and where your supplier purchased his offerings, and how sure you and he are that what is being offered is genuine and not counterfeit and that the manufacturer of the part is a reliable and repeatable supplier....
eightyknots Posted October 22, 2014 Posted October 22, 2014 I've found this an interesting thread.I currently run an odyssey battery and have had no trouble with it (except when the key was left on........ Long story) and I plan on keeping it till it's finished it's useful life but when it comes time to change I was thinking of looking into a LiFe battery. My battery is under my seat which means getting a lighter one won't dramatically affect c of g but would help with auw. BUT because my battery is under my seat I would like to be VERY sure that it wasn't going to cause me any trouble. Maybe I should design a battery ejector:cool: Might not be too good over built up areas but I'm not aloud to fly over them anyway:chuffed: In summary, DON'T put a LiPo battery in your aircraft. If you do, you're definitely in the hot seat! 1
Old Koreelah Posted October 23, 2014 Posted October 23, 2014 ... Avoid the cheaper chargers. Also, avoid using a car type cigarette lighter socket. These are not reliable. How do we charge in flight without using cigarette-lighter socket chargers? They are supplied by Apple and what aircraft has a 240v outlet? I use a dual- voltage Belkin, to which I plug my iPhone and iPad via USB.
Old Koreelah Posted October 23, 2014 Posted October 23, 2014 Maybe we are being over-cautious. The iPad uses a LiPo battery, which can get warm while being recharged. Most iPads seem to be encased in leather or plastic, which must almost totally prevent heat loss thru the rear surface, which is a major cooling area for Apple notebooks. When I've mentioned this to Apple staff they point out that about 200 million iPads have been sold, and almost none have cooked.
DonRamsay Posted October 23, 2014 Posted October 23, 2014 As we said above, running an iPad (with a previously fully charged battery) on 12V power stops the battery from charging or discharging in flight and it remains cool. The charging system does have to be able to deliver 2 Amps as 1 Amp is just not enough current.
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