Dafydd Llewellyn

For voltage and current, think of it this way. The source supplies the voltage and the load draws the current. As long as the supply can supply as much current as the load needs, then everything is fine. You could have a supply that is capable of supplying 1000A and it would be quite safe to connect to your iPad, because it is the load (ie the iPad) that controls the amount of current drawn. On the other hand, if the supply can't supply enough current to keep the load happy, then the voltage will droop and all bets are off. So, if your genuine Apple wall charger that came with it is rated at 1A, then it means that the mini iPad must require less than that amount, and any cigarette lighter charger that can supply that much or more is fine (all other previously discussed issues being already accounted for, of course).

That's certainly the case where Ohm's law controls the charging current and there are no other constraints; this is usually the case with a lead-acid battery in a car. In that case, as you say, only the charger voltage matters - provided the charger voltage cannot exceed the fully-charged battery voltage, it can never supply more current that the back emf and the internal resistance of the battery allows. However, it is possible to damage a lead-acid battery that is close to fully discharged if the charger has more current capability than the battery can handle without physical damage - and Ni Cad aircraft batteries had to have the charge current regulated by the battery temperature. So it ain't necessarily that simple, I suspect.

 

What I do NOT know is (a) Whether there are constraints of that nature for the Ipad mini; (b) Whether there is protective charge control circuitry built into the Ipad to cover this - or whether it is controlled by limiting the output of the charger. An LT3083 can produce 3 amps. That's three times what the Apple-supplied wall charger can provide.

 

Further, I don't know whether the 1 amp Apple charger can keep up with the device if it's on full brightness continually, as it's likely to be in the aircraft. So it's not a given that 1 amp is sufficient. I suppose it's a case of suck it and see.

 

 

Ah, Dafydd, CAO 108.56 was cancelled 9 July 2013.

Yes, the CAO s are being slowly phased out. What has it been replaced by, do you know?

 

 

DafyddTheir point is valid imho. Within RAAus Aircraft I would guess that 75% or more use the Cheap non TSO'd altimeters. No LAME instrument fitter is going to issue a serviceability tag for these generally Chinese sourced instruments because there is no manual that defines the checks, the tolerances and the approved repair methods that are to be used if they need to be calibrated, nor at what point calibration via adjustment is actually needed. (Is the instrument out, or just sh!tty?....or more like reality its Sh!tty and out)

 

As such what determines whether a particular instrument is serviceable?

 

Andy

If it meets the error limits given in CAO 108.56, it's servicable, I think you'll find. If you have one of the Cheep altimeters, you may learn that it was never within a Bull's roar - but that's the reason for the calibration requirement. Check CAO108.56 against the RAA TM excerpt above - I think you will find the TM is a verbatim quote of CAO 108.56 (as, really, it must be, if we are to maintain the same separation standards as the rest of the airspace users).

 

 

Dafydd are you sure about 2.1A.....I just checked my Ipad 3 charger and its rated at 5.2V and 2.4A giving approx. the rated 12W.I have used this one to charge the wifes iphone5 which only needs a 10W charger and it works fine, just a bit faster....

 

Andy

No, Andy, I'm not sure - that's why I asked. The wall charger that came with my ipad mini is Apple A1402, which appears to be 1 amp rated. There are backup batteries for them, which would suggest that the ipad itself may have some form of charge - current limiting. I simply do not know whether it's safe to plug the thing into a 5V source of arbitrary current capability.

 

 

What I don't yet know is whether it is necessary to limit the output current for the ipad supply to 2.1 amps.

 

 

I think I have a workable answer: You use one of these http://www.powerstream.com/dc-dcz0603.htm to drop the 12 volt nominal to 6V precision; and you then use a linear regulator based on an LT 3083 to drop it to 5V with nil output ripple.

 

This runs straight off the 12V battery and reduces the heat loss to a minimum (about 3 watts) and has nil output ripple. Don't need to split the 12 V battery into two 6V halves.

 

 

Dafyydd, please don't take what I said as implying that linear is the better way to go. Good switchmode supplies are the bee's knees. They'll cope with the small repetitive spikes that the Sport Pilot article was talking about (as long as they are not designed to be borderline at 14V like a real cheapie might be), and they are no more susceptible to to the kV spikes of startup and shutdown than a linear reg.The biggest problem with running a linear reg off a 6V battery is that linear regs require a certain level of step-down, and even the best ones will be borderline at 6V. As soon as the battery voltage starts to droop, so will the output and the iPad will start getting very iffy. Switchmode reg, on the other hand, will keep supplying as the input voltage droops (for a while at least).

Yes, thanks for that; I'm looking at low-dropout regulators at the moment. The ones I've found so far won't handle more than 6.5 V input. Bear in mind that whilst the engine is running, the battery voltage is going to be around 7 volts, not 6 volts. A 7 AH Yuasa in good condition will take about one hour at 2 amps load to droop to 6 volts from a full charge; in a motor-glider application, one is likely to have to run the motor every so often; in still air, about every 20 minutes; in more favourable conditions, maybe every hour; you have to watch the battery voltage to make sure you have enough battery to re-start the engine reliably. The ipad does not need to be on charge 100% of the time; mainly, I think, you want it to be at full charge when you turn the motor off after takeff and climb to where the lift is (usually, fairly close to cloudbase); that's probably going to be about 15 minutes of engine run time, plus whatever additional time the 6V battery can stay above the dropout voltage - so if the system gets the ipad to full charge within about 3/4 hour of takeoff, and tops it up periodically throughout the flight, it should not be necessary to recharge every night. That's essentially the aim.

 

If there's an issue with the ipad battery from the inherent noise from a switch-mode supply - and that's an unknown at this stage; lacking data on the maximum noise level it can tolerate, one cannot evaluate that - it seems advisable to at least research low-dropout linear regulators. It may well be that I can use a high-quality TI or similar switch mode regulator, and if so I can dispense with the 6V battery setup. I'm still in research mode; however I would not have known where to start, without the thread.

 

 

so technically every one is grounded again? except 95:10who does these instrument checks and sign offs?

and add another incidental cost to affordable aviation.

No, of course not. Just use a manometer (you can make it yourself) to calibrate the ASI and also to check the plumbing for leakage; and send your altimeter to an instrument shop at the required intervals. Forget the position error, it's a given in any certificated aircraft. The instruments do not need to be TSOed; they need to be within the limits of CAO 108.56 when you check them, that's all. There's nothing new about any of this.

 

 

Dafydd,If you intend to go with a linear voltage regulator, please get some advice on cooling. The heatsink required to cool your 18watts (in still air) is quite large. Whilst the linear regulator is a great way to smooth the pulses out (as long as pre-filtering prevents any spikes exceeding the regulator's max input spec), you will find that the same pulse suppression can be achieved with a normal good quality switched mode design. Also, the switch mode unit is available 'off the shelf' with all that suppression built in. Well, at least that is true if you buy a quality unit.

I have not yet seen data on the Jabiru or Rotax regulators.

 

However, the Rotax 912 coils that I replaced were a three phase type branded Ducati.

 

"Normal" motorcycle regulators ( and I expect that Ducati would design their coils to suit this) rely on a 'short circuit' type regulator. These work by triggering a SCR to short each coil when the terminal voltage reaches 14 volts. It does this each cycle of the output voltage. So you get pulses of 14 volts going to the battery and the battery 'holds over' until the next pulse of 14 volts. Any excess power is dissipated in the coils themselves. I have put a oscilloscope across it and there are spikes of about 20 volts superimposed on the switching instants. You will find that any good automotive plugin device should not be bothered by this. I am aware that other small engines use single phase of the same concept, and similar regulators. Note that this is not a true switch mode regulator. Maybe it could be called a shunt regulator. If a true switch (series) mode regulator was employed, the potential generator coil voltage could spike much higher when the regulator pulses off. I would expect that the coils would have to be designed with better insulation to withstand this. Also there would have to be a spike suppression of some sort, but that is just an assumption.

 

Pete

 

PS don't use cigarette lighter sockets

Thanks, Pete; however the cooling issue will be nine times less if I'm converting six volts to five volts, rather than twelve volts to five volts. And yes, I'm familiar with the use of heat sinks; I used to be in charge of the CSIRO F-27, in which we had three 24V DC to 240V AC solid-state inverters, about 5 KVA each, to cater for the scientists who insisted on designing their flight gear to run on 240 V. This also showed me how lousy the waveform can be from such equipment, and what problems can arise from that. We used to call one of the scientists "Captain Kilowatt". I'm also familiar with the use of BIG SCRs to drive vibratory feeders that feed iron ore into blast furnaces or rocks into gravel crushers.

 

The form of voltage regulation you describe is used by Jabiru, I believe, but I think its ripple problem is mild compared to the single-phase setup on the Rotax 582, despite the high RPM of the latter. I'd assume they switch the coil to ground, rather than to open circuit; they can't be that stupid. I consider cigarette lighter sockets suitable to use for throwing at stray dogs, etc.

 

 

There's always 2 sides to every story.....Try and make that claim if you fly in an open cockpit.......I have lost maps overboard, followed by an instantaneous Brrrrp as the prop dealt with the offending map when trying to refold to cover the ground im currently over..... I'd need to be going a whole lot faster to have the cockpit wind grab hold of the ipad ....and in any event don't need to take out of the kneeboard cover or pick it up because it constantly always reflects the ground Im over..... but if it did go through the prop then navigation beyond my immediate area at that point of time is likely to suddenly become a whole lot less important:lost:

 

Andy

I've 50 years' experience in using paper maps, thanks; I converted the glovebox of my PA28, in the '80s, into a set of pidgeonhole slots to cope with them. WACs, VECs, VTCs, ERSA, the radio frequency chart, etc, etc. I used to spend hours re-folding them so they'd be right way out when I wanted them. A nightmare when you need to traverse a piece of controlled airspace and you need a different part of the chart in a hurry, because ATC wants an ETA RIGHT NOW. They are even worse to use in the confined cockpit of a glider; the compensating factor used to be that gliders cover the ground fairly slowly. But when you put a motor on one, it can manage 90 kts TAS. So it's either fit an autopilot to keep it right way up whilst one wrestles with maps, and where the H has the timescale got to? Or mount the mini ipad on the panel (there's just barely room to do so, and nowhere else to put it). In a glider, one is frequently looking at the map through a final glide computer, which is a further chore OzRunways can help with, with its glide range display. On the whole, I'd rather be watching for other traffic, and generally keeping my head out of the cockpit. Situational awareness is what it's all about, and the moving map is a vast improvement over paper - and you can leave the map display alone and ERSA becomes the sole piece of paper you need to look at. The more demanding the circumstances, the greater the advantage. Even better when it can display the traffic in one's immediate vicinity, plus the BOM weather radar display.

 

So I regard the GPS moving map (at OzRunways level of presentation) as just about the greatest improvement in aviation since Curtis invented the Aileron. I don't want it to get hung up on some lousy technical detail like a cigarette socket power adapter (what a piece of garbage to have to have in an aircraft!) ; I want to know what the alternative might be. Right now, there's no practical alternative to a mini ipad, because it's the only one that CASA accepts, at least for the flying I want to do, and it's the only one that fits in my cockpit.

 

So I make no apology for trying to discover a way to get around the problem, if indeed it proves to be one, so there will be an answer if it's needed. Others are under no compulsion to do anything whatever about it, if they don't feel like doing so. But thanks to this thread, I can see a way, and it will do them no harm if I give it a try. People are free to say "If God had meant us to fly, He'd NEVER have given us the railways", if that's what they feel, after all.

 

 

I'd like to thank everybody who has made a useful contribution to this thread; especially Andy and SfGnome; we've gone around in circles a bit, but I think we've unearthed a potential problem for panel-mounted ipads etc; and I for one, now see a potential solution. It remains to get an oscilloscope on the job and find out whether - or to what extent - the issue is a real problem. I suspect it will be, for Rotax 582 users.

 

 

Well, there you have it . . . .

 

One small point could perhaps be (I'm speculating here) that many of the cigarette-lighter style adapters offer two USB outlets - which may be a way of exporting the "wasted" power and thus reducing the heat, provided a load is connected to each of the outlets; added to the liklihood that there's a thermal shutoff built into the things - which would mean that they will likely to be charging less than half the time. My reading of all this is that if your cig. lighter adapter is charging full-time and staying nice and cool, it's likely to be a switch-mode device, and therefore likely to be putting voltage spikes into your ipad. If it's getting hot & bothered & only charging part-time, especially if it's only driving one outlet, it's a "linear" type, and probably not putting voltage spikes into your ipad. The 2.1 amp ones for the ipad will be far more obvious under this crude test than the 1 amp variety for a GPS or whatever.

 

As Malcolm Frazer said, "Life was not meant to be easy". Why not use a pair of 6 volt batteries in series, and run an LM317K linear regulator from each of the 6 volt halves, for the ipad & GPS? That gets the waste heat way down - to about 3 watts, instead of 27 for the two outlets. I'm planning to build my own L-C filter for the 12V supply to the radio & transponder, including crowbar protection; ferrite toroids are remarkably cheap, and I have some 25 MFD 450 volt polyethylene film capacitors laying about . . .

 

 

take the car for gods sake

I often do; but when I want to fly, it really does not serve. This thread has provided quite a bit of information for me, thanks to Andy (plus a bit of research). I suspect he's perfectly correct insofar as the "large" Jabiru alternator on the 3300 engine is concerned; and I now understand what he means by a "linear" adapter; it will likely give adequate performance on that alternator. It will be dissipating about 18 watts of heat in the process. I'm using a Rotax 582 on my motorized Blanik, can't fit a jab 3300, so my question is apposite. There are lots of Trikes etc flying with that motor. It will have an order of magnitude greater ripple in its power output, unless I miss my guess, so what works for a Jab 3300 may not work for it. It may indeed need a filter of some sort.

 

 

the manometer is the best way to calibrate, or at least, check instruments but there is no harm in doing a speed reference check in flight with the GPS

The manometer only calibrates the instrument. There are far more errors that come from the installation, mostly from the static source. What we really need is the real airspeed, not just the indicated. To get this is easy these days. Just pick a calm morning and do a four-way GPS run. No way a single run or even a back-track run is adequate, must do the 4-way. Hold a constant indicated airspeed, and fly N-W-S-E legs, each long enough to see both indicated and ground speed stabilized. Sum the four GPS readings and divide by four. If there's more than 10 kts difference between any legs then there's a wind up there. The averaging should compensate for this bias, and it does pretty well, but the less wind the better.

 

JG

 

Y'know, this reminds me of the dog that chases cars: he hasn't thought it through - what would he do with a car if he caught one? Neither have you.

 

So, you go out there and fly a GPS course, and average this & that and come up with a total airspeed error - for one particular speed. That error comprises the total of the instrument error plus the position error plus the true airspeed correction for density altitude. So you need a calibrated ASI, a calibrated altimeter, and a calibrated OAT (we'll ignore the humidity correction and the Mach No. correction). Let's assume you had those calibrated instruments, so you could make the various corrections and calculations, and thus come up with the position error at that indicated airspeed.

 

It will almost certainly be slightly different to what it says in the Flight manual. What are you going to do about this? Amend the Position Error data in the flight manual? Guess again, pal, that's illegal unless you're an appropriately authorised person. In any case, every airspeed in the flight manual is given as IAS, assuming the FM position error and zero instrument error - so you'd have to amend every airspeed that is quoted in the FM.

 

 

the manometer is the best way to calibrate, or at least, check instruments but there is no harm in doing a speed reference check in flight with the GPS

The manometer only calibrates the instrument. There are far more errors that come from the installation, mostly from the static source. What we really need is the real airspeed, not just the indicated. To get this is easy these days. Just pick a calm morning and do a four-way GPS run. No way a single run or even a back-track run is adequate, must do the 4-way. Hold a constant indicated airspeed, and fly N-W-S-E legs, each long enough to see both indicated and ground speed stabilized. Sum the four GPS readings and divide by four. If there's more than 10 kts difference between any legs then there's a wind up there. The averaging should compensate for this bias, and it does pretty well, but the less wind the better.

 

JG

 

Does your aircraft have a Flight Manual (Pilot's Operating Handbook)? If so, look in the "performance" section - you should find the airspeed system error ("Position error") data there. If it is there in the FM/POH, why do you need to determine it again? It's an inherent result of the location of the pitot and static sources on the aircraft, and thus, not subject to change, unless you change the shape of the aircraft in an area that affects those sources. The instruments themselves, however, are subject to change over time - so checking them is a periodic requirement. You do NOT need to fly the aircraft to do this.

 

 

to put those risks in perspective, there are currently over 150M ipads running at any one time, that 3.6B hours of operation every 24 hours or 1314B hours of operation every year. Plan for the worst and manage your risks appropiately

How many of them are running on power from the lighting coil of Rotax 582?

 

 

That's a common misconception held by people who normally fly aircraft that have a healthy stick-free stability (stick force versus speed gradient - i.e. you have to push harder to fly faster, and pull harder to fly slower, than the trimmed speed). The stick force versus speed gradient for, say, a Lancair 320, is virtually nil; and it's also pretty small for most aircraft in landing mode - normal symptom is that they will not hold a trimmed airspeed in the landing configuration - and it can become negative (unstable) in a baulked-landing situation. In any of those situations, the ASI is vital.

 

Yes, one can get an aircraft with a U/S ASI (most common cause - mud wasps) and most of us have had this experience - around a circuit and back on the ground by attitude & power - but it's vastly easier to do if it has normal stick-free stability characteristics.

 

I would go further, to say that it's a common misconception held by pilots that because all the aeroplanes they have experienced fly pretty much the same, that's an inherent property of anything with wings. The reason all certificated aeroplanes fly pretty much the same (if you ignore the effects of sheer mass) is that somebody sweated blood to make certain they did. It's far from inherent, and some homebuilts that have never passed a certification process, are very different to this.

 

 

DavidTo avoid boring those not interested in electronics I wont go into huge detail, other than point you here http://en.wikipedia.org/wiki/Linear_regulator this gives a better explanation than I could put together. the thing to remember is that it uses the example of a resistive voltage divider but uses the work "like" and infers that the device is in real time adjusting the resistance values so that supply voltage (including noise and spike) are always divided down to exactly the output voltage we need, and without the negatives like having to design for a known current draw and dealing with the wasted current lost in the divider network..

 

If you need more than 1A output then instead of the TO220 style 7805 there are larger packages available in TO3 package that can supply 3A or even more if you use a large power transistor in series. If you look at the Fairchild datasheets (first provided in google with a search for "LM7805 datasheet pdf") then at the back are a number of example circuits that can be used to vary the output voltage from the stock 5V or as you need, increase the current that the regulator can supply.

 

National Semiconductors was, from memory, the developer of these regulators and the associated family, there will without doubt be a regulator that will meet your need in the family. A higher current one that comes to mind without look is the LM317K but in that case its a variable regulator and judicious use of resistors determines the final output voltage. I seem to recall that its a 3A regulator or a LM117K which is 5A out (Both need external heatsinks and not insignificant at that. In fact at higher currents its then that switchmodes start to make sense. Linear regulators in laymans terms produce heat because the spare 7 to 8V is an unwanted side effect, a switchmode supply is constantly switching between full input voltage and zero volts (and hence there is no wasted 7 to 8 v that produces heat) and uses an inductor and a series of capacitors to produce an average voltage. obviously if the pulse width of the full output becomes narrower and narrower the average voltage drops but its getting rid of the pulses that relates to the effectiveness of reducing noise at the output.

 

Andy

Thanks, Andy.

 

 

Thanks, Andy. One hears occasional complaints about intercom noise from Jabiru owners, which suggests to me that the built-in supply supression in intercoms etc is occasionally marginal for the six-pole permament magnet alternator on the jab. Most of those things would, I expect, be designed to deal with whatever comes out of a typical field-current regulated automotive-type alternator - but the voltage regulators on those can produce quite a bit of noise, too.

 

I certainly don't fancy a cigarette lighter socket in the aeroplane, no matter what's plugged into it. A hard-wired converter is definitely the way to go. By the term "linear" converter, do you mean a resistive voltage-divider type? I do not have the alternator capacity for such a luxury. I've seen this term applied to transformer style converters, which, for a DC input, must have a switch-mode device upstream, but presumably rely on some silicon iron to round-off the corners of the waveform, before feeding it into a full-wave rectifier.

 

I'm looking at the Rotax 582 lighting-coil output, which I would expect to be an order of magnitude worse in regard to ripple than the Jab alternator, and also bad in regard to voltage spikes from the regulator. So I was thinking more along the lines of trying to provide a 12 volt avionics bus with about 6 amp average capability, with the filtering / suppression at the take-off point of that bus. I'm not too keen on electrolytic capacitors for this; I've had electrolytics explode before. However power-factor correction capacitors for fluorescent lights are typically around 3 microfarad, 600 volt - and they are quite light; eight of them, giving 24 microfarad, would not be impractical - I can accommodate the bulk, and they would be easy to keep cool. So would a suitable choke using ferrite rings, presumably one would use a pair of them, one for each side of the circuit (I'm planning a 2-wire system, not a ground-return system). So you can see that miniaturization is not important to me, but reliability is. One of the compensations of an aircraft, is that cooling air is readily available. That sort of setup should go some way towards calming the 12V supply down to manageable proportions for the power supply filtering built into the avionics.

 

I will be running the ipad, a GPS, a VHF COM and a transponder off that bus. Whatever 5 V converter I use for the ipad, would draw from that bus; perhaps I should be looking at two LM 7805s in parallel.

 

 

110v-240v wall chargers are generally switchmode supplys and they can generate significant RF noise if the developer is frugal with design and or implementation of filtering circuitry. Agree that in poor design they can be lethal if you end up on the end of what you think is 5VDC but ends up being 240V ACHowever for car or aeroplane use the 12v to 5v charger we use is very unlikely to be switchmode and more likely to be a linear regulator such as the LM7805 which supply's 5v DC at up to 1.5A. So wont talk anymore about switchmodes they aren't going to be in the consumer cigarette plug pack.

 

Whether the cigarette plug is a $2 ebay special or a $50 apple one the same LM7805 will be present (they cost only cents in bulk) and whether cheap or expensive aren't likely to vary significantly in the quality of the 5V supply.

 

People need to understand that the actual LiPO charging circuitry is actually inside your consumer device, not in the cigarette charger.

 

Why use LiPO....its cause the energy density is the highest commercially available and density translates to how long between charges. Why do they thermally runaway, cause its part and parcel of the LiPO chemistry/build and lesser density puts you commercially behind your competitors.

 

No sane human will use LiPO as a replacement for an AGM lead acid battery, rather LiFEO4 is used. Thermally better but not best.

 

Andy

OK, I'm looking at a Belkin micro adapter, which is so small there's barely room for the electrons. So I have no idea whether it's a transformer ("linear") type or a switch-mode type, I can't see how there's room for either. But if what you're saying is, it's unlikely that form of DC / DC step-down converter can produce much in the way of voltage spikes, the next question is, if it has a dirty input supply (as from the switch-mode voltage regulator of a permanent-magnet battery charge regulator), how effective is it likely to be in preventing voltage spikes from passing through it? And if it is effective, what happens to the resulting heat? The thing is so small there's hardly any heat dissipation capability there.

 

 

When the Boeing Dreamliner is grounded for battery problems, what hope have WE got? Battery problems are not unknown in larger aircraft . Their condition(temp etc ) has to be monitored and you usually have access to the E&E compartment to get at them.. Using cigar lighter sockets and ODD alternators.( basically flywheel magneto's but low tension) with fairly ordinary diodes may not be up to the job. A lead acid battery holds voltage to a limit better than most other batteries, but still varies. Nev

Yep; I'll be using an Odyssey. That will handle the noisy alternator output, and I assume smooth it out, somewhat. However, it seems to me to possibly be a good idea to add some suppression on the avionics bus; it costs peanuts to obtain a ferrite ring & wrap the power lead through it a dozen or more times; and a power-factor correction capacitor for a 40 watt fluorescent lamp is neither heavy nor expensive. However, this is not my area of expertise. Obviously, it's important to supply cooling air to an Ipad or whatever, too. I suspect this issue is simply one of suitable installation design, and probably quite straightforward to deal with - but I'd like somebody with some expertise in this area to make some critical comments.

 

 

OK. take a look at this:

 

http://www.righto.com/2012/10/a-dozen-usb-chargers-in-lab-apple-is.html

 

 

I suspect its all a mute point in the longrun. Today you have a choice of paper maps or EFB, give it a year or two and I suspect you can have map data in any electronic format you like as long as it isn't paper......The reality of the battery issue is that the IPAD has as LiPO Battery and LiPO batteries do this from time to time. If we were all realistic about reducing risks then any smartphone, or indeed any mobile phone manufactured in the last 5+ years then we'd leave that behind as well cause its the same chemistry in the battery and same likelihood of occurrence just a smaller pack and therefore smaller issue if it goes into thermal runaway.

 

That said no matter how big the LiPO battery any thermal runaway is going to create some excitement!!

 

If we are on the lookout for LiPO then get rid of your GPS's cause most of them will be LiPO as well.

 

Next time I go up I might try slowing to 70kts and see if I can crack the door enough to dump a runaway device....might need it one day.....just like I might need to know how to manage my Lotto $m as well......

 

"I the flying pilot bestow this runaway thermal device on the tinder dry forest below....How magnanimous of me

 

Andy

My question is, WHY do LiPo batteries do this from time to time? Is it because we're being supplied by junk chargers that lack suitable suppression of the "spikes"? This is NOT rocket science; I suspect it's marketting of junk accessories for which there is no suitable standard. Could somebody with an oscilloscope please look at the output waveform of a few typical Ipad chargers? And would the rest of you please shut up until we get this answer?

 

 

Regardless of the above gems of philosophy, to what extent is this likely to be related to the issue of using lithium batteries in aircraft that have permanent-magnet alternators (Jabiru, Rotax) which require the battery charge to be controlled by pulse width controllers - as per the article in the latest Sport Pilot?

 

This form of battery voltage regulation essentially controls the battery charge state by chopping the alternator output into short pulses - but it does not control the maximum voltage of the pulses, and so can cause problems with lithium batteries. This looks to me to be very similar to the mode of operation of "switch mode" UPS chargers for things like Ipads.

 

It seems that RF interference is a common problem when using "cigarette lighter" chargers to run an Ipad in a car; and it seems to me to be entirely possible that the operation of a "switch mode" UPS charger may well be the source of considerable RF noise. If so, then it seems entirely possible that this form of charger is in fact unsuitable for use with a lithium-battery device, in or out of an aircraft.

 

I would like to be able to use lithium-battery devices such as Ipad and BadElf GPS in my aircraft, on ship's power. Having to re-charge them every night is not really practical for a cross-country flight that takes several days. So I'd like to know, firstly, what is the liklihood that the aircraft charging system voltage spikes can affect the output of the USB charger; and secondly, what is the liklihood that the USB charger itself is putting out voltage spikes that can lead to battery thermal runaway?

 

C'mon you fellows, there's an issue here. What's the answer? Should we be buying Ferrite rings and winding the USB charger leads through them, or what?

 

 

Dafydd, surely mounting or trailing any such things would be in breach of whatever regulations apply to modification of an LSA ?

Well done that man! Yes indeed it's a modification; this is why it's totally inappropriate to talk about this in the context of the two-yearly instrument calibrations; it's not for calibrating the instruments - it's for calibrating the pitot-static system. However in certification testing, when this IS appropriate, one is always working on an experimental certificate under CASR 21.191(a) or 191(b).

 

CASA's AC: EAA members may read their excellent articles on this subject wrt homebuilt aircraft. The method is also acceptable for FAR 23 production aircraft - refer the FAR 23 Flight Test Guide. Sure it has some limitations but .... off topic.

I agree, it's an acceptable method - just not one I would choose to use. However, it can't be used for speeds for which it is necessary to dive the aircraft - so it won't cover the full speed range of most aircraft. But these methods are NOT for the two-yearly instrument calibrations, for which they are entirely inappropriate.