The real dangers of Lithium Ion batteries.......

[Guest Maj Millard]

I have shown an active interest in the dangers of fitting one of the new Lithion Ion batteries to your recreational aircraft lately.

 

The problem was highlighted by Ed Smiths article in a recent Sport Pilot magazine in response to his experience with a fatal accident caused directly by one of theses batteries in WA. Additionally we had an emergency landing in SE Qld after one ran away and filled the cockpit of a Zenith 601 with toxic white smoke. It is very fortunate that this aircraft wasn't that high and there were suitable fields below.

 

On the weekend whilst attending the AGM and RAAus board meeting at Lethbridge and Geelong I had a good opportunity to talk with Ed Smith indepth one-on- one about these batteries dangers and shortcomings.

 

Ed is a highly qualified electrical engineer and importer of the FK range of aircraft from Germany.

 

In summery his comments about the battles are as follows....

 

* They are being sold across the counter as replacement for lead/acid batteries, which they are not.

 

* They are not compatible with any charging systems utilising permanent -magnet type charging systems. (IE:

 

Rotax or Jabaru.

 

* If used with these types of charging systems the crucial time for an overheat is around 90 minutes.

 

* If the battery overheats and ignites it is virtually impossible to extinguish with normal medium such as water or foam. This is because they burn at extremely high temperature and chemically create their own oxygen which continues to support rapid re-ignition.

 

* The only safe way to extinguish after ignition is to immerse them in water, with salt water being preferred to interfere with the chemical reactions occurring when the battery is burning.

 

* The flame that is ejected from the battery vent apature has a temperature similar to that of oxy- acetelene and will cut through metal including an alloy engine case effectively as well as any cutting torch.

 

Ed and I chatted about the fatal accident in WA which he investigated. The battery stored in the tail boom had overheated and ignited unknown to the pilot, softening the fiberglass resin which caused tail boom failure and a loss of control from 1500 Ft. The pilot had already sensed control problems, and had reduced power in preparation for a descent and landing in a suitable paddock. He didn't make it.

 

A local farmer who witnessed the accident close by, drove rapidly through fences in his fire- fighting 1200Ltr tanker truck to render assistance. After expending the whole water load at the burning aircraft he stated that the fire kept erupting and he couldn't extinguish it !....Ed found during his investigation that the flame being ejected from the battery vent had contacted the nearby engine case and had melted a hole through the alloy case as if someone had used a cutting torch.

 

Without using the electrical technical terms that Ed would use as an electrical engineer, what basically happens is that when charged with a permanent - magnet type alternator, the electrical charging sine waves become much closer together over the 90 minute period with resulting higher voltage peaks, way above the batteries voltage rating.. These cause rapid overheating of the battery with a resulting fire.

 

Additionally these higher voltages can ente the aircraft's electrical system instantly damaging any sensitive avionics, radios etc.

 

Eds very strong recommendations ?." I would never fit one of these batteries to any aircraft !.."

 

 

[Nobody]

The distinction needs to be made between lithium iron phosphate (LiFePO4)

 

 

 

http://en.m.wikipedia.org/wiki/Lithium_iron_phosphate_battery

 

 

 

and lithium-ion polymer battery

 

 

 

http://en.m.wikipedia.org/wiki/Lithium-ion_polymer_battery

 

 

One type is probably ok in an aircraft. The other not so much...

 

 

 

[bexrbetter]

One type is probably ok in an aircraft. The other not so much...

Please don't tell me which one, I'll go find out for myself.

 

 

[Guest Andys@coffs]

I too heard Ed's thoughts, for the technical minded Ed told Ross and I it was because voltage regulation in permanent magnet generators is done via pulse width modulation were the average voltage is limited by varying the pulse width so that the average voltage from pulse to pulse is the required voltage. The peak voltage however is whatever the permanent magnet setup produces. The peak voltage is what overheats and pierces the dialectric layer in the battery, which is an oxidising material.

 

AGM on the other hand is heavier but cares little about the method of regulation.

 

Ed made the point that some newer battery's had a method of sensing the peak voltage and/or the internal temps and disconnecting the battery but in so doing the dangerous peaks were now presented directly to your avionics where previously the battery was absorbing the peak. Modern glass avionics were likely to cease to play the game anymore......

 

It was a case of preaching to the converted in my case, a few kgs of saved weight in a place that affects c of g to me is not worth the risk. It's true the lithium iron is supposed to be better but equally true that unless dealing with a special knowledgeable organisation how sure are you that you will end up with iron and not ion.

 

 

[Guest Maj Millard]

Thanks Andy for putting the polish on it for me....obviously there are others ( like you and ED) with far more expertise than I in the electronics field, when it comes to the nitty gritty.

 

I am very concerned about members safety when using these new products. We already have had a couple of demonstrations of what they have the potential to do in aircraft, with the only obvious advantage being the lightweight nature of them.

 

This in no way for me balances out the potential serious dangers of these products.........Maj.....

 

 

[Guest Maj Millard]

The distinction needs to be made between lithium iron phosphate (LiFePO4)  

 

http://en.m.wikipedia.org/wiki/Lithium_iron_phosphate_battery

 

 

 

and lithium-ion polymer battery

 

 

 

http://en.m.wikipedia.org/wiki/Lithium-ion_polymer_battery

 

 

One type is probably ok in an aircraft. The other not so much...

Thank you nobody for your valuable information imput here..........Maj.....

 

 

[Guest Maj Millard]

Additional to my original post in respect to extinguishing the fire in the WA fatal aircraft crash. Ed mentioned that when fire department vehicals arrived they also attempted to extinguish the fire using foam but were also unsuccessfull. The battery appeared to be the source of the constant re-ignition......

 

Also he mentioned that Harley Davidson motorcycles use permanent-magnet type alternators and that we could expect to see an increase in problems there as those owners also start fitting Lithium Ion type batteries.......................Maj......

 

 

[Bruce Tuncks]

On my setup, there are a few big capacitors between the positive and ground busses, and the charging feed comes from the positive buss.

 

Although I haven't checked with an oscilloscope, I would expect these capacitors would smooth out the peak pulses. That's what capacitors do. However as I have said on the other thread, I am switching out the charging as soon as the start-draw has been replaced and this is well before take-off.

 

Here's a safety test I tried on a spare LiFePO4. I deliberately ruined one by overcharging to see what would happen. ( 6 amps from a crude charger with no voltage cut-off, the setup placed where a fire would be safe). Well it sure puffed up and the terminal voltage was up near 20 volts but no fire or anything.

 

But I appreciate the concern people have, and that inflight fire story was awful. Maj is right to be concerned.

 

Here's a question... what would you do if you deliberately wanted to try to get a LiFePO4 to ignite? Maybe connect it to the 240 volt mains with a suitable series load so you didn't blow the household fuses?

 

What about a modest prize for the person who finds how to ignite a battery ? I'll donate a modest prize.

 

This isn't a frivolous point. We carry petrol, and there is no prize for demonstrating how to set that on fire.

 

regards, Bruce

 

 

[Guest Andys@coffs]

Bruce

 

Your approach is fair and reasonable and more importantly informed. I believe Ross and my concern is more for members that don't have your understanding or cautious approach.

 

With regard your question the fatal that Ed spoke to us about was a result of fire in the battery, the engine block had a clear melt hole in it from the close by battery location, the hole size was very significant and in a place where there was no alternate source of possible cutting temperature flame to open the block as occurred. I accept that doesn't answer your question as to exactly how, nor do I known what chemistry the fitted battery was, Ed probably does and would likely welcome the chance to have the discussion with you.

 

Andy

 

 

[Geoff13]

But if the battery was stored in the tail boom as stated earlier, how did it burn a hole in the engine block?

 

 

[Guest Andys@coffs]

It was a pusher

 

 

[eightyknots]

* If the battery overheats and ignites it is virtually impossible to extinguish with normal medium such as water or foam. This is because they burn at extremely high temperature and chemically create their own oxygen which continues to support rapid re-ignition.

* The only safe way to extinguish after ignition is to immerse them in water, with salt water being preferred to interfere with the chemical reactions occurring when the battery is burning.

 

* The flame that is ejected from the battery vent apature has a temperature similar to that of oxy- acetelene and will cut through metal including an alloy engine case effectively as well as any cutting torch.

:yikes:Yikes! I hope that they find a way to improve these lithium ion batteries to the point where a lighter battery such as this will be a safe proposition in light aircraft.

 

 

[Nobody]

:yikes:Yikes! I hope that they find a way to improve these lithium ion batteries to the point where a lighter battery such as this will be a safe proposition in light aircraft.

Or use a lithium iron phosphate (LiFePO4) battery?...

 

 

[Keith Page]

Thank you Maj.. Job well done.

 

Now it is a simple execise for all "" Forget about those Lithion Ion batteries completely ----- DO NOT ----- use them""

 

Now put ones research energy into something other than batteries and share that.

 

Thank you Maj.

 

Regards

 

KP..

 

PS..... Which batteries are used in the electric planes?

 

Yes ------ I know they are charged before one takes off, however plane could burn before ya take off.

 

 

[eightyknots]

Or use a lithium iron phosphate (LiFePO4) battery?...

I hope that those LiFePo4 batteries do not prove to be life-threatening (after a few years of real aviation use) either.

 

 

[Guest Maj Millard]

On my setup, there are a few big capacitors between the positive and ground busses, and the charging feed comes from the positive buss.Although I haven't checked with an oscilloscope, I would expect these capacitors would smooth out the peak pulses. That's what capacitors do. However as I have said on the other thread, I am switching out the charging as soon as the start-draw has been replaced and this is well before take-off.

Here's a safety test I tried on a spare LiFePO4. I deliberately ruined one by overcharging to see what would happen. ( 6 amps from a crude charger with no voltage cut-off, the setup placed where a fire would be safe). Well it sure puffed up and the terminal voltage was up near 20 volts but no fire or anything.

 

But I appreciate the concern people have, and that inflight fire story was awful. Maj is right to be concerned.

 

Here's a question... what would you do if you deliberately wanted to try to get a LiFePO4 to ignite? Maybe connect it to the 240 volt mains with a suitable series load so you didn't blow the household fuses?

 

What about a modest prize for the person who finds how to ignite a battery ? I'll donate a modest prize.

 

This isn't a frivolous point. We carry petrol, and there is no prize for demonstrating how to set that on fire.

 

regards, Bruce

Bruce , It doesn't really need to catch fire to ruin your day as was demonstrated by the two in the Zenith 601 in SE Qld. A cockpit full of choking acrid white toxic smoke will sure get you thinking you made the wrong decision in fitting one.

 

 

[Guest Maj Millard]

Thank you Maj.. Job well done.Now it is a simple execise for all "" Forget about those Lithion Ion batteries completely ----- DO NOT ----- use them""

Now put ones research energy into something other than batteries and share that.

 

Thank you Maj.

 

Regards

 

KP..

 

PS..... Which batteries are used in the electric planes?

 

Yes ------ I know they are charged before one takes off, however plane could burn before ya take off.

Good question Keith...

 

 

[Dafydd Llewellyn]

So where do we stand with an Ipad mini (Li polymer battery)? Obviously one should not charge it in flight; and it needs to be kept out of direct sunlight; but if one does those things, what's the risk?

 

 

[flying dog]

Bruce,

 

I read your post:

 

Although I haven't checked with an oscilloscope, I would expect these capacitors would smooth out the peak pulses. That's what capacitors do.

 

Errrr.... No. That isn't what they do. Well, not the SMOOTH OUT PEAKS part.

 

If there are spikes, they will not reduce them.

 

Capacitors WILL smooth drops in the voltage, but can't reduce spikes.

 

COILS can do that, but it gets difficult to do it because a lot of maths comes into it.

 

 

[nomadpete]

My understanding is that Bruce didn't actually simulate the Rotax or Jab charging regime..

 

The brute force "regulator" used here allows unregulated charge CURRENT to be absorbed by the battery until the SCR's in the regulator decides to cut off the pulses. It isn't a proper pulse width regulator in the true sense of the words. I suspect that the superior low internal resistance of these new Lithium batteries would take in more charge current than the good old Lead Acid types. This would account for a mere 6 amps not setting fire to the battery in spite of the battery failing in other manner.

 

Note that the ROTAX charging system is a Ducati motorcycle system (is branded so.) Since most motorcycles have the identical regulator design, there will likely be more than one motorcyclist walking home (to buy a new bike) after fitting a lithium battery.

 

In any event, these new batteries are a serious hazard.

 

 

[nomadpete]

PS

 

Further to my post, your Ipad, mobile phone etc is unfortunately vulnerable to battery failure (websearch it for details).

 

Fortunately, however, these devices have the advantage that they are much easier to jettison than the system battery in your aircraft.

 

 

[Dafydd Llewellyn]

Bruce,I read your post:

 

Although I haven't checked with an oscilloscope, I would expect these capacitors would smooth out the peak pulses. That's what capacitors do.

 

Errrr.... No. That isn't what they do. Well, not the SMOOTH OUT PEAKS part.

 

If there are spikes, they will not reduce them.

 

Capacitors WILL smooth drops in the voltage, but can't reduce spikes.

 

COILS can do that, but it gets difficult to do it because a lot of maths comes into it.

I had a problem - or at least a potential problem - with using the Jabiru ignition switch leads as a source of RPM data for an MGL Infinity E-3 instrument; the E-3 manual tells one to use 10 K ohm resistors in the leads, but the oscilloscope still showed spikes (well over 50 volt) at the far end, which I decided I could do without. A small ferrite-ring core with about 50 turns of wire, short-circuited, simply thread the RPM sense lead through it, and the spikes were reduced by about a factor of ten. No maths, just grab an existing small ferrite ring choke, short circuit the ends of the windings, and it works. No doubt one could be more scientific, but . . .

 

 

[Dafydd Llewellyn]

PSFurther to my post, your Ipad, mobile phone etc is unfortunately vulnerable to battery failure (websearch it for details).

Fortunately, however, these devices have the advantage that they are much easier to jettison than the system battery in your aircraft.

Ta - That's what I understood. I've installed my Ipad mini in a stainless-steel tray, mounted on the instrument panel, with a stainless-steel cover that opens to act as a shade hood, or closes to contain fumes etc. The tray has an air-extraction tube (1/2 inch bore) that draws cabin air past the back of the Ipad & dumps it overboard, to cool the thing and remove fumes. Hopefully, that will serve in the event the Ipad gets hot & bothered, but I've no way to assess its adequacy.

 

 

[nomadpete]

Ta - That's what I understood. I've installed my Ipad mini in a stainless-steel tray, mounted on the instrument panel, with a stainless-steel cover that opens to act as a shade hood, or closes to contain fumes etc. The tray has an air-extraction tube (1/2 inch bore) that draws cabin air past the back of the Ipad & dumps it overboard, to cool the thing and remove fumes. Hopefully, that will serve in the event the Ipad gets hot & bothered, but I've no way to assess its adequacy.

Fortunately the mobile device folk are quite cautious about the negative sales implications of their devices setting fire to the proud new owner's handbag (or whatever) so they have put a lot of thought into controlling the battery charging within the device. There is still the remote possibility of a problem. Therefore:

 

Risk assessment 1 0 1 :

 

Probability of the hazard - LOW

 

Consequences of hazard - Fatal

 

Control of risk available to operator - LOW

 

Actual risk is assessed as HIGH

 

I don't even have one in my bike. (and I would at least be able to walk away from the fire if it eventuated)

 

 

[DonRamsay]

So where do we stand with an Ipad mini (Li polymer battery)? Obviously one should not charge it in flight; and it needs to be kept out of direct sunlight; but if one does those things, what's the risk?

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