Why we still use heavy lead-acid batteries in GA planes

NoHeat

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Mike Busch said it's because lithium batteries can easily catch on fire, and now I believe it -- here's the All-Nippon-Airways Boeing 787 APU battery that caught on fire recently:

1-7-12_JAL787_APU_Battery_s.jpg


Click here for a very big photo.
 
Thermal runaway is a known problem with lithium batteries. No surprise there. Surprising there isn't something to prevent/counter it thou


-VanDy
 
Lithium batteries, when used properly can be very reliable. All smartphones, laptops, and RC aircraft use them (though the latter have no protection circuitry for them at all and hence more failures occur here).

However, if you don't absolutely need the power density, the risk is unnecessary. The power demand on your GA aircraft is probably 1/1000 of a 787 (not counting electric heat), so it's somewhat of a different context.
 
rcpilot said:
All smartphones, laptops, and RC aircraft use them (though the latter have no protection circuitry for them at all and hence more failures occur here).
Click to expand...

Wasn't there a problem not too long ago with iPhones catching on fire? ;)
 
I'm guessing that is a LiIon battery.

Lithium Iron Phosphate is much safer.


The experimental guys are already using them and I hear that Concorde is working to get an STC

http://www.aerolithium.com/
 
dmspilot said:
Wasn't there a problem not too long ago with iPhones catching on fire? ;)
Click to expand...

I believe the more well known one was the Sony manufactured laptop batteries. I didn't hear anything about the iPhones.

Consider you're also manufacturing literally millions of these devices that are being used by Joe Schmoe (who knows nothing of how they work and does not need to "take care of them"), the incident rate of failure is pretty low.
 
I don't know all the details of the incidents but, as with the NiCad batteries on previous airliners such as the 777, they are encased in a steel box which I am pretty certain was designed to contain a complete thermal run-away. So, although there was an awful lot of smoke, it looks as though the containment worked and the battery material itself was completely consumed without breaching the box. I would imagine that tests of this scenario had been conducted prior to production. I did read that use of the LIB's did require special certification procedures for the FAA to buy off on the idea.

Bottom line is that, worst case scenario it probably wouldn't have resulted in a fire or brought the plane down.

Not to say that it wouldn't have freaked everyone on board out to no end. :yikes:
 
They are heavy, cheap and simple. I will take my 25 lb Odyssey AGM anyday over that mess until all of the bugs are worked out. That box appears to have insulation on the interior. The blue nylon carrying strap survived. Look at all of the small thermistor and voltage sensing wires and those big bus bars/cables that could easily handle 200 Amps.
 
I was informed by an auto engineer that part of the reason these batteries are so unstable is because they have very specific charging requirements. A slight overcharge when the battery is at full capacity, and even small variances in voltage and/or amps while charging are all causes of the batteries overheating and then catching on fire.

A plane and RC builder who uses Lith Ion batteries told me that he's never had an issue, but he always worries about them, and doesn't use them as much anymore because of the potential dangers.

The WSJ kind of backed up this story when they reported this. I don't remember the exact wording they used, but it was something along the lines of these batteries being unstable if the proper charging conditions weren't met, and Boeing had experienced difficulties earlier getting the charging and computer systems to cooperate.

Just what I heard/read...if that's all true, I wouldn't put them in my car, let alone a plane. My phone is a different story. Small enough, low power, and not immediately risking my life. I'm pretty sure I'd feel the heat and smell something before my cell phone bursts into flames.

And I didn't look into it, but are these the same batteries that automakers are experiencing fires with in their hybrids? Yikes.
 
Sad thing is that over the years we have lost a lot of freight dogs to lithium battery fires in flight.....I am a fan of Boeing, but a bit surprised they haven't figured this one out yet.


Sent from my iPad using Tapatalk HD
 
I'm sure they have exhaustively done their carbon fiber home work as well as the LiO2 battery homework? Too soon to tell.
 

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Capt. Geoffrey Thorpe said:
That's why I'm buying one of these next time: http://www.ballisticparts.com/products/batteries/12cell.php

"The lithium ferrous phosphate used in the EVO2 battery is very stable and exhibits none of the thermal run away properties of Lithium Polymer batteries found in lap tops or phones."
Click to expand...

I've got a 4 cell in my little Honda Rebel and a 6 cell in one of the BMW F650GS's. As the need arises, the entire m/c and cage fleet will have these in them.

This is the four cell. Weighs about half of what the Monster drink does.

67d43e39.jpg
 
The battery in the Cardinal RG is in the tail, behind the baggage area. That's a pretty aft station. Even with the standard lead acid battery if you have a lot of weight up front you need to watch the forward edge of the CG envelope and might need to add some ballast into the baggage compartment. I'm not very heavy but with me and my CFII (185 or so) we're very close to the front edge. I wonder how much worse this would get with a lithium battery.
 
Capt. Geoffrey Thorpe said:
Lead acid is risk free: http://www.rayvaughan.com/battery_safety.htm

Particularly lead acid aircraft batteries: http://mechanicsupport.blogspot.com/2010/05/aircraft-battery-explosion.html

That's why I'm buying one of these next time: http://www.ballisticparts.com/products/batteries/12cell.php

"The lithium ferrous phosphate used in the EVO2 battery is very stable and exhibits none of the thermal run away properties of Lithium Polymer batteries found in lap tops or phones."
Click to expand...

All stored-energy devices have some inherent risk.

Discharging your lead-acid battery to zero runs the risk of polarity reversal on one or multiple cells when being recharged. For most SLI (start/lights/ignition) batteries as used on cars, the lead plates will collapse if fully discharged and the battery cannot really be charged again. Other than the fact that it's filled with sulfuric acid, it's pretty hard to run into major issues.

Lithium batteries have more specific handling requirements (but the energy density is an order of magnitude better than lead and the power density is also very high). Lithium batteries can be easily destroyed by charging >4.2V per cell, discharging below 3V/cell at load, breaching the sealed casing, or excessive current draw. In normal operation, the cell voltages of each cell needs to be known. By series charging (as you would with a lead or NiCD/NiMH battery) it's possible to push cells to different voltage levels, causing some to potentially exceed 4.2V or go below 3.0V when discharged. Cells in other battery chemistries "peak" at a voltage and then start to drop with no real danger unless the charge process is using high currents.

Almost all lithium batteries you see for non laptop/phone use will have two plugs, one with 2 pins for main power, the other with however many cells in the battery + 1 (ground) for balancing the cell voltages when charging.


Obviously, phones, laptops and RC aircraft need the power density. GA aircraft have a useful load measured in hundreds of pounds, it's not a major concern.
 
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