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A very lucky pilot! (LI Iron Battery)
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Wow..
Simply astonishing. I was considering Aerovoltz battery after reading some favorable comments on LiFePo batteries on VAF. Now there is no way ...
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I cant tell if the OP is the original author of the linked pdf. Since this happened in March I wonder if the manufacturer has a comment about this incident. No mention of whether they wanted the battery back to investigate the cause.
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I am not the author. It would have expected the manufacturer to have requested the battery back and try and determine the cause. I have no knowledge if that has happened.
George |
It looks bad, but is consistent with other conclusions from VAF threads - put it in a stainless steel box and vent overboard. At least it did not burst into flames. And take an airplane with it.
Now the discussion about what set it off. . . edit: I stand corrected on the flames -after landing and exposing, it did have flames. I was referring to a burst cell case where the contents violently spewed gas, liquid and flames. This post was a bit tongue in cheek as I have posted previously that just because it has IRON in it (alone), does not make it safe. It can still have an exotherm, as exhibited here. The LiFePh chemistries have a lower peak exotherm temperature that allows case containment, but is still over 300C. I still don't believe we have a reliable installation and management procedure, short of the sealed, vented overboard, stainless battery box. |
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George |
Vent overboard? How about diet to save the 10lbs and put a real battery on board. If he were cruising anywhere near the altitudes I cruise at....he would have been in serious trouble. 17500 is a long ways from the ground with smoke in the cockpit. Especially in an aircraft like the -8 with the battery inside and I dont think it's very easy to stick your head out of an RV in flight like he was able to.
I've been on fire in race cars....it isn't fun. I simply can't fathom risking my life, leaving my family without me....for 10lbs, or 100 for that matter. |
United Airlines had trouble with Lithium batteries on their new 787's. FAA grounded them for a while. I think one started smoking on the ramp in Japan. Don't know what Boeing did for a fix, but it might be worth looking into. (I "think" something about a sealed box and ventilation is what I heard, but I'm honestly not sure)
Just a thought. |
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The Aerovolts IS LiFePo, and it would be very interesting to hear more facts on this incident.. |
Just a counter point:
Lead Acid batteries fail too. Last week, my brother had one on a charger that blew about 1/3 of the top off. I was talking to him on the phone when it happened, and I heard it very well over the phone. Not a smelly smoking mess with a fire. A big blast with the top of the battery case blown off. I don't know which will be the more damaging, or which type has the greatest failure rate. My RV-8 shed about 70 pounds when I removed the Mazda turbo rotary engine, and replaced it with a lightened parallel valve IO-360 w/ CATTO 3 blade prop. It now weighs 1035 lbs with wheel pants! Needless to say, the CG shifted aft. I removed the PC680 from behind the baggage bulkhead today. Now I can remove a couple of pounds of battery cable too. I never liked the battery being in the back, it's hard to get to it for inspection or replacement, and it's not really isolated from the passenger compartment. I'll put the battery on the firewall, low, and away from the fuel system. I'm leaning toward a LiFePO4 with built in charge management circuits. I'm open to the idea of a vented case and/or a battery temp monitor. |
I also fly large scale remote control control gas and electric planes and helicopters, LifePO4 batteries have been extremely stable for all of the RC world but the majority of us balance charge our batteries for longevity. In the RC world life batteries have a nominal voltage of 3.3v/cell, different than the aerovoltz but the principal is the same.
Have you ever balanced charged your aerovoltz lifepo4 battery? Over time you can get a voltage differential between the cells which during the constant charging you could get a cell or two with elevated voltages that could lead to a cell failure. The aerovoltz website does mention the periodic balancing of the cells. http://aerovoltz.com/av_mgt.html |
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I agree with others... I'll stick to traditional batteries. the risk vs reward on this one is off the charts. |
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Have a read of the NTSB final report on the B787 battery fire in Boston here: http://www.teslamotorsclub.com/attac...2&d=1417522601 My personal stance is that I will not allow any large format or high-power capacity (more than a cell phone or ipad) lithium ion batteries of any chemistry in or on my airplane. Especially one that I can't chuck out the window if necessary. I suppose I do need to think about how to throw a cell phone out of my slider canopy if it were to vent. Over on the RV10 forum there was some talk recently of lithium ion battery powered jump-starters. They're certainly attractive from a weight and power perspective, but in my opinion are even more dangerous than a lithium ion battery mounted on the firewall because one would most likely store it in a flight bag inside the cabin. |
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Causes of battery failure
I don't know. I'm with Paul on this?.. let's wait for ALL the details. The pictures and story are a little suspicious. How many of us can just open a hatch and remove our batteries? Any hold down clamps? Maybe a cover or strap to remove? If I was to guess, this battery was sitting in a tray and just vibrating away for, who knows how many hours?.. MAYBE a hole got worn through the case, maybe something external shorted it out? I don't know. But, let's just get rid of all these nasty LITHIUM batteries ?.. I don't know, maybe all these "homemade" airplanes should be grounded?.. Just kidding, of course, but let's not let mob mentality take over.
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I heard that a car crashed last week. No way am I getting back in another car. They're dangerous.
Folks, let's see what the cause was. Lithium doesn't always equal fire, smoke, or an emergency. Done correctly it can have great benefits. This is experimental aviation, something I think folks forget about. We all have varying levels of comfort / risk we are willing to fly with. Those levels should be respected by everyone, not slammed because they aren't the same as your own. Flying is inherently dangerous, we just mitigate the risk and accept the rest. I for one will put a LifePo battery in my 10, safeguarded as much as possible and accept the risks just like other key components in my plane. |
Some years ago I had a new Yuasa battery blow its top off in my Harley while on a ride. Did about $5000 in damage. I contacted Yuasa, they sent me a special container to ship it to their lab for analysis. Surprisingly enough they claimed responsibility, saying they had a bad batch of batteries and the one I had was one of them. With the letter there was a check for all the damages. This Yuasa was a common lead acid battery. Point is, there's no 100% safe battery made. The first generation lithium ion batteries were unstable and got a bad reputation but there's different chemistries now with lithium, mostly very stable..... That being said, there's still some growing pains with this technology. With any battery, there's a tremendous amount of instant energy sitting there in your battery box. If something goes wrong they all have the potential to China syndrome.
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I completely agree. While some talk about risk analysis, I suspect it's more of a casual term rather than a serious look at the situation. When I replaced the PC-680 with a Shorai LiFePO4 in my -6A a year ago, I was quite content with the risks and mitigations as identified via an FMEA exercise. |
I'd wait for the full analysis if there is one before pointing fingers but the report brings home the effects of what can happen if there is a Lithium battery fire. Make no mistake, if this happens to a cabin mounted battery in flight without proper containment and venting, you will be incapacitated within seconds.
You cannot believe the amount of smoke and soot that one of these can produce when things go wrong... Design accordingly. |
Here is a update on this event:
Now that some time has passed I wanted to update everyone on the battery fire issue. This week we repaired the airplane, making a new hatch door, and relocating the battery installation from the nose to the under engine compartment. We installed an Odyssey battery. We did not replace the regulator yet, but did correct the ground wire connection that was burnt, running both power and ground wires from the regulator directly to the battery terminals to ensure a good connection. Removing the extra battery cable saved a few pounds. The odyssey battery weighs 13 lbs, so a lot more than 3.5 lbs, but a lot less than what he had. Moving the location really put the CG where we wanted it. This morning, Monday, I flew the airplane down to West Virginia. What I discovered was that with the Odyssey battery, the voltage was rising, right past 14.4 and on to over 16 volts before I turned on the landing lights to load it back down to a safe voltage. The landing lights draw close to the output of the charging system, or possibly even more. So that kept the voltage down under 12. There is no question now that the regulator is bad. I think that we can reasonably assume now that the regulator is the cause of this incident. What I find very interesting though is that when the Lithium battery was installed, the volts did not exceed 14.4. I think Jim Showker might be on to something here in that with these lithium batteries they simply cannot absorb any energy past a full charge, they simply began to overheat and if it continues, start a thermal run away. A 13-20 lb lead acid battery has a lot of thermal mass and can absorb a lot of heat, plus water boiling away dissipates a lot of heat as well if it is a flooded battery. So it is very conceivable that a lithium battery would be very vulnerable to an overcharge situation. But also, it may be that with a lithium battery there will be little indication of over charging. It seems that the lead acid battery will allow the voltage to go right on up, where possibly the lithium battery is absorbing that energy thus keeping the voltage down, not indicating an overcharge condition on the voltmeter. I don't know this to be true for sure, but it certainly appears to be the case. I will discuss this with Aerovoltz and also see if we can find some solid solutions to prevent this. Steve, the owner of Aerovoltz did call me today, but I was on a flight to Sun N Fun and could not take the call. Hopefully I'll catch up with him soon. The owner of the airplane has a key west on order and will install in ASAP! So, in conclusion for now, I think we can determine that overcharging is the cause of this incident. The el cheapo junk regulator was the culprit. Using these batteries can be done safely in my opinion, however, I would only use a very good quality regulator like key west, and consider anything above 14.0 V to be dangerous. Monitoring system voltage is a must in my opinion. And still might not be a bad idea to consider the possibility of thermal runaway on one of these when you install it. Being able to easily access it and throw it overboard would be a good idea. Keeping it away from anything flammable. Having a way to shut off the charging system in the event of an over voltage should be considered also. As long as they are not over charged there should be no issue. The questions then become, if it is overcharging, will you know it, and if so, what will you be able to do to remedy it. Remember it only took 30 minutes from a cold battery to on fire. Over voltage has to be able to be detected and remedied quickly in flight. |
Thanks for the followup! Over voltage/over charge is the Achilles heel of the Li batteries.
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This discussion and those like it are public and easily found. An attorney fresh out of school will be calling the failure and its consequences easily foreseen...and your build not only liable but negligent. My job requires daily and constant risk analysis. I've dealt with those attorneys and had to defend my actions. It's less than enjoyable, and I had done everything right with no liability. Defending this battery tech would be significantly more difficult with all of the failures out there. Sure, the FAA allows it under experimental conditions but that does not release you from liability. It places that liability directly on you the manufacturer...and your family....and assets...and future assets. Sit down and think worst possible scenario versus best possible benefit. Worst....you kill yourself, your neighbors grandson who you offered a ride to and a school bus filled with children. Best possible benefit, you climb an unmeasurable amount faster and your W&B has a slightly smaller number on it. If a battery is significantly affecting your weight and balance or carrying capacity...you've built something wrong. |
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Eliminating risk isn't the point. Minimizing risk is. |
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When looking at problems like these, you need to look at risk TRADES. I was a firefighter for several decades, and saw a lot of lead/acid battery explosions in vehicles - so they happen as well. It is not a case of zeroing out the risk by not using a Lithium-based battery. There is risk the other way as well. To quote that (now) old movie..."Interesting game - the only way to win is not to play!" |
If you're going to use a lithium battery in your plane, please get one with a built-in Battery Management System (BMS).
A BMS would have likely prevented this fire by disconnecting the battery cells once the voltage started to run away. EarthX batteries do have a built-in BMS and others may also. The Shorai and Aerovoltz do not have a BMS. Fly safe, David |
Couple of thoughts...
Bad Regulator => Over volts => (non BMS) Li battery = issue (probably). Firstly, whilst the OP puts down to a poor regulator "and now has a good one", it would seem more important (and not just for the battery, but avionics) is a OV unit (Crowbar?) - which some alternators (e.g. PP) have built in. Secondly, most of us in RVs have fancy EFIS/EMS systems. Seems there is scope for ensuring there is a red warning / alert / noise at as low a Voltage as you can set in Normal Ops. Then even the first sign of rising voltage gives you a chance to shut off the Alternator. As Paul says, it's risk assessment and mitigation, the ultimate of which is "don't fly" :eek: There are lots of Li batteries flying, very few incidents, but anything that can be done to "trap" those incidents before they become hazards has to be a benefit ;) |
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I appreciate your concern for risk management - too often we see examples of TLAR ("that looks about right") engineering that has obvious risks with no mitigations. That said, I find that hyperbole ("plummet into a house or school") to often be a sign of persuasion through fear, not knowledge. |
Folks, if you are considering a lithium ion battery of any type in your aircraft or other vehicle, do yourselves a favor and read the recently released NTSB report on the JAL 787 Yuasa battery failure. It includes information related to two other lithium chemistry battery failures on the 787 fleet.
http://www.ntsb.gov/investigations/A...s/AIR1401.aspx Read the report *fully* and understand its implications. While lithium battery chemistry does not equal certain death and any sort of high density energy storage device can be said to be dangerous, this report details some important points to be aware of. I won't get into the details of the report, because I feel it is important for experimenters to fully understand for themselves the issues raised. That said, the report deals with several potential root causes they considered, all of which are important to consider and address in a battery installation. One particular detail I will mention is that of wrinkles introduced by the cell manufacturing process in the individual cell windings. These wrinkles possibly resulted in internal short circulating of at least one individual cell in the battery, which led to thermal runaway (exotherm) of that cell, cascading to most of the other cells. Failure modes such as this can be independent of the specific chemistry of the battery. I make no claims to special knowledge on the topic, and I still am undecided as to whether I would use a lithium cell battery in a project, but I encourage folks to read the report. I certainly learned a lot about battery manufacturing and the details of lithium cells in particular. |
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A much better link for learning about the characteristics of lithium chemistry batteries will take you to Battery University: http://batteryuniversity.com/learn/a...of_lithium_ion |
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EarthX has done many of these tests on cells and packs with the BMS. Whether these tests, alone, sufficient to yield a drop-in replacement is unknown, but they did not just make a pack for sale. Along with a sealed box, (a vault) and crowbar circuit for runaway voltage regulator mitigation we just might have a winner. Regardless of testing, until there is enough volume and usage, and quality control all along the line from raw materials to the completed pack, we should be careful. Don't expect that it is an on the shelf, blister pack, use it anyway you want and sue the manufacturer when it fails product, not yet. And, maybe never for aviation. We ARE experimental, so care, learning and understanding should be taken in the application of everything we do. Never be complacent. Never stop questioning, and don't discourage (please!) those who do. Sorry, that was not intended to sound like a lecture, just some thoughts on the subject. |
BillL, I agree with what you've written. The NTSB is often circumspect in its conclusions when the data lean in a direction but there is not conclusive evidence of a specific root cause.
When you say that it is implied that Boeing was naive and placed too much trust in its contractors' processes I agree, that was my take as well. The battery manufacturer as well may have had the chemistry down pat, but the mechanical flaws introduced in the assembly process may have contributed to the failure. As experimenters, the individuals in the community here take on the role Boeing had as a systems integrator, and need to exercise skepticism and good judgment when selecting suppliers. Probably too much of a lecture here as well. I really want to see light, high density power supplies succeed, but success implies safety as well as performance. One other note...if you take the "contain it and vent it" approach to risk mitigation, make absolutely sure the materials you use in your containment and vents are suitable for the environment surrounding a runaway battery. |
I'll probably be dead soon!
I've got a Shorai in the front baggage compartment of my 8. However, it is in a stainless box, I have my EIS set to alarm for an over voltage condition, and I have a very small alternator (SD20 only) which will likely fry itself even before the crowbar fails.
I am not going to get rid of the Shorai, but having read this and using the 'just in case' rule, it will soon be moved to the firewall as low and cool as possible. That's enough caution for me. If I want to rule out every possible battery incident, I'll fly my no-electrics Biplane. But then I have to hand prop... |
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Charging?
If the Challenger had a Rotax 2-cycle engine, which is very likely, the charging system is not the most sophisticated. I suspect the battery was being overcharged, and apparently that battery is not as tolerant of this as a lead-acid battery.
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Lets hope you are NOT dead soon!
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I just wanted to pass along an idea for those with LiFePo4 batteries--In addition to monitoring voltage (which I think is critical), I've also installed a couple of surface-mount thermocouples to monitor individual battery temperature.
If either parameter goes out of limits, I plan on disconnecting the offending battery from all charging or load. So far so good, and I wouldn't feel comfortable experimenting with a low-volume technology without the added data. |
Bill is on the same page
Hey Bill, that's what I'm planning. Battery forward of the firewall, with forced air cooling. I'm as concerned about battery longevity as anything else.
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