There are many details not here to evaluate all the factors that lead up to this event but ANY lithium battery used with a Rotax 503 should not be used as they are not compatible due to the how crude the charging system are in these engines. To compensate for the design issues, Rotax uses a large capacity lead acid battery with this system (minimum of 16Ah) as a lead acid battery is much more tolerant to voltage irregularly. I would suspect the lithium battery used here was also severely undersized but I do not know that for a fact.

I also do not know any details about which particular battery manufacturer this is, but it is possible there were no warnings given about the use with this particular engine which is why I wanted to respond to this thread as there was warning signs prior to this event from the battery itself which will apply for any users of a lithium battery or lead acid batteries that need to be heeded.

First, any lithium iron phosphate battery that reads 10V needs to be evaluated before continued use as the odds of permanent damage to the cells at this level of discharge is very possible. What should have been done instead of jump starting the battery, is a slow amperage charge (around 2 amps) from the recommended charger from the battery manufacturer. If the battery did not charge on the charger, it would immediately alert you to a problem and to discontinue use. Never use a battery that will not accept a charge, no matter what the chemistry.

The second thing here is the fact the battery remained at a severely discharged state, and was used within a charging system that has poor voltage regulation. Do not do this with any battery, lead acid or lithium. Never try to use a battery that will not accept a charge.

All products have limitations and the continued use of a product that is defective can and will have a poor outcome. A quick example is continuing to fly your plane when you know that you have a gas leak, or you have bad tires for landing.

As EarthX was mentioned in this thread, I also want to point out that the EarthX aircraft specific batteries not only protect from the over discharge, over charge, short circuit, excessive cranking and cell balancing technology built in that is redundant, they also have an LED battery fault light indicator that alerts you with a solid or flashing light when you need to evaluate your battery as a possible problem exists. You must heed any warnings as they are there for a reason.

I understand the mistrust of lithium batteries in airplanes, and have shared this skepticism in the past. However its also interesting to reflect on how much energy is packed into your fuel tanks, and how dangerous it can be if not managed properly. By my calculation one gallon of gasoline contains roughly the same amount of energy (in joules) as about 250 batteries (assuming 12v and 12 a.h.). If a 12 a.h. lithium battery weighs 3 pounds, this means that you?d need 750 pounds of battery to equal 6 pounds of gas. Small wonder we don?t have practical electric planes yet!

I don't think that's a useful comparison because unless the gasoline is mixed at the right ratio with air, it won't have that energy capacity. You might say that a gallon of gasoline combined with roughly 1,200 cubic feet of sea level air, then it has that much energy.

If I understand it correctly.

Kind of like the difference between a jet engine and a rocket engine. One needs a lot of air and the other doesn't.

Dave

Don't get me wrong, I'm a fan of the (developing) lithium battery tech - but fuel tanks show a surprisingly low propensity toward bursting into flame than lithium batteries (so far).

No, it's not apples to apples - and that's the point - in the age of the Wright Brothers fuel tanks were much more likely to cause problems than they are today - and so were the engines. Technologies mature over time, it's the nature of the beast. Give this one some time to work out it's kinks and we may have something useful. Nobody is requiring you to install it if you don't want to - that's the great thing about Experimental category.

I think you're correct assuming all of the energy has to be released at once (a fuel-air explosion). However I don't think this is the right comparison since the lithium battery didn't explode, it burned. You can certainly release all the energy in the gasoline if its allowed to burn more slowly.

My electric plane comparison wasn't quite right because only about 25% of the energy in gasoline can be converted into motion by an aircraft engine.

I think anyone who has had a fuel tank rupture after a crash would strongly disagree with this statement (unfortunately many are unable). There's also been at least one RVer that I can recall who came to a tragic end due to an inflight fire.

I'm not 110% comfortable with lithium batteries myself yet, except of course the ones in my phone, watch, two laptops, RC airplane, etc... However I think my probability of being injured by a fuel tank is likely higher than being injured by a lithium battery. Hard to prove this of course since not many lithium batteries in service yet. I'll certainly watch mine carefully. I'm not that concerned however by reports of problems with batteries that are of a different design, that have been misused, or both.

Good point. But how will you know when the technology is "safe enough"? The Wright brothers had a 50% chance of dying in their creation; surely we're far beyond that point with lithium batteries. Lithium batteries in one form or another have been around for what, 50 years? They will never be 100% safe. Neither will gasoline, lead-acid batteries, or airplanes in general.

Good point as well concerning experimental aircraft. I have plenty of friends and acquaintances who think I'm taking an unreasonable risk every time I fly! The freedom this category provides is extraordinary.

Not for me
 

As holder of a patent concerning li ion batteries, they are not for me. I just dont see the advantage being great enough to offset the risk for a gas powered rv. Now if you are talking an all electric plane that would not get off the ground without a li ion battery, that is a different story. But i know of no RV that could not fly without li-ion. JMHO

It takes the same amount of air to burn a gallon of gasoline regardless of the rate it burns. The air is the oxidizer and the gasoline is the fuel. Both are needed for combustion.

Dave

Dave,

We agree on that; I think I missed your point earlier. The gasoline poses no risk so long as it stays in the tank/fuel lines. My point is that sometimes it doesn't.

Hmmmm. As I have earlier questioned L-ion battery safety, and was met with enthusiasm over EarthX (I own one) but I am still weary. Some say that because of their chemistry and protective circuitry they are safe.

Have a look at this though:

http://www.avidfoxflyers.com/index.p...ttery-warning/

Thoughts?