Lithium Battery Fires?

[John DeRosa]

I have heard of several EV motor gliders having their lithium batteries catch on fire.

But I don't think that I have heard of a pure glider having their much smaller capacity lithium battery (9Ah, 12Ah, etc) catch on fire.  Not to mention the even smaller lithium batteries found in a portable devices we carry in our cockpits (i.e. Oudie).  

Anyone know of any reports?  

Thanks, John (OHM)

[Cliff Hilty]

Hi John, if Im not mistaken the lifepo4 are a lot safer from that happening as compared the hi energy output li-ion needed for self launch or sustained electric motors. And no I have not heard of any mishaps yet! My K2 and Dakota batteries are from 2017 and have no noticeable diminished capacity so far! 

Cliff

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[Mark Mocho]

In 2017, the FAA published a study on the hazards of Lithium chemistry batteries. Comparison testing showed that LiFePo4 cells were the safest chemistry by far. The study is attached below.

[krasw]

I know of one incident where EB-28 small LiFePo4 battery caught fire mid (gliding) flight. Luckily airport was very close so pilots managed to land safely within minutes, with smoking battery causing heat damage to structure behind engine bay. It is unclear if the fire was caused by faulty BMS circuit setting plastic encloser to fire or cell overheating, my guess is the former.

[Andrzej Kobus]

Do you have any sources for this?Are you talking about the early removable packs in FES gliders?

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[krasw]

Yes I have source, the glider is based at my airfield and I know the pilots very well. 

Please google what is EB-28. 

[Tango Eight]

More detail would be great.  
T8

[krasw]

What detail would you like to know? The smoking battery was removed from glider after landing. I believe the EB has smoke alarm in engine bay, though I am not sure.

Risk of flying with LFP batteries is low, but never zero. I have LXNAV battery monitors installed, maybe they will give heads up before something catastrophic happens. 

[Ian Molesworth]

A smoking battery is not a propagating fire. Very different.

Some post analysis of the cause and current damage to any structure
beyond the battery would be nice.

Although LiFePO4 cells remain relatively cool when thermal runaway is
induced, the cells are capable of generating huge currents which could
cause wiring to catch fire.

It really does need mode data!

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[Scott Fletcher]

If your glider battery starts smoking, it will be canopy jetison at a minimum, probably get so excited you bail out if you have enough altitude, because its going to seem like it's on fire.  We had one lithium ion battery cell about 2" in dia 4" long mounted in a plexiglass box on the test bench for power line vibration recorders.  It didn't have a fuse on it when we moved the test stand from NY to SC, didn't look dangerous, just a big D-Cell battery...right.  Worked great for 4 years until the technician shorted the test leads.  It didn't explode or catch on fire, just off gassed.  Ended up evacuating a 250,000 Sq Ft building with, 150 people working it it.  We got to meet two entire fire departments in the parking lot and a hazmat team. So fuse as close to the battery as possible, treat it gently, if it gets banged around, replace it.  SLA batteries are not particulary better at handling the issues that make the lithium batteries do bad things.  Small box, lot of energy and noxious chemicals in there, bad things happen if the magic smoke wants out.

I saw a glider on the ground, canopy closed, pilot in it.  side vent open Pilot flipped the master on.  There was a short in the wire under the seat pan, no fuse on the battery. Cockpit filled with 0 visibility smoke in 0.2 seconds, sure looked like it was on fire.  That was just from the insulation burning off of 3 ft of wire, the battery was fine.   Much excitement afterwards but no fire trucks that time.

SF

[Eric Greenwell]

The 12V LiFePO4 batteries we use should have a BMS in them that prevents "huge" currents, but the real limit is your wiring: it's unlikely the size you use for your instrument can survive the amps a battery can supply before the BMS kicks in, so use a fuse near the battery terminal, as recommended. My Bioenno 12V, 20AH battery has 5A fuse at the terminals.

The starter battery in my ASH26E has much bigger wires connected to it to handle the 100-150A currents the starter requires, and the EarthX ETX680 delivers. No fuse, but the glider does have a high capacity manual disconnect switch. I don't know of any pilot that's had to disconnect the ASH26E starter battery because of smoke or fire.

[Scott Fletcher]

Eric, 

I come from an industrial background where high current motor circuits without fusing would be a big no no.

Engine starter circuits starting with cars & stationary engines, then aircraft, do not have any fusing in the starter circuits.

The reasoning is that it is safer that way, not sure about that, but the deciders, decided that a long time ago.

The wiring and other components in the starter circuit are also significantly undersized for the load, compared to industrial wiring practices (NEC)

So when the manual says don't hold down the starter button more than 3-4 seconds, and allow some cool down time between subsequent attempts.

It's because all those undersized components start getting real melty, real quick after that.

I switched to all LiFePO4 batteries in my glider, the Earthex works great for the engine battery.

I'm hoping that the BMS board in the avionics battery turns it self off before the battery is destroyed 

By the idiot pilot forgetting to turn the Ilec off just prior to putting the glider back in the trailer.

It should, but I'm afraid to test it. 

Scott Fletcher

120 Ashmore RD

Greer, SC 29650-2926

C: 864-420-1749

E: 211fl...@gmail.com

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Subject: Re: [RAS_Prime] Lithium Battery Fires?

 

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[Moshe Braner]

By all means use a fuse.  I use a 10A fuse because 5A fuses tend to blow at random times (usually just as you're ready to fly) due to current spikes when turning on some avionics.

But also, when choosing a battery, choosing one with a lower-current BMS may be an advantage since it will shut itself down before the current gets very high.  It may be 30A or it may be 20A or even 10A - check before you buy.  The lower-amp ones are also cheaper.  And as the avionics battery in a glider you don't need more than 10A.  Even if it is a 30A BMS, in the case of a short circuit, the BMS will shut down instantly, before the wires get hot.

On Saturday, February 21, 2026 at 11:10:51 AM UTC-5 engre...@gmail.com wrote:

The 12V LiFePO4 batteries we use should have a BMS in them that prevents "huge" currents, but the real limit is your wiring: it's unlikely the size you use for your instrument can survive the amps a battery can supply before the BMS kicks in, so use a fuse near the battery terminal, as recommended. My Bioenno 12V, 20AH battery has 5A fuse at the terminals.  ...

[Ian Molesworth]

A fuse will protect the wiring from the battery to the rest of the aircraft .... a good idea.

It won't protect you from an internal fault in a BMS built in to the battery. Not much you can do about that. Fortunately the failure modes of the BMS's commonly used appear to be rather fail safe than fail ..... lots of heat. 

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[Charles Mampe]

We do fuses on the battery for all out gliders. I buy premade pigtails from Amazon with a automotive blade fuse molded in. I then glue (using Goop) the fuse holder to the battery top between the terminals. This keeps it low and allows a strap to retain the battery in most ships. Fuses are easy to find in many places and I usually use a 10A rating.

[upnaway]

In Australia a fuse as close as possible to the battery is mandatory under our airworthiness regs., regardless the chemistry of the battery. 
Incomprehensible to me why anyone wouldn't use one. 
The intent of a fuse is to protect the downstream wiring which as has been mentioned can cause plenty of havoc without getting anywhere close to causing the battery to malfunction.
We all have fuses in our circuits, it's just that some people have the wiring itself as the fuse. Select accordingly as you wish.
7A fuses seem typical and sufficient, but I guess it just depends on what you have between your battery and the next fuse. Often the switches are a limiting factor, 5A seemingly a fairly common switch rating. Certainly I consider the master switch should be rated at least as high as the fuse in front of it - I don't want my master to weld itself before the fuse blows.

We also have a requirement that of the lithium chemistries only LiFePo4 batteries may be used (not talking starter or propulsion systems here) and that they must be approved to one of a fair list of standards:
IEC 62133-2 Secondary cells and batteries containing alkaline or other non-acid electrolytes – Safety
requirements for portable sealed secondary lithium cells, and for batteries made from them, for use in
portable applications, Part 2: Lithium systems.
RTCA DO-347, Certification Test Guidance for Small and Medium Sized Rechargeable Lithium Batteries and Battery Systems.
RTCA DO-311A, Minimum Operational Performance Standards for Rechargeable Lithium Batteries and Battery Systems.
UL 1642, Standard for Lithium Batteries.
UL 2054, Standard for Household and Commercial Batteries.
UL 62133 Secondary Cells and Batteries Containing Alkaline or Other Non-Acid Electrolytes – Safety Requirements for Portable Sealed Secondary Cells, and for Batteries Made From Them, for Use in Portable Applications.
UL 1973 Standard for Batteries for Use in Stationary, Vehicle Auxiliary Power and Light Electric Rail (LER) Applications.

A pilot I know here found his approved LiFePo4 battery smoking on the tray behind the seat before take off. Some fairly hasty removal ensued, suspecting thermal runaway. In the end it turned out the canopy had focused onto the battery and set the casing smouldering. Once it was removed it stopped smoking, but was retired from service.

[krasw]

Before installing random size fuses to your gliders, please check current draw in normal operation. Fuse size is function of wiring cross section. For example, extracting turbo engine takes steady 7+ amps for over 10 seconds in my glider, even if avionics draw 0.5 amps.

[Scott Fletcher]

Starting current on an electric motor can be up to 5x  FLA.  It does not last very long but it's there.  So if you have an electric motor in the circuit, use Slow-Blow fuses.

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[Moshe Braner]

Also, the starting current of a motor may cause the BMS in the lithium battery to cut out, if the current is above its limit.  I use two "12V" LFP batteries in series, 7AH each, similar to what we use in gliders, with 20A BMS, to power a small electric mower.  (Originally powered by lead-acid batteries.)  It refused to start for that reason, even though the current, once started, is only about 6A.  To solve that problem, I added enough wire in series (zip cord coiled up, shorted at one end, to prevent it creating an inductance) to limit the starting current to what the BMS will allow.

[Ryszard Krolikowski]

I was early adopter of LiFePo4 from K2 , I think from 2010.

I know many of you don't feel this way, but LiFePo4 is way safer than acid. 

Acid battery has no thermal shot down sensor, no amp limiting shut down.

And I didn't figure yet out why, but I had 2 times already my acid battery explode in my RV. One time it happened 2 yrs ago, I was driving through the center of Houston on the way to Seniors .

Imagine you have acid battery exploding behind you head in the glider in flight.

Ryszard

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[krasw]

I have had 5 LiFePo4 batteries over the years, and failure rate of BMS circuit has been 20% so far. I have quite good confidence that LFP chemistry is safe for aviation use, and very little confidence that (mostly) cheap chinese BMS circuits manage to save the day. I do not thint LFP is safer than SLA battery, but I can live with the risk. The risk of not being able to extend turbo because of depleted SLA after long flight might cascade into something way riskier, so there is that.