What's the fire risk?

I have seen some pilots say they wouldn’t fly the SP140 nor develop a similar unit because of the fire risk. One mentioned that they had used LiPos a lot for RC stuff and they had heard about too many fires in that realm. Is this a valid concern for the SP140? Have there been any issues with any SP140s so far? Is it more likely to be a problem as the batteries age? Thanks!

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The short answer is yes there is a fire concern for using lipos in general.
However, far and few between are fire issues and most of the circumstances are under a physical damage issue. I would have no problem using these packs.
I would order them but I have decided to venture into a DIY pack this winter as I have more time than money.

Paul or Zach can confirm but I think the SP140 battery is comprised of 18650 LiFe - round cells like your power tools and earlier Tesla cars. There is always a risk when a lot of energy is stored in a small package. But these cells are a lot more robust than the pouch cell type LiPo cells used in RC. Those pilots wouldn’t fly with those cells but they’re OK with the holding them in their hand in a power tool.

LiPo cells are used in cell phones, RC models and drones because they have the highest power density. Lot’s of power in a very light package. But these cells are more dangerous if damaged or overheated, or overcharged. Are you nervous that there is a LiPo pouch cell in your pocket?

It’s all about knowing the danger and understanding the risk. I’m flying 8 Bonka LiPos. Personally I don’t see the risk of a LiPo “vent with flame” event in the air as a bigger risk than all the things that can go wrong with a 2 stroke engine.

The sp140 uses 21700 li-ion cylindrical cells with an NMC chemistry (LiNiMnCoO2 chemistry to be exact). It’s not quite as safe as LiFe chemistry(LiFePo4 to be more precise) because the LiFe chemistry has only a 3.3 nominal voltage which decreases the fire and explosion risk during battery failure. On the other hand a li-ion has a 3.6 nominal voltage. This greatly improves energy density, but under cell failure it is not quite as safe. So because the sp140 needs a high energy density battery that cannot be provided by a LiFe chemistry and the li-ion cells are still pretty safe, it uses Li-ion cells.


if you want security with eppg you have to buy batteries which are UN 38.3 approved.

as an example a link. or you build your own batteries according to these standards.

if you buy batteries or complete eppg that do not have any certificates you have to trust that everything is ok. li-ion is very safe and is widely used in aviation.

lipo from the hobby area is very risky.

the lipo manufacturer also forbids it. an exception are industrial kokam cells for aviation applications.

LiFe for aviation is currently only possible with trike. Too heavy for the start of the footlaunch.


because the system was built and developed by experts and is certified. there is no manufacturer worldwide of hobby lipo that are allowed for aviation. if diy eppg people use lipo this is not a “system” that has been tested. it is purely an act where the user is 100% responsible for the risk.


I have heard these remarks before too. Usually they are flippant one liners tossed out by people ignorant of lithium chemistry. Firstly, gasoline is definitely very flammable so they already are flying with a potential fire risk. In fact making fire is how ICE paramotors get their energy!

The problem is that people hear the word “battery” or “lithium” and immediately they think of the LiPo starter batteries they know of which can go thermal if physically damaged or overcharged and seem to be the ones with the most dramatic videos on youtube. The battery pack in the SP140 does NOT use this chemistry.

There are many variations in lithium chemistry for batteries with the safest (from a fire standpoint) being LiFePo4 or Lithium Iron Phosphate. If these are abused, the worst they do is just ooze their innards.

In 2017 the FAA did a fire hazard analysis on the various lithium chemistries. This predates the 21700 cell found in the SP140 however the analysis did include the 18650 cell which I believe has a similar chemistry but again even in this cell type there are variations such as the Tesla versions that utilize silicon in the anode for improved performance.

The chemistry of the SP140 is lithium nickel manganese cobalt oxide as stated in a post above.

For those concerned about the fire hazard, this is an interesting read. You can find the report at the link below.

And and a partridge in a pear tree…:rofl:


In the early days of X4 some pilots had a jettison system for dropping the LiPOs in the event of a fire. Seemed a good plan but this seemed to be abandoned due to maybe the system not being very reliable plus I think the consensus was that the fire risk is extremely low in flight. There is more of a risk when charging or particularly if damaged. I am just at the stage of mounting the batteries on my X4 kit and I’ve gone with the 3D printed rails but I might add a bit of fireproof material between the pilot and the batteries.

Is not the same risk with fires in oil liquid fuel?

Hi totuma

The risk is different of course. Both extremely low.

The thing with internal combustion engines and fuel fire risk is that we have 100+ years of use and abuse. We all grew up around cars and other ICE powered equipment. We’re all very familiar and comfortable with the risks and how to handle gasoline so that it doesn’t go boom (and it does go boom). Basically ensure there are no open flames or sources of ignition near a refuel operation or a container and you’re good.

LiPo batteries are a relatively new thing for most people - cell phone experience not withstanding. They can vent with flame (burn violently but not explode) if they are damaged, shorted, overheated or overcharged. The latter two require some serious intent or very poor attention. Verify and supervise the charge operation. Ensure it can’t run over. Size the battery correctly for the load. Don’t charge a damaged battery. Use plugs that are covered to prevent accidental short.

Thanks, everyone!

BOEING, the jet airliner manufacturer, had a problem with Lithium batteries.
They caught on fire and caused some problems.
Their fix was to enclose them in metal boxes. That apparently satisfied the FAA
so the jets could fly again.
Sorry, I didn’t see the actual memo so I can’t tell you what the chemistry is but I know what the fix was.
The only thing I can say is I have seen a Lithium Battery fire and they are very hard to put out. They are almost as stuborn to put out as a metal fire. For those who have not experienced this, you have to use a special extinguishment powder to put the metal fire out. Water won’t do it.
Just saying.

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