Battery safety is no joke. In late 2017, we did some independent testing of our own and found that while LiPos are generally very stable, they’re also capable of substantial damage. Most pilots seem to understand this and take it seriously, but there often isn’t a similar amount of care taken when it comes to the batteries for micro quads. Don’t make this mistake.

Conclusion

Because this is a safety article, I’m going to drop the conclusion right up front. Even very small LiPo batteries can be dangerous if not treated properly. Care should always be taken in handling and storage. Use an appropriate container that is actually designed for fire suppression, and make sure you are charging at the proper settings.

Testing

These were controlled tests following a procedure approved by local fire officials. Many safety measures were taken before, during, and after testing that are not visible here. Do not attempt to replicate these tests on your own.

These tests used 250mAh 1S “stick”-style Lipos, made popular by the Inductrix, Tiny Whoop, AcroBee, and other micro quads. For our tests, we overcharged a single battery until it failed. Overcharging might cause a battery to fail more spectacularly than it would otherwise. While an overcharge is nearly impossible while in storage, it’s definitely possible to accidentally set your charger to an incorrect setting. We also don’t have a controlled and reliable method to induce thermal runaway under more typical storage conditions. If you search for them, stories can be found describing similar fires as we had below without any overcharging.

Open-Air

It took less than a minute to go from being fully charged to causing a thermal runaway. The battery puffed until it could no longer hold the pressure. When the lining burst, the pressure propelled the battery off the test plate, giving us a brief look at the red-hot interior. Flames erupted soon after, reaching 12–18in high and lasting for around 10 seconds.

The battery fire itself doesn’t appear life-threatening, but nearby combustible materials could catch and lead to a larger fire. The battery’s ability to propel itself elsewhere is a concern, since it might leave your charging or storage area and catch fire to something else.

Tiny Whoop Battery Fire Testing: Test container open with batteries inside

Container packed and ready to test

Foam-Lined Storage Container

Many micro quad pilots carry their batteries in a foam-lined box, and these cases are readily available from a number of respected brands and retailers. Do they work? Our answer to that is mixed. We tested the style with thicker, clear sides, a rubber seal, and spring-loaded lid. This case was packed with nine similarly-sized batteries.

Again, the battery breached in less than a minute while using incorrect charge settings. This battery didn’t visibly erupt in flame, but certainly generated quite a bit of heat. The battery melted the side of the box enough to cause damage to anything on the other side, and melted straight through the bottom of the box completely to the concrete pad below. The foam inside the box made a mess, but prevented any other batteries inside the case from bursting—though they would all be a loss and not usable again. The rubber seal on the box didn’t function at all. From what we know about sealing ammo cans (don’t!) this is actually to its benefit.

Tiny Whoop Battery Fire Testing: A hole melted through the bottom of the box Tiny Whoop Battery Fire Testing: Side of test container is melted and discolored Tiny Whoop Battery Fire Testing: Inside test container with melted battery Tiny Whoop Battery Fire Testing: Foam battery separator is melted near battery failure

Is this a success? Nearby combustible materials could still catch fire. I would not recommend keeping the box on a desk, shelf, inside a backpack, or anywhere else where it might touch something that you value or could catch fire. On the other hand, if placed on top of a fireproof surface, this box would prevent failed batteries within it from spreading fire outside—and that may be enough for the way you charge and store your batteries. It’s obvious to us that these batteries should be treated with care, but this box is not meant to provide any kind of fire protection. For that reason, we won’t be recommending it as a general rule—it’s too easy to forget safety precautions when the batteries are already stored so conveniently.

Tiny Whoop Battery Fire Testing: LiPo bag ready to start a burn

The LiPo bag didn’t do well in our larger battery testing, but what about a much smaller “tiny whoop” battery?

LiPo Safe Bag

In our larger battery testing, we found that even a 1000mAh battery would burn a hole in a LiPo safe bag and damage anything nearby. But a 250mAh battery burns considerably shorter, so we put it to the test in this common storage container. We packed a handful of similar whoop batteries around the trigger battery (some of which survived the earlier box test) to see how they would hold up as well. This test was done on a different day, but the process was the same.

The LiPo bag held in the flame—not much more than a few puffs of smoke escaped during the burn. However, even a tiny whoop battery gets hot enough to melt the bottom of the bag, which would damage whatever it was sitting on. The other batteries that were packed in with this one puffed significantly, but didn’t ignite.

Tiny Whoop Battery Fire Testing: Inside of LiPo bag shows heavily charred area Tiny Whoop Battery Fire Testing: Outside bottom of lipo bag has a burn mark where the bag melted Tiny Whoop Battery Fire Testing: Other batteries in the lipo bag puffed but did not ignite

Much like the plastic container, whether or not this was a success depends on what you’re expecting. You probably could not start a fire this way unless you set the bag down on something readily combustible, but you may ruin that surface regardless. Don’t consider your LiPo bag fireproof; it’s not going to prevent damage altogether. If you adjust your expectations and store the bag on a fireproof surface, it may be safe enough. We still don’t like that the bag gives a false sense of security, and there are certainly better options—but don’t feel too bad if you travel with small batteries inside a LiPo bag from time to time.

Wrap Up

Even small “Tiny Whoop” batteries should be treated with care. While they may not fail as spectacularly as their larger brothers, they are still capable of starting fires. Store and charge them in an enclosed—but not sealed—container, away from any combustible materials. These batteries don’t emit a lot of flame and smoke, but are still capable of setting off a chain reaction with other batteries stored together. While the LiPo safe bag and plastic/foam battery boxes provide protection from flame, they can’t be relied on for complete protection on their own. A ceramic tile or concrete pad—for only $2 at the local hardware store—could go a long way.

If you’re interested in finding a product you can trust, we recommend looking at the Bat-Safe.  Again, check out our detailed battery container testing for info on safe storage methods.  Whatever your method, set up a safe storage area and always follow proper charging procedures!

If you are interested in reading more about battery safety, you should check out this series:

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