LiPo fires are rare, but when it comes to battery safety, I can’t take chances—I’m a father of four. That’s why I’m reviewing the BAT-SAFE Battery Charging Safe Box.
Before you read this article, make sure you’re familiar with the hazards of charging and storing LiPo batteries. You might also be interested in how to charge LiPo batteries. We reached out to BAT-SAFE, and they provided the test units to us for this review.
According to the website: “The BAT-SAFE is an insulated double wall steel box that contains the fire and intense heat in case of a runaway battery. The smoke and soot is filtered through a flame arrestor.” Tom Mast saw that existing containers were inadequate, and set out to develop a reliable off-the-shelf solution.
At $60, the BAT-SAFE isn’t an impulse buy. Why would anyone pay $60 when an ammo can can be had for $20, or a LiPo Safe bag for $10 or less? It’s easy to think that charging and storing batteries inside a “fireproof” or “explosionproof” container is enough, but it usually isn’t. If you have a fire in one of these containers—even if it works as designed—you can expect a cloud of toxic smoke, the area around the container to be scorched, and lots of soot damage to the room. The BAT-SAFE aims to solve all of these problems.
There are many LiPo bags on the market that provide almost no protection whatsoever, and the good ones cost a lot of money. It’s a known fact that a LiPo bag can’t handle large batteries. What counts as large and how many is safe? It’s a dangerous guessing game to decide how much you can put in unless a product is rated. The BAT-SAFE has a rating of 222Wh. That works out to two 6S 5000mAh, ten 4S 1500mAh, or twenty 3S 1000mAh batteries. Figure out the Wh of a battery by taking its nominal voltage (3.7 per cell for a LiPo) and multiplying by amp hours (mAh divided by 1000). A 4S 1500mAh battery is 4 cells × 3.7V × 1.5Ah = 22.2Wh.
An ammo can may contain flames, but it will very rapidly transfer heat to the surface of the box. That heat may scorch anything nearby, and could even cause combustible materials to ignite. To contain heat, the BAT-SAFE has very thick, insulated double-walls. Each side of the box is roughly an inch thick! BAT-SAFE still warns of placing the box on a combustible surface.
Another major problem is smoke and soot. A LiPo fire dumps out lots of hazardous chemicals. Soot gets into almost everything it touches: walls, ceilings, carpets, furniture… anything that can absorb it will be ruined. Many ammo cans come sealed, but keeping the seal in place is a bad idea. A burning LiPo emits a lot of gas, which will build up considerable pressure in a sealed container and potentially cause it to explode. The solution to both of these from BAT-SAFE is a sealed lid with a filtered vent system. The vents allow these expanding gases to escape, and the filter removes much of the soot and harmful chemicals. BAT-SAFE doesn’t promise the vented gases are healthy to breathe, but it’s obvious that the filter considerably reduces the amount of gunk coming out—the smoke that does come out is white.
If you do have a fire, don’t open the box again unless the area is well ventilated. Whatever gas and soot the filter didn’t allow to escape will still be inside the box. You could get a face full of it when you break the seal. The BAT-SAFE literature warns of lingering carbon monoxide. Opening the box may supply additional oxygen, allowing batteries to re-ignite if there’s still enough lingering heat and fuel. If it’s a particularly large fire, it’s probably best to just not open it at all and get rid of the whole thing without breaking the seal.
The BAT-SAFE is fairly light weight at 1920g (4.2lbs). The exterior is 300 × 220 × 160mm (12 × 9 × 7in) and has an interior space of 240 × 165 × 80mm (9.5 × 6.5 × 4in)—That’s about 20% lighter than a typical ammo can, about an inch larger each way on the outside, with about half that space available inside. Everything about it feels well constructed: hinges are smooth and quiet, the latch lines up properly every time, bumpers prevent it from scratching other surfaces, and reminders on how to use it correctly are printed onto the box. The designers have obviously put a lot of thought into making the BAT-SAFE simple but effective. There were some minor scratches on the box lid with both of our test boxes, and insulation fibers do peek out here and there where the steel wall pieces meet. Neither of these hurt the functionality, so they certainly didn’t bother us. This isn’t a product you buy to show off.
The placement of vent holes in the lid was a deliberate choice. With the vents in the lid, you’ll need to keep them clear in order to get your batteries in and out of the box. It’s a constant reminder that covering the vents prevents the filter from working. Even some human psychology went into the design of the BAT-SAFE.
Another attribute that speaks to build quality is that the box may be reusable. If you store smaller batteries, a fire won’t get hot enough to damage the box. Mr. Mast states that with a fire of 3000mAh or below, you can typically just clean it out and it’s no worse for the wear except that the filter will smell of soot. Above 5000mAh, the heat is much more intense—it’s far more likely to damage the box so that it can’t be reused.
The box has a carrying handle on one side. The handle is partly elastic and part heavy strap. It stays more or less flush with the box when not in use, but doesn’t hurt your hand while carrying around like pure elastic would. The box is a little bit too large to really call “portable”, so you may not be carrying it out to the field when you fly, but keeping your batteries in it while transporting in the car is simple enough.
The graphic design and visual appeal is slightly less than you’d expect from a typical commercial product. The box is covered with the visual cliche of bat animals on every side, and the website feels a bit low-budget. After getting a look at the product itself, neither of these are an issue for me. It speaks to a product design focused on safety and functionality rather than marketing. I’m comfortable with that.
Setup and Usage
Using the BAT-SAFE does take a little bit of setup at first. You have to pull out the “wire way seal”, which is 2 matching pieces of silicone fed through a special hole in the box lid. You put your charge cables in between them and feed them back into the hole. This takes a bit of effort because the seal is supposed to close around the cables to prevent gas from escaping around them. The BAT-SAFE makes this procedure somewhat easier by including a pull tab on each piece of the seal.
When your wires are in place, you can connect your battery inside the box and your charger outside the box. You shouldn’t put your charger where it can cover the vents, so the box ships with a removable charger stand that you can attach to it. If you have a 4-button charger, this will sit nicely on the stand. Something larger like the SkyRC D100 doesn’t work nearly as well. I had to bend the provided angle bracket into a flat position to allow enough room for the D100 to sit on top, which provided just barely enough room to route the cables without going over a vent hole.
Users with even larger chargers like those with four channels will have to improvise; it’s clearly not designed with these in mind. Since my charger has two channels and I use temperature sensors, it’s a lot to fit through the wire way. It may not really work at all with four sets of cables running through—or at the least, it might not create a good seal, allowing gas and soot to escape instead of going through the filter.
You might need to extend your charge cables to run through the wire way, especially if you’re supposed to plug your balance lead directly into the charger or if you can’t use the stand to place your charger on top of the box. BAT-SAFE sells a pack of balance lead extenders for this purpose, which work well. If you need to extend your main charge cable, you’ll have to source your own. If you like to parallel charge, there’s generous enough space to set it up. Place the charge board inside the box and run your board cable through the wire way.
Once you’ve got it set up, using it is effortless. The only added steps to normal charging are to open the box to plug your battery in, then close and latch the lid before punching in the settings on your charger. BAT-SAFE’s developers wanted to create something so easy that it would get used every time, and they hit the nail on the head here. You’ll have absolutely no reason not to use it. It will be harder not to.
Does it Work?
According to BAT-SAFE, it’s the only product of its kind that’s reliable. Mr. Mast claims to have run dozens of tests ranging from medium to large batteries. In one test of the prototype, the box was completely surrounded by tissue paper. The paper never caught fire even though nothing inside the box was recognizable. Tom also claims that he has already received a big thank you from a customer that surely would have been facing a building fire without it.
While we don’t have any reason to doubt Tom, I couldn’t find a single review where the box was independently tested. We feel that reviews should do more than restate the marketing materials, and actually verify if a product works as advertised. We had the opportunity to conduct a controlled test of our own and find out whether it really worked. In short, the box performed extremely well. It completely contained the flame of our 15-battery burn while its surface temperature rose only about 10 degrees. We weren’t able to examine the filtered smoke to see how much soot it still contained, but the amount of smoke the escaped at all was far less than from much smaller tests in other containers. The performance is truly impressive.
Think about your batteries right now. If something were to happen, would there be fire or heat damage? Would anyone breathe in hazardous gas? Would black soot destroy your walls, ceilings, or other possessions? If you can’t confidently answer “no”, you may want to rethink how you are handling them. If you trust your DIY skills, there are a few tutorials on how to create safe boxes, like this one from VAS, or this page on Flite Test. Proper use of these DIY builds, LiPo safe bags, or ammo cans should contain flames. Some of these will contain the heat. None will contain the gas and soot. What are you putting at risk?
We can confidently say the BAT-SAFE is the highest performing product we have seen in this category. Everything about it seems well-built and designed to make sure you use safe handling procedures with your batteries. In our live fire testing, it handily outperformed the LiPo Safe bag and ammunition box for flame, heat, and smoke containment. Other containers may provide adequate protection in your shed or garage, but the BAT-SAFE is the only container we would recommend if you must charge inside your home. You can get more information or order yours at bat-safe.com.