The above image was created using AI.
There are three things you need to know about electric vehicles. One, keep them away from sunlight. Two, never get them wet. And three, don’t feed them after midnight.
Oh wait, that’s Gremlins. EVs love solar power, and are cheaper to charge from the wall socket after midnight, and—well, okay, you’re not supposed to get them submerged, like any other road vehicle. But do they actually explode when you dunk them in water?
The recent fatal ferry fire has led a lot of people to think so, but the investigation into that fire has not yet concluded. From what little information is available, the blaze started with an explosion, which could also have been caused by fuel vapor leaks from a gasoline-powered vehicle in the compartment or from a leaking gas line in the ship itself. Statistically speaking, EVs are some twenty times less likely to catch fire than gasoline cars, even when comparing the same make and model with both options available.
No matter how the fire started, exposing a lithium battery to fire is no joke. When it gets hot enough, at about 150 degrees, a thermal runaway starts, and the battery, being able to supply both fuel and oxygen at the same time, can burn at up to 1,000 degrees.
Not coincidentally, this is the same temperature at which gasoline burns. The key difference is that lithium is self-fueling. With the nickel-manganese-cobalt chemistry in certain long-range EVs, the extreme heat separates oxygen from the metal oxides in the electrodes, which then reacts with the lithium and feeds the flames.
With the lithium-phosphate batteries in mass-market EVs such as your common BYD, however, the oxygen is bound more strongly. This means greater thermal stability, which means batteries don’t tend to explode if overcharged, and autoignition doesn’t occur until 270 degrees Celsius—about the same as gasoline. And even then, you don’t get the massive release of oxygen you do from other lithium types. There have been fires involving lithium-phosphate vehicles in which the main battery pack has survived remarkably intact.
Mind you, there is still a risk of explosion from outgassing, but a pack has to be heavily damaged for this to happen. In the real world, barring a catastrophic collision, these batteries don’t tend to burn unless they are directly exposed to fire or submerged in water.
And yes, while water intrusion is bad for EV batteries, manufacturers build their batteries with this in mind. EV batteries are usually watertight. Even if you dunk the car in water, it’s very unlikely for water to penetrate the battery, as examinations of flooded EVs have shown.
Some commenters have brought up rough seas and damage while loading as a possible cause of thermal runaway. While it is possible to damage an NMC battery and cause such a situation, you still need to puncture the battery case and compromise the internal structure to cause an electrical short. This will take much, much more force than simply scraping against the edge of a loading ramp.
Saltwater-laden air is often brought up as a risk. But just about every EV sold here is transported by sea. Temporary exposure to salty air will not harm the vehicle in the long term. And inside the hold, you have even less exposure to worry about. Now, having the vehicle actually sit in saltwater for long periods of time can cause the type of corrosion that leads to fires. But corrosion is long-term damage, and the effects often come in the days or weeks after severe flood damage.
Instead, what makes EV fires scary is that these very strong, very well-insulated battery housings make it nearly impossible to get water into the battery itself once it’s on fire and a thermal runaway starts, the fire feeding itself out of the reach of outside CO2 or water suppression.
So yes, once those batteries catch fire, it can be very scary indeed. But for an EV battery to get to that point requires a catastrophic failure of the fire-fighting equipment on board the ferry in question.
And again, if the batteries are lithium-phosphate, they won’t catch fire until the fire they’re exposed to is at a very high temperature. And even then, they don’t pose the same level of thermal runaway risk that NMC packs do.
This is not to say the risk is zero. There is always risk. Like there is a risk when loading any type of motorized vehicle on a cargo carrier. For long-distance sea transport, most fuel-fed vehicles are transported with only a small amount of fuel, to minimize risk. We cannot, obviously, do the same with EVs, but local inter-island ferries don’t make gasoline or diesel vehicles unload their bladders before each trip, either.
Thousands of EVs enter the Philippines every year via sea, and this is the first time we’ve had any kind of maritime fire possibly linked to an electric vehicle. There have been four major maritime fires in the Philippines in the last five years, mostly linked to shipboard engine or electrical system issues.
This is why the Maritime Industry Authority (MARINA) says it is still investigating the cause of the fire. There is a precedent for explosions—such as the one reported here—occurring due to poor ship maintenance. The gas buildup required for an explosion requires a long-term leak in an enclosed space—usually the engine room. To produce enough gas to cause an explosion in a much larger cargo hold would be a difficult task for a single electric vehicle to achieve in the half-day the ferry was in transit. And if the vehicle used a lithium-phosphate battery, the hydrogen gas produced would tend to rise and escape into the atmosphere.
We cannot deny that NMC packs are still a risk—if they catch fire—but knee-jerk bans on electrified vehicles of all battery sizes and types is simply feeding into the hysteria. Hybrids, which some carriers are now also banning, have tiny 0.9-1.7kWh battery packs. That’s a tiny fraction of the size of the packs on full EVs, and pose no more risk than a full tank of gasoline. Which, again, these shipping lines don’t require you to dump overboard before the trip, either. And hybrid batteries are usually carried higher in the vehicle frame, inside the passenger cell, where they’re not exposed to mechanical damage or corrosion from outside sources.
In the end, you cannot compel a private company to accept a risk it is not willing to take, however unlikely. One wishes, though, that the response would be more proportionate to the risk. And some carriers are still accepting EVs without issue. Modern fire suppression methods, along with safer lithium-phosphate batteries, keep the risk down to the same level as fuel-powered vehicles. But it will be up to the government to strengthen fire safety inspections and to come up with more comprehensive standards and policies regarding EV transport risk and safety to prevent any possible incidents in the future.