I suppose this (assuming it was the batteries again. I understand they swapped them out with a new design) is the downside to making a system fail safe instead of making it just not fail. They modified the battery compartments so that a fire wouldn't threaten the air-worthiness of the aircraft but any fire is still likely to cause bad press and, in this case, disrupt traffic at an airport.

Fire doesn't look like it's near the batteries.

Maybe they should have taken Elon up on his offer...

The question in my mind is far more fundamental than anything related to the design of the battery packs or whether or not Elon Musk's involvement is of any real engineering value.

None of that matters. He/they would have to convince me that LiPo/LiIon packs are safe. This coming from someone who's waiting for Tesla's SUV's. I kind of draw a demarcation line between flight and road-based vehicles. Fires are a thousand times more dangerous at 30,000 feet.

The fundamental issue I keep coming back to is that Lithium Polymer batteries are dangerous. One or multiple cells. It does not matter.

I've been using and abusing them extensively for, I don't know, maybe a decade, in all of my RC gliders and helicopters. I keep them locked-up in a fireproof container and never --ever-- charge them unless I can be in the room during charging.

There are plenty of accounts in RC circles of battery packs spontaneously combusting, catching fire in flight, catching fire while charging or lighting-up if damaged. The problem, as it was explained to me, is that these cells can produce methane and have an avalanche failure mode. Methane is a product of a manufacturing defect whereby a small amount of moisture is sealed into the package. Lithium reacts unfavorably with moisture and the rest is history.

Lithium Polymer battery fires are extremely hot, fast and very powerful. I've seen it myself with three and six cell packs. I would not want to be anywhere near a fire in a larger pack.

And so the fundamental question for me is simple: Why? Why use Lithium-based chemistry for a flight battery pack. Yes, I know, lower weight, lower volume. However, I am not sure these packs can ever be considered to be safe. How can an aircraft manufacturer ensure that the quality of the packs it assembles is as required? Can you ever know?

I know millions of Lithium-based batteries are in use in everything from phones to laptops and more. Not sure how to think about that. A fire is a fire. A laptop stowed away in cargo can still cause a huge problem if it catches fire.

To be fair, I have never had a spontaneous fire in any of my thirty of forty packs (ranging from 2 cells to 12 cells). I have had cells spontaneously puff-up --inflating like a baloon-- and destroy the pack by expanding so much that the battery pack's casing cracks open. In those cases I've used them to experiment by overcharging to see how they light up. It does take a lot, but when they do it is massive fireball.

Perhaps someone with information closer to the source or quantifiable safety and reliability data can pitch in?

EDIT: Prior to LiPo's I was using NiCd (Nickel Cadmium) cells and have never had any issues, even with abuse and mechanical damage.

Sounds like Boeing should have taken Elon Musk up on his offer to help out with the lithium battery design.

I wonder how Airbus pulled this off?

peeks from under tinfoil hat