You might have heard that the Samsung Note 7 had some igniting / exploding issues. Since then, the phablet has been pulled and Sammy wrote a nice letter to say sorry. Now, engineers over at Instrumental Technologies have revealed exactly why the phone’s battery exploded.

The clever folk over at Instrumental have performed a thorough investigation of the Samsung Galaxy Note 7 to find out why it went boom.

Unfortunately, the reason wasn’t that it was just too full of awesome. It seems that the issue was quite a bit more mundane.

What caused the Note 7 to fail?

The short answer is that the Samsung Galaxy Note 7 failed due to improper tolerances.

When designing and building anything, engineers should always take in to consideration a range of tolerances. These will allow for any changes to the product due to external or internal forces. These can be environmental (cold / hot weather, rain, etc) or physical pressures (bending, stretching, etc).

Most designs will allow for a certain amount of deviation. In the Note 7’s case it seems that the space between components was the crucial factor.

Hot stuff

Traditionally, when the dimensions of a component move beyond a certain tolerance when they are under thermal loads (become too big when they are hot, let’s say), they are rejected or marked as non-compliant.

In the case of the Samsung Galaxy Note 7, the battery was situated in a phone with very tight tolerances. Consumers want longer battery life but in a thinner device, right?

This means that the battery in the Note 7 came as close as 0.1mm to the rest of the phone. Even in the ‘larger’ spaces, it was never further than 0.5mm from the edge of the batteries CNC-machined battery pocket.

No wriggle room

All this extreme engineering meant there wasn’t the room to allow for parts to expand when the phone was placed under load.

These parts, naturally, included the battery.

This all added up to the phone exerting pressure on the battery, allowing the battery’s positive cell layer and negative cell layer to be squeezed closely together.

When this happens the insulation material between these two layers becomes useless. Energy could then be fed from one layer to the other. This causes a ramp up in temperatures and a huge fire-risk.

Samsung used a 3,500mAh battery in the Note 7 to give it a competitive battery life. It is thought that this would have lead to failure even if the ‘explosion issues’ didn’t occur. Over time the battery in the phone would have expanded, resulting in a phone which would have warped and changed its shape as a result. So, in either case, it would have been a negative outcome for Galaxy Note 7 users.

The end result

The failure of the Samsung Galaxy Note 7 is due to Samsung placing a large battery into a compact space.

For something that is innovative and new, you design the best tests that you can think of, and validate that the design is okay through that testing.

Instrumental Technologies states that the Samsung Galaxy Note 7 would need to use a battery that was smaller than both the Galaxy Note 5 and iPhone 7 Plus to be safe for use.

That would have made the devices’ battery life short and not competitive in the modern marketplace.

In the eyes of the engineers at Instrumental Technologies, the design of the Note 7 has “no competitive salvageable design”, effectively making the phones design a dead weight for Samsung.