Now that it is clear that all 2.5 million Samsung Galaxy Note 7 devices that have been sold thus far are at risk of exploding the question remains why exactly are they at risk? So far we have not officially heard from Samsung regarding the findings of their investigation. We have only heard that there have been 35 confirmed reports of Note 7 devices catching fire or exploding. Samsung has acknowledged that defective batteries are to blame. Samsung has even announced they will no longer be using batteries provided by their sister company SDI who produced 70% of the batteries used in Note 7 devices. What is wrong with the SDI batteries? Cell phone batteries have several regulators and fail safes built in to protect the battery from overcharging, expanding, overheating, and exploding. The charger is the first step in the line of protection. Using a third party charger can damage the internal circuitry. The charge port is the next layer of protection. It should automatically detect inadequate chargers and regulate the electrical flow accordingly. If these two layers fail their is a third layer of protection built into the battery itself. In the Note 7 there is a protection circuit board attached to the top of the battery. The built in circuit board regulates voltage and temperature ensuring the battery itself does not overcharge. The board includes a fuse which should blow if the phone gets too hot stopping the flow of current and prohibiting your phone from exploding. If you examine a photo of a Note 7 which has exploded you can see which of these fail safes has failed. In the photos you see there is no burning or scorching near the charge port, or even where that port connects to the motherboard. Their is also no scorching where the battery plugs into the main board. The main scorching and burning is found where the battery sits. Zack from Jerry Rig Everything has actually done a full battery tear down which I'll link to below. He explains that due to the burn marks we can see on the phone it looks like the battery shorts out which causes the explosion. This is likely due to a faulty battery circuit board since this is happening during charging. The good news is that while you wait on your recall as long as you don't charge your battery you should be fine. The phone shouldn't randomly explode.