Samsung's exploding batteries

GopherT

Joined Nov 23, 2012
8,012
How is this possible?:

http://www.nbcnews.com/tech/tech-news/samsung-galaxy-note-7-batteries-reportedly-catch-fire-n641066
  • Does the fault lay in the batteries themselves?
  • In the way power is being drained from them?
  • In the way they're being charged?
This is a serious setback for Samsung
Batteries over heat because of internal resistance x current draw.
- It is completely possible that some combination peripherals draw more current than the battery can handle when activated simultaneously (or designers were not expecting that all phone peripherals are activated at the same time. This is a difficult fix if they want all phone functions to be possible (must find a battery with lower internal resistance, or battery with higher temp capabilities before packaging materials break down).
- they can use software to limit which peripherals are active at a given time (unfortunate because marketing people likely advertised multitasking or something that contradicts limitations).
- if fires occur on charging only, they need to re-program or alter the charging circuit (hopefully this is the issue - it could be that an incorrect current sensing resistor was selected or a resistor with too broad of tolerance was selected (or even a bad batch of resistors were used). I think they are hoping this is the issue).
 

OBW0549

Joined Mar 2, 2015
3,566
How is this possible?
In addition to the above, it's also possible that something, perhaps an assembly error or mechanical clearance problem, caused the battery to be shorted out. Some lithium batteries are capable of delivering absolutely enormous currents when it is demanded of them, far beyond safe limits.

35 years or so ago at a company where I worked, a circuit board containing a real-time clock chip and a lithium backup battery went into production. The battery was an axial-lead part about the size of a standard "C" cell; I forget what milliamp-hour capacity it was rated for, but it was a real brute.

All went well until it was time to solder the first production run of boards.

Back then, all components were through-hole, and production soldering was done on a wave-solder machine. Unfortunately, Murphy's Law invoked itself: the backup battery was oriented on the circuit board in a direction such that when the board passed over the solder fountain, both leads of the battery would contact the liquid solder simultaneously. The result was spectacular: BANG!!!!!!!

The wave machine operator had the messy task of cleaning lithium battery shrapnel out of the wave machine; he was NOT pleased.
 

MrSoftware

Joined Oct 29, 2013
2,012
There have been at least a few other device models that had battery fires. I think it was Sony or Dell that had a laptop model that caught fire. From memory, the problem was metal particles that got into the lithium batteries somehow during manufacturing. I'm likely forgetting some key details, but I think the batteries were shorting internally somehow and then catching fire from the heat.
 

ian field

Joined Oct 27, 2012
6,539
There have been at least a few other device models that had battery fires. I think it was Sony or Dell that had a laptop model that caught fire. From memory, the problem was metal particles that got into the lithium batteries somehow during manufacturing. I'm likely forgetting some key details, but I think the batteries were shorting internally somehow and then catching fire from the heat.
AFAIK: Sony is one of Dell's suppliers.

Even Boeing have had an embarrassing moment with lithium batteries.
 
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