Flaming Cellphones

phorm writes "Many of us have heard the urban legend of cellphones causing fires at the gas pump, but how about the hazards of replacement batteries? Reuters is carrying a story about a woman whose cellphone burst into flame, causing her superficial burn injuries. According to Nokia, the problem has occured before, and is related to non-brand replacement batteries. For various reasons, these batteries may overheat and catch fire, or even explode! So far I haven't found much info on whether this has happened with other brands of phone, though I do know that my little flip-phone gets very hot when running in analog mode. Perhaps some slashdot readers have had a similar experience?"

Comments

Other brands of phone - Siemens

[Animaether]

From a Dutch article*

A spokeswoman for Siemens said a GSM (cellphone) of the Siemens brand exploded last year in Germany. It concerned a phone that was placed in a carkit. During recharging, the phone had overheated and exploded. Nobody was injured in that incident. The user of the phone had bought the battery at a fleamarket.

* http://nu.nl/news.jsp?n=193292&c=51

Full power!

[ChilyWily]

So far I haven't found much info on whether this has happened with other brands of phone, though I do know that my little flip-phone gets very hot when running in analog mode. Perhaps some slashdot readers have had a similar experience?

Yup, analog transmits its signals at full power compared to other technologies like CDMA which dynamically adjust their power based on various factors (such as the signal to noise ratio, signal strength, how other cellphones in the same area are transmitting etc). More power for the signal requires a faster rate of discharge which translates into a more rapid chemical reaction that produces the heat in the battery. The issue with non-standard batteries (especially the cheap ones) is that they're not rated for the peak power consumption of the 'brand' phones - thus when the phone demands a surge of power for an extended period this stuff is likely to happen.

Lithium Ion batteries and overcurrent protection

[freshfromthevat]

Many LiOn batteries include built in gas gauging and over current protection. This costs about $1 in parts. Dallas makes some of the gas gauging parts -- DS2438 for instance. The gas gauging component is connected to the telephone via a 1 wire + ground interface. The overcurrent protection circuit is entirely internal. If the clone vendor wanted to save several nickels they could leave out the overcurrent chip and nobody would be the wiser until the battery shorts out.
The reason the overcurrent protection is built in is because Lithium Ion batteries will reach the flash temperature of plastic if current is drawn from them too fast.
So... don't rip the plastic off the pack and short them out except by remote control.
Thankyou.