"We don't want to scare anybody, because there is a huge market out there; but we have had problems with batteries, and in many instances, the chargers," said Scott Wolfson, spokesman for the U.S. Consumer Products Safety Commission.
Cell phone safety experts say it's generally best to use batteries recommended by the handset maker. Look for a "UL" logo on any battery you use. That certifies that the device has passed industry-standard lithium battery safety tests.
Cell phone explosions on rise 
danger of fake batteries.
Many incidents have involved unapproved products and counterfeits that can be identified with some rudimentary knowledge.
Manufacturers such as market leader Nokia now publish guides to assist consumers in identifying fraudulent products. A Nokia primer on counterfeit batteries includes photos of fake goods, with well-marked explanations that point out identifying features.
Misspelled words, "Made In China" stickers and unevenly printed or crookedly applied labels are all surefire signs of a counterfeit, Nokia warns.
Even genuine products are not immune to failure. Before buying a replacement battery, or a spare, check with consumer protection agencies such as the Consumer Products Safety Commission for information on recalls, wireless-product safety experts suggest.
Other safety tips include:
• Never use a cell phone that's very hot to the touch or bulging. Overheating batteries typically vent hot gases that can cause serious injuries, so keep your distance.
• Unplug a charging phone immediately if there are signs that the phone or battery is overheating. Notify the manufacturer before using the phone again.
• Avoid using chargers and batteries made by different companies, and don't buy batteries that have signs of damage, such as scrapes or dents.
