The OLPC XO BTest-3 will have a new battery based on LiFePO4 chemistry. LiFePO4 was a battery technology proposed by researchers at the University of Texas and revisited by other companies (there's evidently some patent disputes around the technology).
The LiFePO4 battery promises to be safer, less at risk for explosions, and colder running batteries. Lithium iron phosphate is an intrinsically safer cathode material than LiCoO2. The traditional downside of this has been lower voltage and less energy density. It's good that OLPC is moving towards battery technology that aims at higher safety (and lower toxicity to boot) -- can you imagine one battery recall per child?
Before you worry about under powering the computer, the new OLPC XO chipset, an AMD Geode LX-700 433Mhz .13 micron chip sipping an impressive 0.8 watts, will allow Python, the primary programming language in the OLPC, to run 2-3 times faster, and can potentially double the camera frame per seconds to 30.
These upgrades aren't free, of course (no word on exactly how much this will up the cost), but they dramatically expand the power of the OLPC XO, and gives it some on-board cryptographic capabilities. It's a delicate balancing act between dramatic increases in power, utility, and safety and raising an already over-budget cost on the other.