The University of Nevada, Reno

Nevada Student Satellite Program

This program is generously supported by the Nevada Space Grant Consortium

Energizer Lithium Battery Data (provided by Energizer)

The NXT takes 6 AA batteries.
Energizer Lithium AA batteries (product type name L91) have an operating temperature range of -40 degrees F to 140 F.  One battery weighs 14.5 g (.5 oz), which is 33% lighter than an alkaline AA (product type name E91).  Our Lithium batteries also have a leak-resistant construction, no need to worry about a corroded battery.
Here are two links to the Energizer data sheets for L91 and E91 (for comparison):
Energizer Lithium:
Energizer MAX (alkaline):
The Energizer Lithium batteries, as you may be aware, are the longest lasting AA or AAA batteries in the market place and are designed especially for high-tech devices which have high drainage rates.  We have some testing results specific to the LEGO NXT that I'd like to share (testing results from 2006).  In summary, under continuous usage of the NXT, the performance advantage of Energizer Lithium batteries over alkaline AA batteries is 2-3.5 hours (the range depends on whether Energizer or LEGO testing protocol is followed):
Energizer Testing protocol (continuous usage): 
- Energizer Lithium lasts up to 7.75 hours vs. up to 4.25 hours with alkaline
LEGO Testing protocol (continuous usage):
2 motors - Energizer Lithium lasts up to 9.90 hours vs. up to 7.05 hours with alkaline
3 motors - Energizer Lithium lasts up to 8.10 hours vs. up to 5.60 hours with alkaline