The BajaSAE Rules do not currently limit batteries based on their chemical makeup. The rules DO state that the battery be must be sealed and non-spillable.
Therefore, those common types allowed are (but are not limited to the following):
Sealed Lead-Acid (SLA)
Absorbed Glass Mat (AGM)
Nickel-Metal Hydride (NiMh)
Dry-cell batteries (standard A, AA, AAA, C, D, 9V, Lantern, etc.)
In addition, the rules do not state this explicity; however, all batteries used must be manufactured and obtained commercially. That is, teams should not attempt to fabricate their own custom battery or battery cells, and batteries whose inner makeup appears to be "home made" will not be permitted due to construction-quality and safety concerns.