The heat played a role, causing the Sunseeker car's batteries to overheat. As WMU News reported:
The WMU team was in first place from roughly noon to around 2:30 p.m. Saturday, the final day of the race, when battery temperature was too high to continue without cooling. The surface temperature of the track was reported to be a blistering 139 degrees as thermometers recorded the highest temperatures seen in Texas so far this year.
To read more, please follow the links below:
WMU NEWS — WMU team finished fifth in Formula Sun Grand Prix solar car race
MyWMU — Formula Sun Grand Prix 2013