It was just four high-energy batteries, the kind that are found in a lot of military equipment such as walkie-talkie sets and night vision equipment. Similar batteries already were being used on the international space station. But when NASA officials discovered last year that Russian space officials were allowing the four batteries on-board the space station without the proper testing, they objected strenuously. The batteries could be toxic and had a small potential to explode. The Russians went ahead anyway.