It was battery two in the LEM which had four batteries, each one designed to compensate for loss of power in any of the others. The damaged battery was still working despite the small explosion.
The astronauts were still wearing their bio-medical sensors. Lovell pulled his off because they were becoming uncomfortable and to conserve power. When the Capcom found out he just said “OK”.
Houston wanted Odyssey to be powered up because the systems were sensitive to the cold. Capcom told Lovell that the explosion was a minor one in battery two in the LEM and that a burn for realignment of the re-entry angle was required.
Meanwhile the crew were beginning to experience health problems and had decided to drink as little as possible when the capsule began to become cluttered with bags of urine. Venting helium was eroding the re-entry angle.
Lovell regarded both his crewmates and reflected on what he ought to do next, but before he could reach any conclusions, his thoughts were interrupted. From beneath the floor came a dull pop, then a hiss, then another thump and vibration ratted through the cabin. Lovell leapt forward toward his window. Below the cluster of thrusters to the left of his field of vision, he could see a far too familiar cloud of icy crystals floating upward. For an instant Lovell was startled, and then just as quickly he knew what the sound and the vent were.
“That,” he said, turning to his crewmates, “was the end of our helium problem.”
They re-established the PTC roll.
At 8 pm on Thursday, 16 April the re-entry angle was beginning to decay again. The Atomic Energy Commission was concerned about a fuel rod in the LEM which should have been left behind on the moon, in the descent stage. Although the LEM would be jettisoned in space it would eventually fall to earth, so the Atomic Energy Commission wanted to ensure that it fell into the deepest water possible.
The food supplies in Odyssey had frozen solid. They had to decide the best way to handle the separation of Odyssey and Aquarius.
When the time came to jettison the service module, they decided Jim Lovell and Fred Haise would stay in the LEM, while Jack Swigert would scramble up into the command module. Moments before separation, Lovell would fire the LEM’s thrusters for a single pulse, pushing the whole spacecraft stack forward. Swigert would then press the button that fired the service module’s pyrotechnic bolts, cutting the huge, useless portion of the ship loose. As soon as he did, Lovell would light his thrusters again, this time in the opposite direction, backing the LEM and its attached command module – with Swigert aboard – away from the drifting service module.