- "That's a battery. That holds magical current."
- ―Julia Wicker
A Magical Battery is a repository created from living metal to store magical energy.
- "Magic is dead."
"No, it's not, and you proved that today, right? With Mayakovsky's Battery."
"It's not his. It's mine."
"Of course, it is. Of course, it is."
"Do you think that he could make this without me? Where do you think he got the living metal in Antarctica? Me. Me. Everything he asked for, I gave him everything."
- ―Eleanor Lipson and Quentin Coldwater
Following his banishment to Brakebills South, Mischa Mayakovsky began working on several projects meant to help him escape the Incorporate Bond placed on him. In 2016, he realized that the levels of magic in the universe were dropping at an alarming rate, and devised a plan to prepare for magic's disappearance. Using a supply of living metal given to him by Professor Lipson, Mayakovsky began dismantling all of the equipment used in Brakebills South with magic, releasing their energy to be stored in the enchanted metal.
After retrieving the shade of Alice Quinn from the Underworld, Julia Wicker and Quentin Coldwater traveled to Brakebills South to ask for Mayakovsky's help in restoring Quinn to a human. Mayakovsky stated that the act of restoring a Niffin to life was possible, but they would need more power. At that moment, Wicker noticed a battery in Mayakovsky's office and stated it was the largest one she'd seen, suggesting that they use his batteries to power the spell, but Mayakovsky told them he didn't have enough to spare for the spell. Coldwater reminded Mayakovsky that his involvement with Emily Greenstreet is what got Charlie Quinn killed and put Alice on the path to becoming a Niffin, explaining that he was entirely responsible for Alice's condition and was obligated to help them save her. Mayakovsky then relented, helping Coldwater and Wicker combine Quinn's Shade to her body and restoring her to life again.
After the Old Gods sent the Plumber to shut off access to the Wellspring, the incorporate bond placed on Mayakovsky was lifted and the Master Magician fled from Antarctica and got in contact with Emily Greenstreet, who he married soon afterward. However, the two were discovered by Lipson, who stole one of Mayakovsky's batteries before leaving. Lipson later used the battery to perform miracles for others, mourning the loss of magic in her life. When she was cornered by Quentin Coldwater on the roof of a building, Lipson attempted to commit suicide but was saved by Coldwater. However, she dropped the battery in the struggle and Alice Quinn was unable to catch it before it shattered and released its energy.
When Coldwater and his friends realized that Mayakovsky made more than one battery, they went back to Greenstreet's apartment but discovered that Kady Orloff-Diaz had already arrived and stolen the battery to save Penny Adiyodi's life. Julia Wicker traveled to meet Diaz in the Physical Kids' Cottage at Brakebills University, where the two used the remaining power in the battery to summon the demon Asteroth to save Adiyodi.
John Gaines' Sacrifice
After John Gaines learned that Reynard the Fox killed his wife, he traveled to the Physical Kids' Cottage, where he made Kady Orloff-Diaz perform a ritual to transfer his power into a battery to power a spell meant to kill Reynard. Julia Wicker used a spell from Ars Deicidium to charge a bullet with Gaine's energy, but was stopped by Persephone before she could shoot the trickster god.
As part of his deal with the Order of the Library of the Neitherlands, Henry Fogg created a battery could function without losing its charge to power a glamour he placed on Quentin Coldwater, Julia Wicker, Margo Hanson, Josh Hoberman, Penny Adiyodi, and Eliot Waugh to protect his students from Irene McAllistair after they successfully reactivated the Wellspring and exposed her and the Order's crimes against Fairies. When Julia Wicker, under the identity of Kimber D'Antoni, was accepted into Brakebills University, she was able to locate and disable the Perpetual Battery and drop the glamour placed over her and her friends.
After the Order used the Siphon to control the levels of magic in the universe, they issued out small batteries in the shape of coins to Magicians trusted by the Library. The coins were printed with the image of famous Librarians on them, but eventually became known as Deweys. The McAllistair Family, in particular, were given unlimited access to their batteries after the Order created a story of how their family saved all of magic in order to hide their involvement with Fairies.