Car Battery

Car Battery is a passive item added in Afterbirth.

Effects

 * Causes Isaac's activated item to activate twice on each use.

Synergies

 * Blank Card/Placebo: Activates the card or pill twice.
 * Blank Card + Algiz: Doubles the shield duration to 60 seconds.
 * Book of Revelations/Satanic Bible: Isaac gains 2 soul/black hearts.
 * Book of Shadows: Active shield lasts for 20 seconds as opposed to 10 seconds.
 * Box Of Friends: Adds two of each unique familiar.
 * Crooked Penny: Gives a 25% chance to quadrouple all items and consumables.
 * Deck of Cards / Mom's Bottle Of Pills: Spawns two pills or cards. The second pill or card is dropped on the floor unless Isaac has Deep Pockets, Little Baggy, or Starter Deck.
 * Glass Cannon: Fires two tears.
 * Guppy's Head: Doubles the amount of flies spawned.
 * Head Of Krampus: Fires two sets of Brimstone beams, each of which has a chance to rotate.
 * Monster Manual: Spawns two random familiars. May spawn the same familiar twice.
 * Prayer Card: Gives an instant heart container.
 * Tammy's Head: Doubles amount of tears fired.
 * The Gamekid: Increases the duration of the Gamekid effect.
 * The Pinking Shears: Spawns 2 headless bodies.
 * Unicorn Stump: Increases the duration of invulnerability.
 * Yum Heart: Replenishes two red hearts instead of one.
 * Wooden Nickel: Increases chance of spawning a coin, and adds possibility of dropping two.

Interactions

 * ? Card: Only activates the item once.
 * Book of Secrets: Activates twice, but has a chance to uselessly activate the same effect twice.
 * D6, D8, D12, D20: Re-rolls twice instantly without any benefits.
 * D4, D100: Instantly re-rolls Isaac's items twice, which doubles the speed at which the item pools are exhausted and transformations are achieved.
 * Dead Sea Scrolls: Activates 2 random effects.
 * Guppy's Paw: No effect.
 * IV Bag: No effect.
 * Jar of Flies: No effect.
 * Kamikaze!: Doubles wait time between uses without any benefits.
 * Pandora's Box: No effect.
 * The Book of Belial: No effect.
 * Razor Blade: No effect on hearts depleted, nor on damage gained.
 * Red Candle: No effect.
 * Diplopia: A second car battery has no effect.
 * Ventricle Razor: Places both trapdoors in same location.

Seeds
A188 W1Q8 (First floor shop)

Car Battery