Active items will activate their effects 4-6 times when used, with a 50% chance for the held active item to disappear afterwards.
Notes
Some active items that are otherwise listed as ineligible for Car Battery may have Eternal Car Battery attempt to duplicate their effects; despite this, some items may still not be able to be effectively duplicated by Eternal Car Battery.
Eternal Car Battery does not apply its effects to active items in the player's pocket slot, and will not remove them when used.
Car Battery: Active items will be activated 5-7 times, if they would be eligible with Car Battery. If not, then they will be activated 4-6 times as usual.
Azurite Spindown: If Azurite Spindown is used to reroll Eternal Car Battery, it will be rerolled into Angry Faic.
How to Jump: Results in a very unusual interaction — Isaac instantaneously going out of bounds briefly, usually reappearing in a corner of the room. This can inadvertently cause Isaac to become soft-locked in some room layouts.
IV Bag: As it's used multiple times at once, it will take multiple hearts from Isaac's health bar and drop multiple coins in return. This can be quite dangerous, as it will likely kill Isaac if he doesn't have enough health.
Pandora's Box: Drops additional rewards that are based on the current floor when used.
Pandora's Box + Strange Key: Will only pay out with the 6 collectibles once, the additional rewards created will be those based on the current floor.
Forget Me Now: Returns Isaac to the beginning of the run in Chapter 1, effectively acting as if Isaac had used R Key.
Diplopia: On use, duplicates all items and pickups in the room one additional time, instead of 4-6 times. The duplication will stack exponentially rather than multiplicatively, however, resulting in creating 3 copies of each item and pickup.
However, there is still a 1/100 chance it will duplicate all items and pickups an additional time, which it will roll for 3 times; resulting in creating 7 copies, 15 copies, or 31 copies of all items and pickups in the room.
Eden's Soul: Will spawn 6, 8, 10, or 12 collectibles from the current room's item pool when used.
Void: Does not grant additional stat boosts for consuming passive items. Active items that have been absorbed by Void will be affected by Eternal Car Battery when Void is used.
Eraser: Immediately erases all enemies in the room the moment Eraser is used, even before Isaac throws it.
As a result, it's possible to use Eraser multiple times per floor if Isaac does not throw it, (which would otherwise consume the charge,) and if it does not get removed by Eternal Car Battery.
This effect will not erase bosses or mini-bosses, regardless of if they are under 15 HP.
Car Battery may have Eternal Car Battery attempt to duplicate their effects; despite this, some items may still not be able to be effectively duplicated by Eternal Car Battery.
Trinket Multipliers: No effect.
Azurite Spindown: If Azurite Spindown is used to reroll Eternal Car Battery, it will be rerolled into 
Angry Faic.
How to Jump: Results in a very unusual interaction — Isaac instantaneously going out of bounds briefly, usually reappearing in a corner of the room. This can inadvertently cause Isaac to become soft-locked in some room layouts.
IV Bag: As it's used multiple times at once, it will take multiple hearts from Isaac's health bar and drop multiple coins in return. This can be quite dangerous, as it will likely kill Isaac if he doesn't have enough health.
Pandora's Box: Drops additional rewards that are based on the current floor when used.
Strange Key: Will only pay out with the 6 collectibles once, the additional rewards created will be those based on the current floor.
Forget Me Now: Returns Isaac to the beginning of the run in Chapter 1, effectively acting as if Isaac had used 
R Key.
Diplopia: On use, duplicates all items and pickups in the room one additional time, instead of 4-6 times. The duplication will stack exponentially rather than multiplicatively, however, resulting in creating 3 copies of each item and pickup.
Eden's Soul: Will spawn 6, 8, 10, or 12 collectibles from the current room's item pool when used.
Void: Does not grant additional stat boosts for consuming passive items. Active items that have been absorbed by Void will be affected by Eternal Car Battery when Void is used.
Eraser: Immediately erases all enemies in the room the moment Eraser is used, even before Isaac throws it.
Mystery Gift / 
Mama Mega! / 
Genesis / 
Esau Jr. / 
Damocles / 
Empty Book / 
Eternal D12 / 
Dusty D10: Blacklisted by Eternal Car Battery — will not activate multiple times, nor can they be removed by Eternal Car Battery.
Eternal D6, including its similar effect of having a chance to remove items.
