Only has a chance to appear from battery drops in Hard mode.
0.83%
Cursed Battery
Varies (See description)
At random, either recharges Isaac's active item for up to 12 pips of charge, or deduct up to 6 pips.
This is capable of either overcharging Isaac's active item, or adding negative charges; a negative charge increases the amount of recharging needed before an item can be used, with every 1 pip recharged removing 1 negative charge from the active item, towards zero.
0.83%
Firework Battery
+6
After being picked up, the next time Isaac uses their active item, it will also activate the effect of Excelsior.
0.83%
Virtuous Battery
+6
After being picked up, the next time Isaac uses their active item, it will also activate the effect of Book of Virtues twice.
If multiple Virtuous Batteries are obtained, then the amount of times the Book of Virtues item effect is invoked will be increased.
0.83%
Storage Batteries
Storage Batteries are unique batteries that can be held in the same slot as cards, pills, and runes, being considered as objects.
Name
Icon
Flavor Text
Description
Probability
Storage Battery
"Give it some charge"
If used while empty, takes up to 3 pips of charge from Isaac's active item and stores it.
If used while the Storage Battery is holding charge, empties the Storage Battery and recharges Isaac's active item by the amount stored within.
Turns into a Corroded Battery at the start of the next floor.
10.00%
Corroded Battery
"Took a beating" / "About to burst"
If used while empty, takes up to 3 pips of charge from Isaac's active item and stores it.
If used while the Corroded Battery is holding charge, empties the Corroded Battery and recharges Isaac's active item by the amount stored within, before the Corroded Battery drops itself and explodes.
0.00%
Notes
Storage Batteries can have a random amount of charge stored in them when they spawn.
Pickups 
This page is about Batteries added in Fiend Folio. More information about Batteries in general can be found in the vanilla page.
Perfectly Generic Object.