Dad's Battery is a passive item in Fiend Folio, a mod for The Binding of Isaac.

Allows active items to be used without having the amount of charges required. This will convert all excess charge to a negative charge, which is marked with red bars starting from the top of the charge bar.

Negative charge reduces Isaac's speed: SpeedStat + (0.1 - SpeedStat) * NegativeCharges, and shot speed: ShotSpeedStat + (0.6 - ShotSpeedStat) * NegativeCharges.

Speed cannot go below 0.1, and shot speed cannot go below 0.6.

Negative charges must be replenished normally (clearing rooms or picking up batteries) before being able to use the active item again.

Switching active items does not get rid of the negative charge. It will persist until fully replenished.

The negative charge can go up to 12 bars for every item.

Dad's Battery can be found in the following item pools:

• Check out the item description on the mod's external Wiki.
• Download Fiend Folio from the Steam Workshop.