9 Volt is a passive item.
Effects
- Fully charges the current activated item upon first pickup.
- If the current activated item has a recharge time of more than 1 bar, then it will grant 1 bar of charge whenever the item is activated.
- If the current activated item has a recharge time of 1 bar, then it will change the item to have a timed recharge of 15 seconds. The recharging of the item only triggers so long as there are enemies present in the room in any fashion. Empty rooms do not cause recharging to start.
- An enemy spawned in a cleared room will also cause recharging to start.
- If the current activated item has a real-world unit-based recharge time, the effect of the 9 Volt may vary.
Interactions
Sharp Plug - Renders the Sharp Plug unusable. Sharp Plug can only be used if the item is at 0 charge, but 9 Volt instantly gives +1 charge to the item upon activation.
Synergies
- 2-bar items - Fills the entire gauge in a single room, effectively granting the opportunity for the item to be used every room.
- 3-bar items - Quadruple rooms and L-shaped rooms give 2 bars after clearing them, allowing one free use of the item in those rooms if the gauge is full upon entering them. It can also be used at the beginning of a Boss Challenge Room to get the full charge back after beating both bosses.
- 4-bar items - In a Challenge Room, if the item is used during the first wave, it will get all its charge back at the end.
- AAA Battery - Even faster item charging (9 Volt gives 1 extra bar after any item use, while AAA Battery reduces the number of bars required for using the activated item).
- AAA Battery + 3-bar items - The item can be used every room as with 2-bar items.
- AAA Battery + 4-bar items - Same as the 3-bar item synergy without AAA Battery.
- The Battery - Charges faster and stores an extra level of charge, although AAA Battery synergies do not work with the extra level of charge.
- The Candle - The Candle starts at half charge after use.
- Red Candle - Red Candle recharges quicker than normal.
- Brown Nugget - Brown Nugget starts at half charge after use.
3-bar items - Quadruple rooms and L-shaped rooms give 2 bars after clearing them, allowing one free use of the item in those rooms if the gauge is full upon entering them. It can also be used at the beginning of a Boss Challenge Room to get the full charge back after beating both bosses.
Notes
- Enemies generated through a slot machine, shell game beggar, or breaking pots/skull will restart the charging process, even though a cleared room still counts as cleared if enemies are spawned in it.
In-game Footage
Unlockable achievements
Template:Achv Template:Achv
Trivia
- This item is used in When Life Gives You Lemons (challenge #12), Beans! (challenge #13), and It's in the Cards (challenge #14).
 Batteries
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 The Binding of Isaac: Rebirth
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