Volts

Volts are small white pickups dropped by Enemies when they are destroyed.

Boss phases also drop them - either gradually until they are destroyed, all at once when they are destroyed, or both (depending on the boss)

Collecting them allows you to upgrade your primary weapon up to a maximum of Level 3 (starting at Level 0). Higher reinforcement levels require more Volts.

The amount of Volts an enemy spawns is indicative of how much progress is gained towards spawning the next Battery. See Battery#Spawning_algorithm.

Volts required for reinforcement

Reinforcement level	Volts required	Cumulative volts
Level 1	10	10
Level 2	50	60
Level 3	100	160

Volts dropped by each enemy

Enemy	Volts dropped
Keg	2
Hunter Keg	3
Mega Keg	9
Bomber Titan	8
Blaster Titan	7
Buster Titan	8
Drone	3
Turbo Drone	4
Bullet Turret	7
Laser Turret	9
Maser Turret	11
Mine	2
Super Mine	8
Wasp	1 per 3 killed
Rocket Fido	2
Fetcher Fido	4
Jumbo Fido	8
Orbital Factory	18
Vector Factory	12
Tendril Factory	5
Wasp Tank	0
Mine Tank	0
Reaper Spectre	6
Banshee Spectre	7

Naming

"Volts" is the name used by game files and by the developers. They are also referred to as "Energy" in the tutorial.