XS Power SB500-51R 12V 4000 Watt 500 Farad Super Capacitor Bank

The XS Power SB500-51R is a 12V super capacitor bank that stores current and releases it the instant your system asks for it. It is rated at 500 farads and 4,000W max power, works across a 12.0 to 16.2V range, and fits a BCI Group 51R footprint with reverse terminals so the posts line up with factory cabling.

In a high-power audio build, the SB500-51R covers the current spikes that pull system voltage down on heavy bass notes, which keeps amplifiers working in their happy range instead of clipping. In a starting system, it sends a surge of power to the factory 12V battery while the engine cranks, then recharges in only a few seconds and is ready for the next start. Steadier cranking voltage puts less stress on the battery, starter, relays, and engine control modules, which lowers the odds of an expensive electrical repair down the road.

Capacitor cells also hold up where lead acid chemistry slows down. On a cold winter morning, the bank adds a burst of current to a slow-cranking AGM battery. Rated for more than a million cycles, it suits commercial vehicles and everyday vehicles alike and commonly stays in service past a decade.

Multiple cells can be connected together to build a larger custom power pack sized to your draw, so the same bank scales from a single-amplifier system to a competition SPL install, a work truck with heavy accessory loads, or a show vehicle that idles for long stretches. At 11 lb, it adds very little mass, and M6 terminal hardware is included.