SuperBANK Specs Explained: How to Read an Ultracapacitor Spec Sheet

What it is: The most important line on the sheet, and the one that explains all the others.

An ultracapacitor — also called a supercapacitor — stores energy electrostatically, as physical separated charge on an enormous internal surface area. A battery stores energy chemically, in a reaction that has to run forward to discharge and backward to recharge.

Why that changes everything:

an ultracapacitor gives you tremendous power very briefly; a battery gives you moderate power for a long time. They're complements, not competitors.

What it is: The standardized Battery Council International case designation — maximum case dimensions, terminal type, terminal placement.

What it tells you: Physical fit only. A group size is a shape, not a performance rating.

Why an ultracapacitor carries one at all: So it drops into a standard battery tray, clears a standard hold-down, and mounts where you'd expect. The SuperBANK is packaged in familiar automotive form factors specifically so installation doesn't require fabricating a mount.

Practical note: Like lithium, ultracapacitor banks weigh dramatically less than the lead-acid battery whose footprint they occupy. A light device in a tray built for a heavy one still needs to be properly secured — the hold-down isn't optional just because the thing is easy to lift.

What it is: The maximum working voltage of the bank. This is not a nominal rating.

Why this is different from a battery — and it's the single biggest misconception: A battery's voltage is a nominal design figure. A "12V" battery is called that regardless of its actual state of charge, and its voltage stays in a fairly narrow band across most of its usable range.

A capacitor doesn't work that way. Its voltage is its state of charge. Charge flows in, voltage rises; charge flows out, voltage falls — continuously and proportionally. There's no flat plateau. A partially discharged capacitor sits at a proportionally lower voltage, always.

This is why SuperBANK products are specified across an operating voltage range rather than a single number, and why the top of that range is what appears as the headline voltage figure. That figure is a ceiling, not a target.

Why you care — two things, both important:

Confirm the rated voltage against your alternator's output before you buy. A bank rated for a 12V system does not belong on a 16V setup, and vice versa.

What it is: Capacitance — the defining spec of any capacitor, the way amp hours are the defining spec of a battery. One farad is one coulomb of charge stored per volt.

What it tells you: How much charge the bank holds per volt, which drives both how much energy it stores and how much current it can deliver before its voltage drops.

Why the number is so much larger than you may expect: If you were around for the car audio capacitors of twenty years ago, you remember ratings in the low single digits — 1 farad, 2 farads, 5 farads — and the old rule of thumb about one farad per thousand watts. Ultracapacitor banks are rated in the hundreds and thousands of farads. That's not a typo or a different measurement scale; it's orders of magnitude more capacitance, achieved through a completely different internal construction. The comparison to an old-school stiffening cap is not a close one.

Why you care: Farads is the spec you use to compare one SuperBANK against another. More capacitance means more charge in reserve, more energy stored, and a bank that holds voltage more firmly through a heavy transient before it starts to sag.

Note on modularity: SuperBANK cells can be connected together to build a larger custom bank. Capacitance is the spec you're scaling when you do it, so it's worth understanding before you plan a multi-cell install.

What it is: The maximum power the bank is built to support, in watts.

What it tells you: The size of the system it can back up during peak demand — the practical, bottom-line number.

Why an ultracapacitor's number is so high for its size: Extremely low internal resistance. Power delivery is fundamentally limited by resistance, and an ultracapacitor's construction gives it far less of it than a battery of comparable size. That's why a bank weighing a fraction of an AGM battery can support system wattage the AGM can't touch.

The critical qualifier: This is a burst rating, not a sustained one. It describes what the bank delivers during the instant of peak demand — the exact moment a subwoofer hits a low note and your amplifier tries to pull hundreds of amps at once. It says nothing about how long the bank can carry that load, because carrying loads over time is not what it's for.

Why you care: This is the spec that solves headlight dimming and voltage sag on transients. It's also the spec that most directly explains what a SuperBANK is for: everything in your electrical system between the alternator and the amplifier has resistance and lag. An ultracapacitor sitting close to the load has almost neither, so it absorbs the spike the rest of the system can't respond to fast enough.

What it is: The ambient temperature range the bank is rated to operate across.

What it tells you: Where you can install it, and in what climates you can rely on it.

Why this is a genuine competitive advantage, not filler: Temperature is where battery chemistry fails you. Cold slows chemical reactions, so a lead-acid battery's output drops sharply as the temperature falls — exactly when a cold engine is hardest to turn over. Heat is worse in a different way: sustained high temperature is the leading cause of premature battery death, which is why batteries in Florida and Arizona routinely last half as long as the same battery in a cooler climate.

An ultracapacitor's electrostatic storage is far less temperature-sensitive on both ends. The rated range spans well below freezing to well above what an engine bay sees on a hot day.

Why you care — three real scenarios:

What it is: On this sheet — nothing. It's a dash, and that dash is deliberate.

Why it's blank: CCA is a standardized test measuring how many amps a battery delivers for 30 continuous seconds at 0°F while holding above a minimum voltage. That test is designed around a device that sustains a heavy load over time.

An ultracapacitor's entire design premise is the opposite: colossal current for a very short interval, then rapid recharge. Running a 30-second sustained test against a device optimized for sub-second bursts wouldn't produce a meaningful number, so rating one would be misleading rather than informative.

What this means practically: The absence of a CCA rating tells you something real about how a SuperBANK is deployed. In the typical installation it works alongside a battery, not instead of one. XS Power's design description of the product is precise about this: the bank delivers a surge of power to the vehicle's battery as it cranks, then recharges in seconds, ready to go again. The battery supplies sustained energy; the ultracapacitor supplies instantaneous power. Each does the job the other is bad at.

The secondary benefit is worth understanding too. By absorbing the hardest current demands, the bank improves voltage conditions across the whole system — which reduces stress on the battery, starter, relays, and control modules, and tends to extend their service life.

Bottom line: a blank CCA field isn't a missing spec. It's the sheet telling you honestly what this device is and isn't. Check the specific product's documentation for its intended role in the system before you plan an install.

What it is: Total stored energy — the same unit used on our lithium spec sheets, which makes this the one number you can compare directly across all three technologies.

What it tells you: How much energy is actually in the bank.

Why the number is small, and why that's honest: This is the trade-off for everything else on the sheet. Electrostatic storage is far less energy-dense than chemical storage, so an ultracapacitor holds a small fraction of the energy a battery of comparable size holds. Nothing on the spec sheet hides that, and it shouldn't.

For a capacitor, stored energy scales with capacitance and with the square of voltage — which is why a capacitor's energy falls off quickly as it discharges and its voltage drops. It also explains why higher-voltage banks store disproportionately more energy at the same capacitance.

Why you care — this is the spec that defines the boundary of the product: Watt hours is what tells you a SuperBANK is not a runtime device. It will not play your system with the engine off for any meaningful stretch. It will not carry your vehicle's electrical load if the alternator quits. Those jobs belong to a battery, and a big AGM or lithium pack will outclass any ultracapacitor on them by an enormous margin.

What the SuperBANK does instead is deliver its energy faster than anything else in your vehicle can, and take it back just as fast. Judge it on power delivery and voltage stability, not on runtime. Judged on runtime, every ultracapacitor ever made looks bad — because that's not the job.

What it is: The terminal hardware in the box.

Why it's on the sheet: So you know what you still need to buy. M6 terminal hardware is included, and adaptors are available separately if your cables are terminated differently — top post, side post, or ring terminal. Sorting this out before install day saves a trip.

Warranty is a spec, not fine print. Warranty length is a direct statement of expected service life, and it's the number that makes the cycle life rating concrete. Given that an ultracapacitor has very little to chemically degrade, the warranty term reflects a device built to outlast several batteries.

Instructions deserve more attention here than on a battery listing. Ultracapacitor installation has real requirements around wiring, fusing, and voltage limits, and a bank's behavior on first connection differs from a battery's. Download the instruction sheet from the product page and read it before the install, not during it.