Scope

The purpose of this document is to provide an understanding of what makes KAPower supercapacitors / ultracapacitors unique for engine starting or high pulse-power applications.  The document will briefly examine lead-acid (a.k.a. SLI battery (starting, lightning, ignition)) starting batteries and electrochemical double layer capacitors (ELDC), electrochemical capacitors (EC), supercapacitors, or ultracapacitors.  As such, the document is divided into five main sections.  Those sections being: (1) What is KAPower? (2) Understanding a lead-acid battery and its drawbacks, (3) Understanding a capacitor, (4) Understanding a Symmetrical EC, supercapacitor, or ultracapacitor and its shortcomings, and (5) What makes KAPower unique?

Furthermore, for the purpose of this document, it is important to understand the differences between the terms energy and power.  Energy is defined as power over time (how long) and power is defined as the rate at which energy is released (how much).  In addition, the terms electrochemical double layer capacitor (EDLC), electrochemical capacitor (EC), supercapacitor, and ultracapacitor are used synonymously throughout the document.

What is KAPower?

KAPower is a next generation energy storage device that will provide upwards of 15 – 20 years or approximately 1,000,000 cycles of service.  KAPower is an asymmetrical electrochemical double layer capacitor.  Otherwise known as an electrochemical capacitor, supercapacitor, or ultracapacitor.  KAPower is an alternative or counterpart to lead-acid (SLI) engine starting batteries or an alternative or counterpart to batteries used in high pulse-power applications.

Understanding a lead-acid battery and its drawbacks

A battery is a device that stores its energy for a later release.  It is an electrochemical device that converts chemical energy into electricity.

A battery is made from galvanic cells.  Each galvanic cell consists of an anode, cathode, separator, and an electrolyte.   A lead-acid battery’s galvanic cells are made from lead plates (anode), lead dioxide (cathode), a separator, and diluted sulfuric acid (electrolyte).  The electrolyte allows a chemical reaction inside the battery to store or release voltage.  When the chemical reaction takes place, electrons flow through conductors to create electricity.  During discharge (energy or power demands), the electrolyte reacts with both plates changing both the anode and cathode surfaces to form lead sulfate.  When the battery is charged, the chemical reaction reverses and the plates transform back to lead and lead oxide storing the energy.  This chemical process is repeated during the life of the battery.  It is important to note that the process is a chemical process, not a physical process.  Lead-Acid batteries do not create energy.  Energy is stored or released by using the chemical process to charge or discharge the plates.   The chemical process is one of the primary differences between a lead-acid battery and a capacitor. 

Lead-acid batteries excel at being very energy dense devices but have difficulties when asked to produce large amounts of power.  Especially when the power demands involve high power applications like engine starting.  Collective internal resistance is the greatest contributing factor why lead-acid batteries have difficulties generating large amounts of power.  As a result, internal resistance positions a lead-acid (SLI) battery at a huge disadvantage for abrupt power demands such as engine starting when compared to KAPower supercapacitors /ultracapacitors.

Manufactures of lead-acid (SLI) (a.k.a. SLI battery (starting, lightning, ignition)) starting batteries have had to compromise the lead-acid battery’s life to tolerate the power demands associated with engine starting and repetitive high pulse-power applications.  Thinning the plates and adding extra plates inside the battery have compromised the design.  In addition to the plates being thinned, the lead is applied to the plates in a sponge-like form.  Using a sponge-like form increases the surface area of the thinned plates to achieve maximum power while at the same time generating a minimal amount internal resistance.  The compromised design enables the battery to accentuate power rather than energy.  However, the compromised design does not come without drawbacks since a lead-acid (SLI) battery uses a chemical process to store and release its energy.

A lead-acid (SLI) battery’s chemical process will cause the thinned plates to suffer “positive grid corrosion.”  Positive grid corrosion is a result of the chemical process during the charging and discharging of the + plates.  Each time the battery cycles there is a slight depletion of the lead on the + plates.  Eventually the + plates get eaten away until there is nothing left.  The thinner the + plates the greater the power vs. energy, but as a result, the thinner the + plate the easier and quicker + plate corrosion.    As a result, + plate corrosion is one of the primary reasons for a lead-acid (SLI) starting battery’s failure.

Lead sulfation is another large contributing factor why lead-acid batteries have difficulties generating abrupt power for demands such as engine starting.  Lead sulfation occurs naturally inside a lead-acid (SLI) battery.  During normal use small amounts of sulfate crystals are formed.  Generally the small amounts of sulfate crystals are not harmful.  However, when a lead-acid battery experiences a continued charge deprivation, the small amounts of sulfate crystals become a stable crystalline that attaches itself to the negative (–) plates.  Over time, the crystalline attached to the – plates become large and form crystals.  The crystals adversely affect the battery’s ability to generate power and increase the battery’s internal resistance.  In addition, over time, the sulfite crystals can cause a “soft-short” that increases the lead-acid (SLI) battery’s self discharge rate.  In turn, making it even more challenging to keep the lead-acid battery fully charged.

Maintaining a fully charge battery can help minimize sulfation.  Yet, maintaining the full charge can be challenging.  It is assumed that once an engine is running it will charge a lead-acid (SLI) battery back to a full charge.  In most scenarios, the assumption is incorrect because an engine at lower speeds, or at idle does not provide a sufficient amount or duration of charge.   The charge will be insufficient to combat the effects of irreversible sulfation.  Charging a lead-acid battery can take hours depending on the lead-acid battery’s state of charge.

The state of charge (SOC) has a direct impact on the sulfation, performance, and life of a lead-acid (SLI) battery.  Per the chart below it can be seen that there is a very small voltage window for a battery to be considered “Fully” charged vs. “DEAD.”  There is only ~ 2.2 volts difference between being “Fully” charged and  “DEAD.”  A battery at ~ 12.50 volts is actually only at 90% SOC.  At 90% SOC a lead-acid (SLI) battery will still be experiencing corrosion and sulfation issues.  With such a small amount of voltage tolerance, it is easy to see why a lead-acid starting battery has a compromised life.  Any time a lead-acid (SLI) battery changes its voltage it negatively affects its life.

State of charge (SOC)

To add to the difficulty of maintaining the state of charge, there is a direct correlation between temperature and the amount of time needed to realize a 100% state of charge.  A lead-acid battery has a large thermal mass that results in the internal temperature of the battery changing at a much slower rate than the surrounding temperature.  The lower the internal temperature of the lead-acid battery, the greater the internal resistance.  The increased resistance results in longer charge cycles and further hinders the lead-acid (SLI) battery’s ability to discharge power in power demanding applications such as engine starting.

Other factors contributing to a lead-acid (SLI) battery’s increasing internal resistance, poor power performance, and diminishing life

Acid Stratification
Acid stratification occurs when a battery’s acid is concentrated heavily on the bottom of the battery vs. the top of the battery.  Like sulfation, acid stratification is caused from a lead-acid (SLI) battery being deprived of a full charge.  Acid stratification is usually a result of the colder winter months.  During the colder winter months it becomes difficult to fully charge a cold battery because of its large thermal mass.  Short trips to and from various destinations are insufficient to heat the battery’s large internal mass.  As a result, the battery’s internal resistance is increased requiring longer charge times to become fully charge.

Charging at a rate that is too fast or too slow
It is important to charge at a proper rate since charging contributes to the same drawbacks a lead-acid (SLI) battery experiences during discharge cycles  (i.e. Plate Corrosion, Sulfation, etc.).  Battery manufactures cannot control the rate of a discharge cycle but they can recommend the amperage rating on the charge cycle.  By recommending and controlling amperage rating on the charge cycle, lead-acid starting battery manufactures can offer ways to minimize the charging drawbacks associated with lead-acid (SLI) batteries.  Note that the drawbacks cannot be eliminated only minimized.

Not allowing the battery to rest between cycling
No rest results in a higher state of charge on the outer plates than the state of charge on the inner plates.  Resting helps the lead-acid (SLI) battery balance the charge between the plates.

Water loss due to overcharging (overheating the battery), or exposure extreme high temperatures
As a lead-acid (SLI) battery “heats,” the battery vents gases that contain moisture.  Over time, the venting gases diminish the water in the electrolyte and can cause a lead-acid battery to fail prematurely.  Regardless of the lead-acid (SLI) battery type, starting, sealed, or absorbed glass matt (AGM), all are subject to venting.  There is no such thing as a vent free lead-acid battery.  The rate and amount a lead-acid battery vents gases is directly proportional to the amount of heat generated.  It is important to note that the venting gas contains a potential explosive mixture of Hydrogen Gas.  The hydrogen gas is a byproduct of charging a lead-acid (SLI) battery.  Therefore, it is recommended that a battery is located in an area that provides adequate ventilation.

Further adding to the drawbacks associated with lead-acid (SLI) batteries are banks of lead-acid batteries used for engine starting or high pulse-power applications.  Banks of batteries consist of two or more batteries grouped together.  Grouping batteries together enables the group to have a larger energy reserve and/or a different voltage than a single battery.  (i.e. Two 12 volt batteries connected in series becomes 24 volts).  Conversely, there are drawbacks to using banks of batteries.  Similar to a single battery, a bank of batteries voltage response uniformly alters with age.  If a battery inside the group is replaced, the new battery will increase its rate of self-degradation until it is at the same level as the battery bank.  At the same time, the new battery increases the self-degradation of the other batteries in the bank.  It is like a “double edged sword” but in this instance it is undesirable.  It is recommended replacing the entire battery bank rather than just a single battery since the battery bank is only as strong as its weakest battery.

A lead-acid (SLI) starting battery’s escalating internal resistance places the lead-acid battery at a huge disadvantage when compared to KAPower for producing power for engine starting or other high pulse-power demands.  It is inevitable that as a lead-acid (SLI) battery discharges and charges the internal resistance will increases and the power performance will decrease.  As a result, an ideal application for a battery would by an application requiring energy over time rather than an abrupt power demands.

Understanding a capacitor

Similar to a battery, capacitors are an energy storage device that is capable of storing energy for a later release.  However, that is where the similarities end.

A simple capacitor consists of two electrodes surrounded by an electrolyte.  When voltage is applied, electrons are attracted to, and equally attach themselves to the electrodes in an opposite manner.  When the voltage is removed, the electrons stay attached to the electrodes and the capacitor is now charged.  The charge is stored on the surface of the electrodes until the capacitor is asked to release its energy.  Unlike a battery, the process is a physical process and not a chemical process.  As a result, the internal resistance or amount of time need to release energy inside a capacitor is drastically less than that of a lead-acid (SLI) battery.  The discharge and recharge process may be repeated over and over without any of the drawbacks associated with lead-acid (SLI) batteries.  Capacitors can be cycled rapidly, experience no degradation of their performance, and have a virtually unlimited lifespan.

Electrochemical double layer capacitors (ELDC), EC’s, supercapacitors, or ultracapacitors are similar in design to a simple capacitor except they collect a double layer of electrons on each of the electrodes.  In most designs, the electrodes are made from carbon so that the surface area of the electrode can be exploited.  One tablespoon of the carbon used inside KAPower has approximately the same surface area of a football field.  The vast and dense surface area of the carbon enables KAPower to store large amounts of energy in an extremely small amount of space.  Unlike a lead-acid (SLI) battery, the energy rests on the electrodes using a physical process not a chemical process.  Therefore, there is minimal internal resistance and the energy is easily converted into high power for engine starting or other high pulse-power applications. 
 
Presently there are two common variations of EC’s, supercapacitors, or ultracapacitors used for engine starting or high pulse-power applications.  The first design is symmetrical and the second design is asymmetrical.  A symmetrical ultracapacitor uses the same materials for each electrode, a non-conducting separator, and an electrolyte inside its design.  An asymmetrical supercapacitor uses a single carbon electrode in conjunction with an additional electrode of a different material, a non-conducting separator, and an aqueous electrolyte inside its design.  KAPower is an asymmetric EC, supercapacitor, or ultracapacitor and is unique in its design and performance when compared to symmetrical, EC’s, supercapacitor, or ultracapacitors.

Understanding a Symmetrical EC, supercapacitor, or ultracapacitor and its shortcomings

Symmetrical EC’s, supercapacitors, or ultracapacitors, are powerful devices but have shortcomings when used for engine starting or high pulse-power applications.   The shortcomings of a symmetrical design include a high self-discharge rate, the need for voltage balancing between the cells, the type(s) of electrolyte, and the methodology used to enclose each of the cells.

A high self-discharge rate is inbred in the design of a symmetrical EC’s, supercapacitors, or ultracapacitors.  A symmetrical module is made from combining individual symmetric cells in parallel or series to create a module.  The number of cells determines the voltage and power capabilities of the module.  Once the cells are combined, the cells almost always require a circuit that intertwines the cells and monitors each cell’s individual voltage.  Maintaining a balanced voltage between the cells is important.  Some designs actually discharge the cells down to zero volts in order to insure no cell imbalance occurs.  Other designs monitor each cell, with electronic circuits, and will apply a load on the cells that have a higher voltage.  The load brings the cells down to a voltage equal too or within a tolerance to the lowest individual cell.  As a consequence, the continual voltage monitoring and balancing causes the symmetrical module to have a comparatively high self-discharge rate compared to KAPower.  KAPower does not require any cell-balancing mechanisms.

Voltage balancing between the symmetrical cells in a module is needed in order to avoid overcharging of the individual cells.  Every cell that is manufactured will have a tolerance or characteristic unique to itself.  The recharge, discharge, and degradation (self-imposed discharge) rates will fluctuate from cell to cell.  Under use, the individual cell voltages’ will tend to become a variable within the string of cells, or module.  When the cells are recharged as a module, no single cells voltage level should exceed the maximum allowable voltage specified.  If the maximum allowable voltage is exceeded, the electrolyte will begin to gas.  Most symmetrical supercapacitors or ultracapacitors use an organic electrolyte.  Organic electrolytes are a natural desiccant and cannot be exposed to the atmosphere without rapid degradation.  Consequently, the cells are hermetically sealed.  If the cell gasses too much, the pressure within the cell will cause the hermetic seal to rupture or explode.  If the cell ruptures or explodes, the damaged cell will render the entire module useless.   In addition, the module can pose a danger since most organic electrolytes are flammable and toxic.  Certain electrolytes create cyanide gas when combusted or burned.  It is very important from a safety perspective to balance the voltage between the symmetric cells in an ultracapacitor module.  The cell balancing is needed in order to prevent any voltage imbalance that may create or allow a catastrophic failure of the symmetric cells or module.

What makes KAPower unique?

KAPower is unique and has none of the drawbacks associated with lead-acid (SLI) batteries or shortcomings associated with symmetrical ultracapacitors.

KAPower supercapacitors use carbon electrodes in conjunction with nickel electrodes, a non-conducting separator, and an alkaline electrolyte (potassium hydroxide solution) inside each cell to store its energy.  The carbon and nickel are different, and as such, have unequal (asymmetric) amounts of surface area for collecting energy.  In the KAPower design the capacitance from the smaller electrode becomes approximately absolute vs. a symmetrical EC’s capacitance being half the total capacitance of one of the equal carbon electrodes.  As a result, the asymmetric design may effectively double the capacitance value when compared to a symmetrical design.  In addition, nickel has an exemplary high specific capacitance that allows the asymmetric design to exhibit a “Faradaic pseudo-capacitive behavior.”   When the asymmetric cells are combined to form a module (KAPower), KAPower’s characteristics are ideal for engine starting applications or other high pulse-power applications. 

KAPower’s energy is stored using a physical process instead of a chemical process.  Therefore, KAPower does not suffer the drawbacks associated with a lead-acid starting battery.  KAPower will not experience plate corrosion, sulfation, acid stratification, or degradation from use or age.  KAPower also does not require any complex charging specifications and can be recharged in as little as 15 seconds.  Additionally, KAPower does not require extended rest periods as desired with lead-acid (SLI) batteries.

The internal resistance of KAPower has a low dependence on the state of charge (SOC) and temperature.  KAPower can crank an engine with as little as 9 volts.  Comparatively, a lead-acid (SLI) battery cannot provide sufficient power to crank an engine with as little as 11.7 volts (~30% SOC).  Temperature hinders the lead-acid battery’s SOC power levels even further.  As the temperature decreases, a lead-acid (SLI) battery’s internal resistance increases, directly impeding the SOC power output. KAPower’s power output is virtually unaffected by lower temperatures and SOC.  KAPower is designed to provide power in temperatures as cold as -40° F.  KAPower’s low internal resistance allows KAPower to crank an engine and charge itself even in a “Dead” battery situation.  KAPower is the only supercapacitor or ultracapacitor device that allows cranking below the level of a “Dead” battery.  Thus, no-starts from a “Dead” battery are eliminated.

The simple design of a KAPower does not require any internal cell balancing like a symmetrical ultracapacitor modules.  As a consequence, KAPower’s self-discharge rate is very low and can store enough energy / power for engine starting or high pulse-power applications for months in-between use.  If KAPower happens to loose its charge during storage, it can be recharged in as little as 15 seconds.  Subsequently, KAPower will produce full power for its intended application.

KAPower is safe and use a Potassium Hydroxide (KOH) solution as an alkaline electrolyte.  KOH is an inorganic electrolyte and unlike organic electrolytes, KOH supercapacitors / ultracapacitors are non-flammable and non-toxic if burned.  KOH is not a natural desiccant and can be exposed to the atmosphere without degradation.  As a result, KAPower is not required to be hermetically sealed like symmetrical EC’s that use organic electrolytes.  KAPower uses KOH for its safe high conductive properties.

The asymmetric nickel carbon design of a KAPower allows a single 120-kilojoule module to have approximately the same combined power output of 4 Group 31 lead-acid (SLI) batteries.   On average, a single Group 31 lead-acid (SLI) battery weighs approximately 68 lbs.  A battery bank of 4 group 31 batteries weighs nearly 272 lbs.  A single 120-kilojoule KAPower module weighs roughly 60 lbs.  That amounts to a difference of 212 lbs.  KAPower offers a substantial weight and space reduction that will directly contribute to the efficiency of the vehicle or vessel KAPower is installed on.  In addition, the power potential inside KAPower remains relatively constant for approximately 15 -20 years. 

KAPower supercapacitors contain no lead.  Lead is considered a “heavy” metal and is highly toxic to humans and the environment.  According to a 2003 report titled “Getting the Lead Out” by the Environmental Defense and the Ecology Center of Ann Arbor Michigan, it is estimated that lead-acid batteries in vehicles on the road contained a projected 2,600,000 metric tons of lead.  Additionally, the Battery Council International, in 2010, estimated that there where 119.6 million units of U.S. Domestic lead-acid battery shipments.  Based on the sheer tons and shipments of lead-acid batteries, there is substantial challenges faced with proper disposal.  KAPower does not have the challenges of proper disposal associated with lead-acid batteries since KAPower contains no lead.  Additionally, the average life of KAPower is 15 – 20 years or approximately 1,000,000 cycles vs. a lead-acid (SLI) starting battery’s life of 1 – 4 years or approximately 400 cycles.  By using KAPower there can be a substantial decrease in the amount lead used for engine starting and high pulse power applications.

KAPower supercapacitors / ultracapacitors vs. lead-acid (SLI) starting batteries

 KAPower asymmetric vs. Symmetrical EC’s