Frequently Asked Questions

• How is EnerGenius DC different from other industrial and utility chargers?

  EnerGenius DC employs a modular architecture by which discrete power modules using modern switchmode technology are plugged into a backplane.  Power modules operate in parallel, so adding more modules adds more power.  Modules are “hot-swap”, meaning that they can inserted or removed while the charger is operating. Legacy industrial chargers are almost invariably monolithic, with discrete models for each power level.

• What's switchmode power conversion technology?

  Switchmode is a power conversion technology used for most power supplies and battery chargers in operation around the world today.   Switchmode power converters operate at high frequency instead of line voltage frequencies and take advantage of a fundamental attribute of power conversion: the size and weight of transformers is inversely proportional to their frequency.  This means that for any given power, switchmode power converters are much smaller and lighter than line frequency power converters such as silicon-controlled rectifier (SCR) designs.

• If they are so prevalent, why haven't I seen switchmode battey chargers applied to industrial and utility applications?

  They have been.  Outside of North America, industry and electric utilities employ switchmode chargers almost exclusively.  North American technical decision-makers have often not trusted that switchmode chargers would meet high reliability standards.  Much of this concern was justified as early trials of switchmode chargers – invariably repurposed units suited for more benign environments – did not turn out well.  SENS is different. We designed our EnerGenius DC chargers to stand up to the rigors of industrial and utility use.  SENS built in multiple layers of electrical transient protection of the type used in mission critical aerospace and military applications and designed a patented cooling system that prevents dust and airborne contaminants typical of many industrial and utility environments from contaminating electronic components.

• Other companies have attempted to sell switchmode chargers for industrial and utility applications. What is different about SENS EnerGenius DC?

  The difference is that SENS ruggedized EnerGenius DC to withstand the rigors of industrial use where AC power can be subject to transients, temperatures are often uncontrolled, and airborne contaminants are present.  In contrast, other companies have attempted repurpose rectifiers designed for telecommunications or CATV applications into industrial chargers.  This has been largely unsuccessful because their designers optimized these chargers for relatively clean facilities with conditioned power and air.

• Aren’t line frequency chargers more resilient to electrical transients than switchmode chargers?

  No.  It all depends on the design of the switchmode charger.  Decades of use in aerospace and military applications have proven that, when designed with the intention of resilience and reliability, switchmode power conversion is just as reliable as line frequency power conversion.  SENS itself has for years made both SCR and switchmode chargers for lower power applications.  A SENS internal company analysis showed that, over the first 6,000 units produced, our MicroGenius 2 switchmode chargers demonstrated 50% better hardware reliability than the corresponding first 6,000 of the predecessor line frequency NRG 10 charger.  One each of the first 6,000 chargers in each population failed due to apparent electrical transient.

  Switchmode converters are, in fact, inherently more vulnerable to mains-borne electrical transients than line frequency converters.  This is because power semiconductors in switchmode converters are located upstream of the converter’s power transformer, versus downstream of the transformer in line frequency designs.  This creates a dangerous vulnerability to electrical transients if designers do not employ careful protective measures.  SENS has employed such measures, using the same strategy as that used in aerospace and military systems: multiple layers of defense.

   

• What are the “multiple layers of defense” that SENS designed into EnerGenius DC?

  “Multiple layers of defense” refers to measures SENS has taken to protect the charger from electrical transients such as lightning and sudden AC voltages excursions that can take place in industrial and utility environments.

  The first and primary protection layer is a field-replaceable cartridge-type UL 1449 Listed surge protector connected directly to the charger’s input and output terminals. These replaceable devices offer very high surge current ratings to clamp transient energies at the charger terminals. This not only protects the front-end components of the system, including input wiring and connections, but reduces stress on non-replaceable surge protection devices located deeper in the system. This optional protection system is typically only needed in locations with exposure to frequent lightning.

  In each rectifier module additional metal oxide varistor (MOV) clamps and gas discharge tubes are incorporated into the electromagnetic interference (EMI) filter.  Together, these components protect the EMI filter capacitors and inductors, including clamping transient-induced resonances that would otherwise exacerbate voltage stress.  Surge clamping diodes in the boost converter are also provided to protect power devices from overstress. These diodes provide a path for excess voltage to bypass power switches and be absorbed in reservoir capacitors that can safely absorb the energy.

  Finally, all power electronics are enclosed inside sealed metal Faraday cages, which provides three benefits: Faraday cages provide a high degree of shielding from strong external radio frequency (RF) fields and minimize RF emissions from the converter itself.  Sealed metal boxes also prevent dirt and dust from accumulating on circuit traces and components.

   

• What AC inputs will EnerGenius DC accept?

  Although released models are optimized to accepted three-phase, three wire 480V AC input, EnerGenius DC will automatically accept other three phase or single phase input voltages.  Maximum output power for these variations are documented in the user manual.

• How do I know if a surge protection device (SPD) cartridge needs replacement?

  EnerGenius DC monitors the state of SPD’s and alerts users that a replacement is needed.  Alarms are displayed on the LCD display and communicated via Form C contacts and network monitoring protocols.

• What’s “forced conduction cooling”? How can you seal the electronics and still cool them?

  “Forced conduction cooling” describes the patented approach SENS uses to cool EnerGenius DC power modules.   Power modules consist of two primary circuit boards, each in a sealed aluminum housing sandwiched around a heat-exchanger channel.  Heat is conducted from warm components on each circuit board to the heat exchanger.   Redundant variable speed fans force cooling air through the channel, removing waste heat.   This approach is vastly superior to traditional approaches to fan-cooling of electronics because it eliminates the accumulation of failure-inducing contaminants such as dust, conductive dirt, and corrosives on circuit boards.   Contamination on printed circuits can cause short circuits between adjacent traces and components, causing both intermittent and catastrophic failures. Contamination that accumulates on and around components increases component temperatures by adding a layer of insulating dirt. The resulting temperature increase shortens useful life of components.   The accompanying photo exemplifies dirt and dust contamination in a normal fan-cooled power converter after only five years of operations in a non-humid, benign industrial environment.

• What happens if a fan fails?

  EnerGenius DC power modules employ highly reliable, redundant variable speed fans.  If a fan were to fail, the other fan would speed up to maintain the necessary cooling air flow.  The charger would raise an alarm, enabling the failed fan to be replaced on the next scheduled service call to the site. Fan replacement is easy and can performed in the field. Similarly, the charger monitors flow through the air filter and raises an alarm if the filter needs cleaning.  Filter cleaning and replacement are easily accomplished.

• How can EnerGenius DC be so much smaller and lighter than competing products?

  The size and weight of a charger’s isolation transformer is inversely proportional to its frequency of operation. This property enables the use of less iron in the transformer core and fewer wire turns as transformer operating frequency is increased. Switchmode converters exploit this principle by increasing the frequency at which all magnetic devices in the converter operate.

  Most industrial and utility stationary battery chargers use SCR (silicon-controlled rectifier) technology that convert power at AC input line frequency, 50 or 60 Hz.  EnerGenius DC’s isolation transformers operate at 100 kHz, about 2000 times higher.  Thus, the transformers and inductors in EnerGenius DC are vastly smaller and lighter than comparable magnetic components in SCR chargers.

   

• Why is smaller and lighter in weight better?

  Space is at a growing premium in equipment buildings as system integrators and end users try to reduce costs and be more space and weight efficient.  Smaller battery chargers consume less space and enable more mounting and location options, helping system designers fit more equipment into a given space.  Lower weight means easier installation and service.  EnerGenius DC “compact” and “wallbox” models can be installed without mechanical assistance, unlike comparably powered competitor units.  Lighter weight also means substantially lower shipping costs.

• Can I really save on shipping costs?

  Yes, and the savings are likely be hundreds of dollars to more than $1,000 per unit for larger configurations.  An LTL shipping cost comparison of two models of EnerGenius DC and competing 100A and 400A chargers for a 1,500-mile journey showed savings of between $300 and $1,000.

  EnerGenius DC and competitor models are shown in the comparison table shown here.

   

• Why does EnerGenius DC use so much less input current than competing SCR technology chargers?

  EnerGenius DC uses approximately 25% – 30% less AC current for the same output power for two reasons.  EnerGenius DC offers both higher efficiency and a much better power factor than line frequency chargers.  Efficiency is simply the ratio of output power to input power.  Power factor is a composite measurement of two things: the phase displacement between AC voltage and current consumed; and how well the current consumption waveform matches the AC voltage waveform. EnerGenius DC operates at near unity power factor meaning that its consumption of current is in phase with AC voltage, and it consumes current sinusoidally, with very little total harmonic distortion (THD).    Six-pulse SCR chargers, in contrast, operate at a poor power factor of 0.75 or less and impose THD on the incoming line of around 30% — a high level of harmonic distortion that some users cannot tolerate.

• Why does SENS think this modular approach will work in utility and industrial applications?

  Modular architectures have become the standard everywhere they have been employed, completely replacing old-style monolithic designs.  For example, 1980’s data centers almost universally employed very large disk drives, many the size of washing machines.  Now they are largely gone, replaced by paralleled arrays of tiny disk drives with a footprint smaller than most smartphones.  Large monolithic mainframe computers have given way to hot-swap blade computers that plug into a backplane and operate in parallel.  In the telecommunications industry, modular hot swap rectifier systems have rendered obsolete their monolithic predecessors.  In each case, modularity brings two compelling advantages: inherent redundancy and very easy servicing that turns a complex electronic device into a field replaceable unit (FRU) that can be field replaced by a non-specialized technician. These compelling advantages equally apply to stationary chargers. It is thus only a matter of time before modular stationary battery chargers become the standard for utility and industrial applications in North America. This technology shift in North America is predicted in a 2020 research report by Powertechresearch titled, Industrial Chargers – Analysis of United States Market.

• What are the advantages of the modular hot-swap approach for industrial and utility applications?

  Smaller size, lighter weight, N+1 redundancy, easier service. The technology employed to build hot-swap modular systems is both smaller and lighter than that used in legacy chargers, so EnerGenius DC is much smaller and lighter than legacy chargers.  See a comparison here.  Equally important is that modular technology easily allows for N+1 redundancy or even complete redundancy in a single package, providing an extremely high reliability unit.  Hot swap modules make service easy: The charger identifies which module requires replacement, enabling service personnel to swap in a new module in seconds without de-energizing the charger or DC system.  Control electronics automatically configure the new module into the system.

• What is N+1 redundancy?

  N+1 redundancy is an approach to ensure that the charger is always available.  N+1 refers to the number of power modules required to handle the application load, plus one more.  If any power module in the system fails, the remaining modules meet the full load requirement.  Service personnel can replace the failed module at the next scheduled maintenance call instead of making an emergency call.  The N+1 approach provides reliability close to that achieved by fully redundant systems, but at far less cost.  EnerGenius DC offers N+1 redundancy or 2N (conventional full redundancy) in a single package.

• What does hot-swap mean?

  How-swap means that EnerGenius DC’s power modules can be inserted and removed while the charger is operating without interrupting operation.  The charger’s control system automatically configures and provisions the new module to operate correctly in parallel with the existing modules.

• What happens if the charger’s control system suffers a failure?

  Power modules continue operation based on the most recent settings of the control system. This allows continued safe operation of the charger until the charger’s control circuit can be replaced.

• Can I get a completely redundant system in a single package?

  Yes, this is an option with the EnerGenius DC cabinet package.  Everything – input breakers, controller, power modules, displays, alarms, communications, backplanes and output breakers – can be redundant.  Users can connect to two different AC sources if desired.  The only common part is the sheet metal cabinet.

• Can I connect chargers in parallel?

  Yes.  A standard Ethernet cable is all that’s required.  Connected chargers will automatically share load.

• Can I add power to a system after it’s installed?

  Yes.  You can add hot-swap power modules to both wallbox and cabinet style chargers up to the rated capacity of the charger.  At the time of the original order, users specify the current carrying capacity for cabinet systems which in turn determines backplane, wiring and breaker sizes.   For example, a cabinet system could be ordered with the capacity to supply 125V, 300 A (nominal), but initially be populated with only enough power modules to deliver 200 A.  Additional modules could later be added up to the 300 A limit for that system.

• What about EnerGenius DC’s output power quality and responsiveness to changes in load?

  EnerGenius DC’s produces such high-quality DC power that it can operate as a power supply with no battery connected.  Output ripple is inherently low because the charger’s output filter operates at 400 kHz, which is between 1,000 and 6000 times the frequency of legacy line frequency chargers like SCR.  And because energy is converted at high frequency, the charger’s dynamic response is nearly instantaneous – 8ms for load changes 50% of rated output.  This combination of power quality and dynamic response is impossible for legacy type SCR chargers to achieve.  To even approach the low ripple DC delivered by EnerGenius DC, SCR chargers employ heavy and bulky inductors and capacitors, which add weight and cost, plus substantially slow dynamic response.

• What AC inputs will EnerGenius DC accept?

  Currently released models designed for three-phase, three-wire AC from 380-480 volts but operate with derated output on any single or three-phase supply of 208 volts or higher.   Future variants will be optimized for other AC inputs.

• What DC output voltages are available?

  Nominal DC outputs of 120 volts and 240 volts are currently available.  Chargers with nominal 120-volt DC output can be adjusted from 0 to 150 volts.  Nominal 240-volt DC chargers can be adjusted from 0 to 300 volts.  Additional DC output options will be available in the future.

• What alarms are available?

  Alarms are annunciated visually on the front panel, via either standard or high-power Form C relay contacts, and using standard network protocols.   Depending on the customer’s application, SENS has default alarm profiles, but users can select from over 100 alarms and map them to the display and Form C relays using the SENS Setup Utility.  Users can define alarm delay times and specify whether relays are latching or non-latching.  Using input relays on the optional battery monitor accessory, users can even set alarms based on external inputs such as an H₂ sensor. Powerful battery monitoring options will be released in the future.

• What are the ratings of EnerGenius DC’s Form C relay contacts?

  Compact models include five standard relays (30 volts, 2 amps) and two optional high-power relays rated at 120 volts AC, 5 amps.  Wallbox models include five standard relays (30 volts, 2 amps) and two optional high-power relays rated at 120 volts AC, 5 amps or 240 volts AC, 3 amps. Cabinet models include nine standard relays and up to four optional high-power relays. All relays are assignable and can be configured as either latching or non-latching.

• What batteries can EnerGenius DC safely charge?

  EnerGenius DC can charge any type of industrial stationary battery: Flooded lead-acid, VRLA, NiCd, and lithium.  EnerGenius DC is already fully qualified to work with Saft Flexion lithium batteries, and SENS can easily integrate battery management systems (BMS) necessary for safe operation of other lithium batteries.  For NiCd batteries, EnerGenius DC’s commissioning mode automatically prepares batteries for initial use.  Operators can start commissioning mode and after the charger completes commissioning, it automatically enters its normal charging mode.  No user intervention is required after commissioning.

• Is EnerGenius DC UL-listed?

  Yes.  Specifically, it is C-UL Listed for US & Canada: CSA 22.2, No. 107.2, UL 1012, UL 508A.  It is also CE marked for the European Union.

• What industry standards does EnerGenius DC meet?

  All models meet NFPA-70 and NEMA PE-5/IEEE 2405.  PIP (Process Industry Practices) standard compliance is available as an option.

• What remote communications protocols are available? Can I add these in the field?

  Modbus, DNP3, and IEC 61850 are all available.   After mid-2021, users can easily add any of these protocols in the field by purchasing a license key from SENS.  No additional hardware is needed. When the unique key for that unit is entered through the SENS Setup Utility, the charger automatically activates the network protocol.

• How do I change charger settings?

  Users can make settings changes using either the front panel or the SENS Setup Utility using a USB connection to a PC.  Most changes can be made from the front panel.  More detailed changes such as alarm relay assignments utilize the Setup Utility.

• Will SENS customize EnerGenius DC to meet specific requirements?

  Yes. And, because the modular EnerGenius DC design includes a huge array of standard features, factory options and user-configurable settings many chargers will meet a wide array of specifications and customer requirements without customization.  Contact the SENS sales team to determine which solution is most appropriate for your application.

• Where was EnerGenius DC designed? Where is it made?

  SENS designed and builds EnerGenius DC at its facilities in Longmont, Colorado, U.S.A.