PowerForma FAQs

1. Can a Supercap stack connect to and supply backup power to a 48 VDC and lower via the DC BUS battery connection?

Yes. There are 12VDC, 24VDC, 36VDC and 48VDC options in various kWh sizes. Most
commonly 48VDC nominal is used. Parallel connection to the appropriately DC BUS is
common.

1. Can a stack connect to and supply backup power to a 48 VDC and lower via the DC BUS battery connection?

Yes. There are 12VDC, 24VDC, 36VDC and 48VDC options in various kWh sizes. Most commonly 48VDC nominal is used. Parallel connection to the appropriate DC BUS is common.

2. Can a Supercap stack (instead of the current VRLA battery string) provide 100 amps at +48 VDC for 36 hours to supplement rectifier operation when commercial power is not available to the DC BUS?

For 100A for 36 hours, the recommendation is to use 28 of the 7.4kWh, 48VDC (nominal) modules @ 90% DoD.

3. Can the 48VDC option be connected to any commercial off the shelf DC BUS rectifier? Does it require a specific rectifier?

Commercial rectifier use is common. The recommended operating voltage range is a minimum of 47VDC to a maximum of 57VDC. Any rectifier that can provide charge control within this voltage range is acceptable.

4. The program is trying to confirm whether the super cap can replace the current battery and plug and play with the current DC BUS. Please confirm if/when specs can be available on the rack that accommodates super caps. Please confirm whether SupeCap Energy can provide an estimated equipment price on the 16 modules needed for the application.

Yes, these are interchangeable provided the charge controller is capable of variable settings to accommodate the supercaps.

5. Are published rates (amps, hours to end of cell voltage at 77°F (25°C) available to support 48 VDC module capacity testing. Please confirm when published rates (amps, hours to end of cell voltage at 77°F can be available for review for 48 VDC application?

The spec sheet data is based on 25 degrees C, i.e., 77 degrees F. Ah available based on nominal voltage of 51.2VDC is 146Ah.

6. Does the 48 VDC module and rack comply with IBC seismic testing and requirements?

Yes we can provide these for zone 4 seismic applications.

7. We typically do not solicit custom equipment but instead solicits (through AMS) for commercial off the shelf (COTS) equipment that meets IBC requirements?

This is not a problem, we will use a commercially available rack that is seismic rated.

8. Does the 48 VDC module have a specification on ripple current, EMI or audible noise? Please confirm when specification can be available?

We have not experienced any of these effects. We will ask the manufacturer whether specs are published. We will provide when available.

9. What can happen to a 48 VDC module if it is discharged more than 90% (spec notes recommend discharge less than 90%)?

The internal BMS will shut down the module at the minimum voltage which would be equivalent to 100% DoD. The module will restart when voltage is applied and back within operating range. In other words, it will discharge 100% with no damage to the product. Operation within the BMS limits and rated capacity is what determined the 90% DoD recommendation. A 7.4kWh module provides 7.35kWh useable energy at 90% DoD.

10. Please confirm what BMS stands for. Please confirm what voltage the module restarts at.

Battery Management System. These are built into each module when discussing low voltage systems and supplied as an external BMS unit when discussing high voltage systems (>400VDC nominal). The module restarts at the spec sheet stated minimum voltage.

11. What can happen to a 48 VDC module if it is discharged more than 100% (spec notes max depth of discharge 100%)?

It cannot discharge more than 100%. But as stated above, it will shutdown and then recover when voltage is reapplied.

12. Please confirm the reliability (.999?)of the super cap module and the super cap rack. Please confirm any known failure modes (short, open, both, other) for a super cap. Please confirm whether a super cap can explode during normal operation and during abnormal operation.

Our estimate for an installed system is above 99.999%, as loss of a single module in a parallel connected system would not result in system shutdown, just diminished total capacity (kWh). Supercapacitors have been available and in use for about 5 years as energy storage solutions. From our experience, typical failures, if they do occur, do so in the BMS, not the cells. The BMS is a replaceable part. Because a typical system is built with multiple modules installed in parallel, reliability for the “system” is significantly higher than 99.999%, given loss of a single module will not cause a system failure. We have never experienced a short circuit failure. All BMS failures result in open circuit failure, i.e., the module simply will not run for a specified reason shown in the BMS display or provided remotely via Modbus alarm. Supercaps cannot explode and their specific design precludes dendrite growth which is the leading cause of cell short circuit failure in chemical batteries. Thermal runaway is not possible in a hybrid supercap architecture.

13. What can happen to a 48 VDC module if applied voltage exceeds 58 VDC?

The BMS will stop charging the module.

14. How does the BMS work?

The BMS is a firmware controller that monitors various aspects of battery health, including max/min voltage, current limits, and temperature. It directs the circuitry in the solid state relays which in turn, manages the mosfet transistors’ aggregation and delivery of cell energy. The limits are set based on the cell capabilities in aggregate (their combined voltage, current and temperature capabilities).

15. What can happen to a 48 VDC module if the applied voltage is less than 46 VDC?

The Module won’t take a charge.

16. Does the 24 VDC module provide remote monitoring?

The modules support Modbus. We offer an optional Edge-of-Network solution for remote monitoring using either a hosted or private Cloud solution speaking with the EoN devices. Each EoN is capable of monitoring16 modules in parallel. Additional modules at a site, beyond 16, would require a second EoN device.

17. What maintenance and maintenance periodicity is required (spec notes low maintenance) on a 48 VDC module to confirm performance and achieve full life cycle?

There are no maintainable parts. Cycle testing should be performed occasionally (once a year or less) to confirm functionality. Capacity degradation over time is less than ½ % per year.

18. Please confirm whether physical or electrical inspections are or are not required and why.

Whether they are in use or in storage, there is no physical or electrical inspections required. Due to self-discharge of about 2% per month when in storage, they should be tested and charged approximately every 36 months. The other reason to test installed supercaps is to confirm the charge controller is operating as expected.

19. What PPE is required?

Under normal conditions none. 48VDC is below the NEC electrocution risk standard. There is no off-gassing emissions from Supercaps.

20. What tools and test equipment is required?

Terminal types vary. If Amphenol connectors are used, no wrenches are needed. If bolt-type terminals are used, 10mm wrench would be needed to remove cables from terminals. Testing can be done with a typical voltmeter and DC clamp-on Amp meter. A laser thermometer can be useful for testing under load for loose connections and terminal temperature.

21. What installation, operation and maintenance manuals are available for a 48 VDC module?

These will be provided with delivery.

21. What installation, operation and maintenance manuals are available for a 48 VDC module?

These will be provided with delivery.

22. Please confirm whether an installation, operation and maintenance manual is available for review.

Yes they are available.

23. What training is available for a 48 VDC module?

Training is pretty simple and typically covered in the operation manual. But, if remote monitoring is employed we may need to arrange something specific for that purpose.

24. What technical support is available for a 48 VDC module?

48hr turn around for any questions should they need to go to the manufacturer. 24hr for any questions we can support locally.

25. What are the LRUs and what part replacement support is available for a 48 VDC module?

Modules connected in parallel can be swapped without shutdown of the system taking appropriate steps to avoid a short circuit of terminal wires. Warranty replacement 10-years.

26. Please confirm whether the module is the LRU. Please confirm lead-time on the LRU.

The module is the Line Replaceable Unit, the BMS is internal and cannot be swapped without opening up the module. We will stock these with a lead-time for LRU of approx. two weeks. We suggest you stock spares. All this said, a system with multiple modules will incur some overall capacity reduction if one module fails, but because they are parallel connected the system will continue to operate.

27. What warranty is offered on a 48 VDC module?

10 years.

28. Please confirm if the warranty document is available for review. Please confirm if warranty is full or prorated. Please confirm what conditions, scenarios void the warranty

We will provide the Warranty Document along with the Installation manuals, etc. The warranty is 10-years, conditional but not prorated.

29. How many years has the 48 VDC module supported customers in the field?

< 5 years. New Product. As with most Supercapacitor Energy Storage solutions, the technology has been around for < 10 years, even though capacitors in general have been in use for over 100 years.

30. Please confirm whether the super cap is UL listed.

Testing is underway. UL810A, UL9540A and UL1973.

31. Is the 48 VDC module compliant with the buy American act?

Not at this time. We are working to move manufacturing to the US, but that is a 2-year effort to complete.

32. Please confirm whether you can share approximate pricing (equipment only) for two four foot SuperCap racks (100 amps at +48 VDC for 36 hours) that could be utilized to supplement DC BUS rectifier operation when commercial power is not available.

Small orders are being sold at $850/kWh for the modules. Larger orders, would incur a discount, TBD. So for a 24 – 48VDC, 7.46kWh module solution, the price would be approximately $152,184, + three approx. eight module racks of $1,500/rack, plus shipping and taxes, if any. Volume price is subject to further discussion.

33. It is noted that the Supercapacitors are not yet made in America and there is a 2-year effort under way to change that. Do the Supercapacitor modules have (foreign) firmware for control capable of shutting the unit down? If so, does PowerForma have a mitigation plan?

No. The simplest means to mitigate any external control concern is to not install Wi-Fi or RS485 communication cables to the modules. We have many modules in operation that rely solely on the module displays for status, including voltage, current, SoC and Temperature, etc. We have an option to provide local view only through a PC that is not connected to your LAN and has no external access. These modules do not support remote control functionality, so external control is not possible. All control decisions are driven through settings in the rectifier/inverter. Remote monitoring software (EoN mentioned previously) is available from Supercap Energy which is US-made by us.

34. It is noted that the Supercapacitors do not output toxic gases. Is this the case when they are operating in a compromised condition immediately before or after a failure? For example, batteries can output acid mist when they are not operating optimally but it certainly is not a normal output.

The BMS within the module will disconnect and stop module operation if limits are reached and an abnormal condition is identified. This includes temperature, voltage, and current abnormalities (outside of operating range in the spec sheet). Installation should always include properly setting the rectifier/inverter as the primary limiter per the module installation manual. Lead Acid batteries do not contain a BMS so the primary point of control to maintain them within their operating range is the rectifier/inverter. The supercap BMS provides a second layer of control and safety beyond the rectifier settings. The BMS provides alarm and protection functions, and our cells are the safest technology available today, our system won’t output any gases during operation or even if it were to fail.

35. In normal operating conditions, do the Supercapacitors release any gases (such as H2) that are not toxic but still require to be managed? The Supercapacitors are rated for operation in relatively extreme environments. Do they derate as temperature changes within their operational rangen. For example, lead-acid batteries lose capacity in lower temperatures, but they can be compensated to a point (upsized). Likewise, they lose expected operational life in high temperatures but can be compensated to a point (replaced early). Is it the same for the Supercapacitors? If so, we will need to alert users to how to compensate.

Somewhat. See Figure 1 below for example.

There are two conditions to discuss here. 1) daily temp swings if outside plant. 2) Average ambient temperature that the module operates in. Regarding #1. The BMS automatically compensates for daily variation in temperature that may have a minor impact on maximum voltage. In other words, it self-adjusts to avoid an unintentional over voltage event. Regarding #2. Cycle Life is not affected by lower temperature, unless the low temperature charging is a regular occurrence, in which case cycle life can be slightly affected. To mitigate this under cold conditions we suggest recharging a) when temperatures are closer to normal, b) prior to SoC reaching 10% if possible and c) at a lower rate of charge below 0.5 C-rate.
The forecast cycle life, depending on the cell type, is 10,000 or 20,000 full discharge/charge cycles. I believe the modules we’re recommending for your applications are 20,000 life-cycle cells. Capacity somewhat diminishes at temperatures below freezing and the module will stop charge/discharge if it is extremely low, i.e., below -20 degrees C. (If there is a need for a -40°C solution, we have a different 50,000 cycle life cell that can achieve that, but it’s much more expensive). If you think the ambient temperature of a site will linger near 0°C, we should discuss adding a bit more energy storage in the way of additional module(s). High temperature does affect cycle life if it’s a continually high ambient temperature. Given the long cycle-life of these supercapacitors, any lost cycles due to temperature are probably not meaningful as other electronic components do not have the same projected life and may need replacing prior to the cells themselves reaching end of life. A likely operational expectation is 20 years.

Figure 1 – Cell delivered Ah Capacity at various temperatures

 

36. It is noted that training is covered in the operation manual. It was suggested that training beyond the manual would be needed. In addition to introducing users to the technology (in an existing DCBUS) they also need to know how to read and interpret alarms, how to compensate for temperature, and how to do all other possible maintenance. Is PowerForma able to provide additional training?

Yes

37. It is noted that onboard monitoring is limited to 16. Is there an update on how the 16 modules will be monitored for our application?

Today’s remote monitoring product can monitor up to 16 modules connected in series via RJ45 cable using Modbus and/or product specific software. The number of modules that can conceivably be connected in parallel can be higher, but additional monitoring would have to be installed, i.e., groups of up to16. Modules can operate without any monitoring and the individual module displays used to check their operating status (Voltage, Current, State of Charge, Temperature, cycles to date).

38. It is noted that cycle testing should be performed appx once per year. This sounds like a capacity test similar perhaps to what we do on batteries at about the same frequency. We need the curves and a test procedure to do the cycling. Folks will need training for this.

Curves and test procedures will be supplied with products. You may determine that annual cycle testing is excessive, and that schedule could be relaxed to every 2-3 years depending on the application.

39. It is noted that installed Supercapacitors should be tested to confirm the controller is operating correctly. The frequency and details of this check are not clear. Training will be needed.

This is more a test that the rectifier/inverter is properly calibrated for the supercaps. Generally, that setting is similar to a lithium-ion battery, but we do provide a wider Depth of Discharge range and the ability to maintain the supercaps closer to 100% SoC, See response to related question #13 below. So, at installation we’ll provide assistance in making sure the system is optimized for the application and site. This is an initial setup requirement and should be completed within the first few days of operation depending on load and how long a “natural” cycle can be executed and recharged. Once properly set up, additional testing should not be required going forward. Setup procedures are provided in the installation manual that should be followed.

40. Do Supercapacitors have the need to confirm connection integrity? Batteries do this check quarterly (and retighten annually). If so, training and torque parameters are needed.

At the time of a scheduled cycle test, it would be advisable to check connections. Supercaps do not heat up under load to any significant amount, so temperature caused loosening of the terminal bolts is not a factor. It really depends on the type of connector used. Bolt type should be checked. Amphenol snap-on connectors require no maintenance and are common on most of our new installations in telecom and cable industries. For bolt-type installations the installation manual provides recommended torque settings.

41. It is noted that the installation manual and warrantee documentation will be provided. Please provide documentation for review if available.

These can be provided.

42. The cornerstone of battery maintenance is to ensure operational reliability. Problem cells, overuse, non-ideal environments, and other factors can cause premature failure which take a toll and must be accounted for by the user (via testing). Said maintenance has little to do with extending the battery life but rather allows the user to plan replacement before a failure. In general, we know that capacitors can fail unexpectedly. Do these capacitors have known test points that can allow users to discern their health on a periodic basis? For example, trending voltage, trending internal resistance, confirming capacity. Are the capacitors expected to become more prone to unexpected failure after they age? Can non-ideal conditions cause premature aging or other degradation?

Your in-house service technician or end user can read all the supercap information through an attached computer, (See response to related question #1 above) it will show the cells voltage conditions, system health, alarm and protection records etc. With this information, you can determine the supercap aging condition and make decision to replace or not.

43. It is noted that should a BMS or capacitor fail, it is a parallel leg and can be swapped for a working replacement. If swapping like this occurs it will effectively mix older and newer modules. Will they operate well together? Is it expected that newer capacitors will remain interchangeable with older ones? Will newer modules degrade more quickly when placed with older ones? Will there come a time that the user should replace the entire system? How should the user discern this?

Ideally, it is better to use same shipping lot modules with similar ESR to replace the failure modules. If no spare modules of the same type are available, then new modules of similar specifications can be used. There is no problem when mixing similar spec modules, because the BMS not only protects the system, but also provides balancing among the modules thereby protecting new modules from early degradation. There will be a time for full replacement and regular cycle testing can help determine that time. Temperature, to some degree and C-rate do affect when full replacement may be required. Refer to the response to question #15 below for more information.

44. Is there a maximum charge current that staying below would maximize life?

Yes, below 0.5C charge current would maximize life. Below 100A charge/discharge, dependin on the module is optimal.

45. Is it safe to maintain the Supercap at 95% SoC? What would be the life impact of maintaining at 100%? To help respond, their typical cycling does not exceed 100/year.

While safe at 95%, for optimal life of SCEM 48V7400-E, suggest setting float at 57.4VDC, or approx. 97% of max 58.8VDC. There are additional variables that determine cycle life degradation other than 100% charge, such as operating temperatures, DoD and rate of charge/discharge. Practically speaking once Bulk charge is completed to near max charge of 58VDC, there is a natural drop off thereafter as individual cells internally balance, so 100% cannot actually be maintained… perhaps 97% is possible, which is considered in the kWh rating. Figure 2 below is a typical 48VDC Charge/Discharge curve. We recommend that Absorption be set to a minimum time and at the same voltage as Bulk Charge. Equalize charge should be disabled. Float as stated above.

46. Is a full life cycle curve available for any of the 24V, 36V, or 48V modules?

No. Life cycle tests are only done at the cell level. Module cycle life testing is an expensive and time consuming effort making it impractical to perform. See Figure 3 – 30Ah cell test chart below. (Note: this is for a 10,000 cycle life cell. The 20,000 cycle life cell will is approx. double what is shown here with same final life retention, approx. 78%).

47. I would like to know the degradation of the supercap over life (% capacity loss) and is it linear?

There are other factors, particularly rate of discharge/charge that affect degradation and cycle life. Looking at the test results in Figure 3 below, you can see the cycle life at 1 C-rate and exceeds 8,000 times at 100% DoD, if C-rate is under 0.5C and 90% DoD, the cycle life goes up to 15,000 times. Cycle life is linear. Once again, this example is for a 10,000 cycle life cell. A 20,000 cycle life cell will achieve approx. 30k cycles if operated under 0.5 C-rate.

48. Temp compensation is a concern. Is the same max voltage setting used at 0 degrees C as at +50 degrees C. In other words, does a temperature swing from night to day represent a risk of over voltage in the module? Does the BMS automatically compensate for temperature? Please provide setting recommendations.

Temperature compensation is an automatic BMS function. Max voltage setting are same used at 0°C as at +50°C. the cut off discharge voltage would be lower if discharge under 0°C. Settings (in the rectifier/inverter) should follow spec sheet and installation manual recommendations based on 25°C. BMS will compensate around those settings for actual temperature.

49. What is the maximum Current rating for the Amphenol terminal connectors? Are they rated for the maximum continuous current of the module?

Rated for max continuous and peak. The Amphenol connectors are designed for 200A, 2 AWG, on a module rated for continuous charging current of 100A and max. instantaneous current of 180A, the connectors are within tolerances.

50. The intended location offers the possibility to connect to 150KVac, 10KVac and 480Vac. Would all of these be proper connection voltage for such a storage system? Or is one voltage beneficial (considering the use cases)?

Typically, we see the Energy Storage connected at between 700 and 1,100VDC nominal to an appropriate three-phase 480VAC PCS. A step-up transformer is needed to bring system voltage up to the necessary VAC grid connection level. Pictured here is a small demonstration system we installed in Tampa Florida for the utility there. In this system, the DC voltage is 700 nominal and the AC voltage is 480 3-phase connected to the building service. Building service is connected at 12.5kV to the distribution grid. The intent here is to arbitrage power every evening. Moving solar generation from daytime to evening. The right side of this cabinet contains the PowerForma energy storage. The left contains a 40kVA PCS and a display screen for customer viewing of data. So, this example is 40kVA/150kWh. We are building full system in 20’ and 40’ containers of approx. 1.5MWh and 3.0MWh respectively. Their discharge rate is a function of the PCS used.

51. How much heat would be released and at what temperature during a typical charge and discharge process at 50MW from a 200MWh storage solution?

Unlike lithium and other redox reaction chemical batteries, the Supercap cells themselves do not release significant heat, however their power aggregation through Mosfet Transistors within the modules and the PCS inverters do. A 200MWh solution would be made up of approx. 19,600 – 10.75kWh Supercap modules and 400 – 125kVA rack mounted PCS assembled in approx. 70 – 40 foot containers. In a 50MW/200MWh system, each of the 19,600 modules is releasing 2.55kW,operating at about 1,000VDC. Current through each Supercap module is thus a relatively small approx. 2.55A (2,550W/1,000V). This is a C-rate of about 0.25 which is consistent with the 50MW/200MWh relationship. At this discharge rate, the module heat is insignificant. The PCS would be operating at full power (125kVA in this example) and would likely be operating at 40-50 degrees C, requiring HVAC management in the container, on most days. These products have a 95% efficiency rate, so the heat, as measured as a the heat loss in efficiency is small.

52. We want to utilize this heat by injecting it into a city heating grid. Would this be possible from your point of view (realization up until the heat exchanger with the heating net)?

Sure, you could move air through the containers, similar to a heat exchanger, and extract this heat for your purposes. However, it is always preferable to have high efficiency energy transfer from the batteries electrically than having to deal with the heat generated from losses. Whether it is using HVAC to cool the energy storage or capturing that heat for other purposes like passive building heat, converting it to electricity rather than heat is easier to apply elsewhere to do useful work (heating, motors, lights, etc).