In late 2023, California-based EV manufacturer Motiv Power Systems delivered five electric step vans to Shasta Linen Supply, which is headquartered in Sacramento.
Shasta has retrofitted its existing business infrastructure to support the Motiv trucks. The new trucks, operating on local routes in the Sacramento and San Joaquin valleys, now make up half of Shasta’s fleet. This puts the company well ahead of the state’s Advanced Clean Fleets regulation that requires fleets to be 50% electric by 2031.
“Given the sheer weight of linens, building an electric truck that can handle the payload is an industry-wide challenge. Motiv rose to that challenge,” said Jim Castalez, founder and Chief Technology and Revenue Officer of Motiv Power Systems.
The demand for electric vehicles continues to increase, with EV sales growing faster than any other major category of automobile. According to an article in Forbes, 2023 was the first time more than 1 million EVs were sold in the U.S. in one calendar year, reaching between 1.3 million and 1.4 million cars by year end.
Thermal management is a critical requirement for the safety and performance of EVs. Poor thermal management may result in thermal runaway events, creating a hazardous fire condition. Also, poor thermal management reduces the electronic components’ efficiency because excessive heat increases electrical resistance and lowers the power and energy of the EV. It is, therefore, important to remove heat from battery and powertrain components efficiently.
What is Battery Safety?
Generally, battery safety encompasses protecting the battery system from several adverse circumstances – electrical, thermal and environmental conditions. The purpose behind battery safety is to provide a safe and reliable battery pack operation in all situations, as well as minimize the losses in case of hazardous events such as battery thermal runaway.
Safety Hazards
Electrical safety: With high voltage components in an assembled battery pack, it becomes highly important to keep those high voltage components isolated. Otherwise, an arcing event or electrical short can compromise battery life and even worse can lead to thermal runaway and eventual battery fire. Such electrical isolation can be incorporated in a battery pack with use of dielectric coatings, gap fillers and seals.
Thermal hazards: The Li-ion batteries operate most efficiently within a tight temperature range of 20 to 35 °C. Due to electrochemical reactions within a battery while it is charging or discharging, a lot of heat is generated. If the heat dissipation is not managed property, that can compromise battery performance and in worst case, lead to thermal runaway. A well-engineered active temperature control system allows for battery pack to operate in optimum temperature range. The efficient temperature control is provided by thermally conductive and electrically isolating interface materials. These are applied in between heat source (battery) and heat sink (cooling plate/ribbon).
Environmental isolation: The high-voltage batteries can be sensitive to moisture. The individual battery packaging allows for moisture isolation. However, redundant solutions must be incorporated in battery pack design for additional safety against moisture. Structural adhesives, extruded seals, molded seals, and dispensed seals can be used to seal battery modules and packs. Additionally, the batteries contain toxic components, such as fluorinated electrolytes and transitional metals which can contaminate water supplies and ecosystems. The seals provide enclosure for containing these inside the pack until it can be disposed of adequately.
Battery Thermal Safety
The safe operating temperature range for batteries is defined as between -40 °C (-104 °F) and 80 °C (176 °F). The best performance is found between 20 °C (68 °F) and 35 °C (95 °F). Operating at the extreme temperatures is dangerous and can cause a fire.
Causes of Battery Thermal Runaway
Thermal Runaway is described as an uncontrolled increase in cell temperature caused by exothermic reactions inside the cell.
Thermal Runaway Propagation (TRP) is the sequential occurrence of thermal runaway within a battery pack triggered by thermal runaway of a cell in that battery pack.
Source: Liu et al., Science Advances, 2018;4: eaas9820
The scientific consensus on the thermal runaway of Li-ion batteries is still developing. However, there is a still wealth of literature to provide a broad understanding of the process happening inside a cell that leads to its thermal runaway.
The onset of overheating is most likely caused by a manufacturing defect that leads to internal short and a consequent current surge. Such internal short can also result from cell crush, Li dendrite formation, overcharge/discharge, or external heat. The current surge produces spike in temperature. If not dissipated quickly, this results in separator melt, SEI layer decomposes, and anode is exposed. As the temperature increases further, cathode decomposes, and oxygen is released from cathode lattice structure. A self-sustaining fire cycle is formed with fuel in form of electrolyte, oxygen and heat. At an onset-temperature, the cell blasts into a fire and if this heat, fire and gases are not managed properly, this can cascade into thermal runaway of neighboring cells.
Regulatory Landscape on Thermal Propagation
Regulations on battery safety have been advancing throughout the world in last decade. UN EVS-GTR No. 20 Phase I was enacted in 2018 that among other battery safety protocols, enacts a 5 min warning to passenger after thermal runaway of first battery is detected. Since then, the regulation has been adopted in Europe and USA. China enacted GB 38031 in 2020 that adopted the same 5 min warning. India enforced regulations around battery safety through their AIS 038/156 enactment in 2021. It describes various safety test for batteries and battery pack. However, no 5 min warning is required.
Currently, US, Europe, and Japan are working towards Phase II of UN-EV GTR No 20, which is anticipated to come into effect before end of this decade. The expectations are the regulations will become more stringent around battery safety, with possibility of introducing no thermal runaway propagation.
Operational and Thermal Runaway Safety Solutions
To protect the EV battery, Parker Lord has taken several steps to reduce the threat of thermal runaway. These solutions can be seen in the assembly around the battery.
1 & 2 (Coatings):Coatings for batteries are available as a dielectric epoxy coating or ultra-violet (UV) cure dielectric coating. Application areas for coatings include the cooling plate, battery pack enclosure, prismatic cell can enclosure and cylindrical cell can enclosure. Higher energy density requires powerful high-voltage batteries. Higher voltage therefore requires greater precaution in preventing arcing between electrical components and a need for increased battery safety. One major area of focus to achieve this is to improve electrical isolation by using dielectric materials, such as Parker Lord’s Sipiol UV cure coating and heat cure epoxy coating.
3, 4 & 5 (Thermal Management Materials): The most used thermal management materials are gap fillers, thermally conductive adhesives, as well as potting and encapsulants. These materials are used on the cell-to-cooling plate, module-to-cooling plate, intra-cell potting, and enclosure potting. Parker Lord’s CoolTherm® thermal management portfolio is recognized for its reliability and custom solutions for use in electric vehicles, energy storage systems, motors and other power electronics. These solutions increase performance, reliability and safety while delivering tailored products to manage the heat and increased power density in electric vehicles.
6 (Sealants & Adhesives): Structural adhesives and sealants for thermal management include the use of non-reworkable adhesives as well as reworkable sealants. They are used for enclosure bonding and sealing as well as module bonding and sealing. Parker Lord’s adhesives provide a structural bond and reduce the amount of mechanical fixturing required. They also allow greater design flexibility and the ability to bond dissimilar substrates. These structural adhesives can provide a structural or non-structural seal for battery modules and packs to keep battery cells protected from the elements and improve safety.
Your Partner in Innovation
Innovations in materials and technologies play a crucial role in advancing the reliability, efficiency and safety of electrified transportation. Thanks to their market leading safety solutions, Parker Lord works together with their customers to propel the transition toward sustainable and electrified transportation ecosystem.
If you have questions, reach out to Parker Lord today.
The “house of the future” is a perennial American theme—from the Homes of Tomorrow Exhibition at the 1933 World’s Fair to The Jetsons, futurists have predicted a proliferation of labor-saving devices and home entertainment options. Nowadays, the focus is increasingly on the energy that these nifty gadgets require. The home of the future that we envision today is an intelligent home, and much of the intelligence has to do with optimizing energy consumption—shifting demand to times when energy is cheaper and/or cleaner.
A smart home can manage energy consumption across one or more EV chargers, possibly solar panels and/or battery storage, and thirsty appliances such as climate control systems and refrigerators.
Leviton is perhaps best known to consumers for its stylish light switches and dimmers, but the 118-year-old company makes a vast array of electrical equipment, and it has long been interested in integrated “whole-home” solutions. Leviton has also been in the EVSE space for a little over 12 years, and has produced chargers for a couple of major auto manufacturers, so it’s no surprise that the company is a leading proponent of the EV-enabled smart home.
Charged spoke with Andrew Taddoni, Leviton’s Director of Business Development and Product Management for EVSE.
Charged: It looks like Leviton is concentrating on Level 2 chargers at the moment.
Andrew Taddoni: We are heavily focused on Level 2, and the reason is that it’s really within Leviton’s sweet spot of the contractors and customers that we deal with globally, and Level 2 is the most common charging level in the North American market. Leviton is well known and respected in the home market—everyone knows our switches. In the US alone, it’s estimated that over 75% of homes have at least one Leviton device. People know the Leviton name—they see us in the Home Depots and the Amazons of the world.
In the US alone, it’s estimated that over 75% of homes have at least one Leviton device.
And then we have relationships with a lot of electrical contractors that serve both residential and commercial public use settings—they’re doing installs in commercial buildings, garages, parking lots, hospitality and healthcare.
Charged: Are you equally focused on the residential, commercial and public charging markets?
Andrew Taddoni: On the residential side, we have a full offering that services the single-family home as well as multiple dwelling units and communities. Our EV Series Smart Home Charger is compatible with the My Leviton app, allowing for a whole-home smart ecosystem solution. A big goal for us is to be the number-one player in the residential charging world. This goes hand-in-hand with what we do in residential settings already. A lot of people know us, a lot of contractors know us, and this idea of building on smart technology and systems that are inside your home is becoming more and more popular. Our customers don’t just want switches anymore. They want these switches to have schedules and they want to control them. They don’t just want an EV charger—they want a charger that they can control and that can send data to their smartphones in real time.
We are also very focused on the commercial market. We service a lot of hospitals—they have a lot of people coming to them that need chargers. In the hospitality world, the Level 2 play is more about convenience: “We have charging at our establishment. Come in, eat, shop, charge for a couple hours on us.” Again, because we’re already in there, we’re already talking to these contractors and customers. That specific solution is our new EV Series Pro, which is a public charging solution that allows the site host to collect analytics and collect revenue if desired. For that we have a partnership with AmpUp, an EV charging management company, which takes care of the software side of things.
In the hospitality world, the Level 2 play is more about convenience: “We have charging at our establishment. Come in, eat, shop, charge for a couple hours on us.”
The focus is on two situations: somebody says, “I want the ability to collect analytics, have data at my fingertips and understand who’s charging, when they’re charging, and the energy usage.” That’s one piece of the pie. The other big piece is revenue collecting: “I want to be able to bill at the charger, and make a certain amount of money every time people charge.” Our EV Series Pro enables any commercial public use property to know what’s going on at the site, and allows the site host to control all of those settings.
The other big market that the EV Series Pro plays a role in, and that’s really starting to take off, is the fleet market. Big distributors are starting to get EVs, and they need the ability to charge on-site. Amazon is the best example—they have a partnership with Rivian where they’re using electric trucks for deliveries. You have a ton of distributors that want to do the same thing, so that’s another big focus for us.
Charged: As far as sales channels, automakers are partnering with equipment manufacturers like yourself. They want to sell a charger with the car. There are also installers that are buying hardware from various manufacturers. Then I guess there’s a certain amount of selling directly to fleets and end users. Through which of those sales channels are you selling most of your hardware?
Andrew Taddoni: I would say it’s a mix, based on the application. On the residential side, Amazon and Home Depot are big avenues for us. There are a lot of homeowners that are buying these chargers themselves from these retailers.
The automakers, a lot of them only offer Level 1 chargers, and leave the homeowner to do their research, buy a Level 2 unit themselves, and then hire an electrician to come and install it. So that’s a big focus for us, not just through retail stores and online, but also, we have a lot of electrical contractors that are getting calls to do installations. That’s a big, big piece of the market.
I went through the process of buying a plug-in hybrid myself, and aside from startups like Lucid and Rivian, and Tesla of course, I don’t feel that they are focused on actually selling the charger. I think they’re more focused on selling the cars. Some are doing a better job than others, but a lot of customers need education, not just on the product side, but on the installation side in their homes, which we’re trying to give at Leviton.
We’re also spending a lot of time with third-party companies that are selling turnkey solutions. I think we need to strategically work with everyone right now, because the opportunities are coming from all different areas and directions.
Charged: At the other end of the spectrum from the EV newbie who just wants to know how to plug it in, what do you have for the nerds who want to keep track of how much energy they’re using and how much it costs?
Andrew Taddoni: With our whole-home smart solution connected via the My Leviton app, we offer the Leviton Load Center, which includes a smart panel; the core of smart devices and switches controlled by WiFi; and now our EV Series Smart Home. With the Leviton Load Center, there are smart breakers that will tie right to our charger, and every time you plug in, it will tell you your kilowatt-per-hour usage. This is going to continue to evolve over time, but I have the My Leviton ecosystem, and I can see in real time every day what my energy usage is per charge.
I have a plug-in hybrid, so I only have 45 miles of true electric driving, but I plugged in every single day at home for a month, to understand what my electrical bill would increase by, and it was 32 bucks. I knew the exact number down to the penny.
Charged: Your smart panel, does that require replacing the whole panel, or can it be retrofitted to the existing panel?
Andrew Taddoni: Right now, it involves replacing the whole panel. It’s a whole new system, but easier to install. Once the Leviton Load Center is installed, homeowners can snap smart breakers in and out, rather than wiring each breaker. It is a very, very cool system, but it’s an investment.
What we’re seeing more often than not is two scenarios. The customer installs a charger in a residential setting, realizes there’s not enough room in the panel, and the contractor says, you can either upgrade your current panel or put in a sub-panel, but you’re spending a lot more money. Some of the contractors do know about devices that allow you to do some sort of load management or load shedding in the home, which is becoming more and more popular. Leviton is looking into adding these types of products to our offering.
Charged: How much does the smart panel cost?
Andrew Taddoni: It depends. If you go with the panel itself, regular non-networked, it’s comparable to all the big names that are out there. If you put a level of smartness in it, it depends how many breakers you want to make smart.
Smart switches can be expensive compared to standard lighting controls, but as I always tell people, every single switch in their homes does not need to be smart. You probably have 10% of the switches or less in your home that actually need to be connected. It’s the same situation with the panel. You really want certain loads to be monitored—your EV charger, your refrigerator, your heating system, stuff like that. Maybe four or five of the breakers, so it’s not a huge expense. The bigger piece is the electrical contractor’s charge to install a new panel—that can get pricey.
Leviton’s new 50 A heavy-duty EV charging receptacle
Charged: So, if someone’s going to have to install a new panel anyway, they might not be spending much more to go with a smart panel.
Andrew Taddoni: Correct. As long as you do it right. A couple of those breakers, you make smart. For the rest of them, we have non-networked breakers that are in line with everyone else’s, which can be switched as needed.
Charged: You make a 50-amp heavy-duty receptacle that appears to be specifically designed for an EV charger—it’s even got a little picture of an EV on it. Now, the average homeowner probably doesn’t see any difference from one receptacle to another, but I’ve been told by EVSE installers that the cheap receptacles at the big-box stores aren’t suitable for the sustained high power levels and the frequent plugging and unplugging of a portable EV charger.
Andrew Taddoni: The residential team at Leviton spent a lot of time redesigning the new 14-50 NEMA receptacle for the reasons that you just said.
Say somebody has had a receptacle in their garage for a long time and they come home with a plug-in charger, and say, “Let me just plug it in and I’m good to go.” But they don’t know who installed that receptacle, they don’t know what it’s rated for. And very few of them, other than our new receptacle, are rated to pull power for four to six hours or more. If I start my dryer, in 50 minutes it’s done and I’m not going to do it again for another few days. But charging an EV might mean pulling current for four to six hours every day. Wouldn’t you want a product that has been tested? The torque requirements are way more robust. Everything on the inside of that product is built to survive regular charging four to six hours at a time or more to ensure that there are no issues from a safety standpoint.
Very few of them, other than our new receptacle, are rated to pull power for four to six hours or more. If I start my dryer, in 50 minutes it’s done and I’m not going to do it again for another few days. But charging an EV might mean pulling current for four to six hours every day.
Leviton recently launched a 40-amp plug-in version of our EV Series Smart Home charger as well, so this and the receptacle bundle nicely together. If you prefer a hard-wired unit, we have 32-amp, 48-amp, and even 80-amp models for the home. The homeowner can choose what’s most convenient for them.
Charged: It seems like every day I read about a new company getting into the game, some of them startups that make nothing but EV chargers. You’re at the other end of the spectrum—you make loads of different electronic devices. Does that give you a competitive advantage over these other companies?
Andrew Taddoni: Yeah, I think it gives us a huge advantage. If there’s a slowdown in the overall market, some of these startups, are they going to face challenges? Customers need the right service and support. Leviton has been doing it for 118 years, and we don’t only rely on our EV charger sales. We have a whole infrastructure of products that supports the overall company.
Here’s what we’re hearing from site hosts and electrical contractors: “I want to come to Leviton because I’ve dealt with you in the past and I know the name.” It’s been a really strong message for us to say: “Yes, we will be here to support you. We’re not going anywhere in the EV charging world—we’re continuing to invest in it.”
Also, we’ve been in the manufacturing world for quite some time, so we understand the dos and don’ts, the pressure points, etc. We have an army of people, not just on the product side, but design manufacturers, a full marketing team, a very large customer service team, and a tech team that will take care of the products that are installed.
Charged: Do you have some other new products coming out that you’d like to tell us about?
Andrew Taddoni: Now that Tesla’s NACS connector is becoming more common, we’re going to be in this world of adapters for a little bit, so we have an NACS adapter that will easily pop right onto the front of our J1772 connectors, and it will make sure that our chargers can charge any of the Tesla models, or any future cars that are going to require a NACS port. It’s going to take some time for automotive manufacturers to flush through their inventory and put this new NACS port on there, but it is something that’s going to happen, and we have an easy, convenient solution.
And then we’re coming out with a dual-port unit for the commercial, public use customer. We have a single-port charger today—that’s our EV Series Pro with AmpUp software. Our dual-port 48-amp model allows multiple cars to charge at the same time if you don’t want to install two on the same pedestal. We’re giving options to people. “What is your situation? What would you like to do? We’ll have a solution for you.”
This article first appeared in Issue 67: January-March 2024 – Subscribe now.
South Korean EV battery manufacturer SK On, a subsidiary of SK Innovation, has signed a memorandum of understanding with the Italian luxury sports carmaker Ferrari to reinforce their partnership and innovate cell technology.
The agreement allows the parties to share their experience in various fields to improve their technical collaboration and share insights. The new relationship should enable SK On and Ferrari to discover new cell technology solutions. SK On, currently the only battery supplier to Ferrari, has been providing battery cells for Ferrari’s SF90 Stradale and SF90 Spider models since 2019. SK On’s batteries have been also powering the 296 GTB and the 296GTS PHEVs that were launched in 2021 and in 2022, respectively.
“Combining expertise and technologies from the two companies, we expect to provide customers with new experiences and values,” said Lee Seok-hee, CEO of SK On.
Many people feel a need for long-range batteries when they buy electric vehicles, and that actually goes for new buyers as well as repeat buyers. I have to admit that I have a hard time understanding it unless you’re an encyclopedia salesman (not sure if those still exist) or go … [continued]
UK automotive testing technology company AB Dynamics has announced its acquisition of US dynamometer-based testing services provider Venshure Test Services (VTS).
The maximum consideration payable for VTS, which is being acquired from its two shareholders, is $30 million. The initial cash consideration is $15 million.
VTS is focused on developing and deploying EVs for US automotive OEMs. It comprises facilities that offer such testing services as mileage accumulation and assessment of EV powertrain and battery performance in extreme climatic conditions. Its standardized procedures are used to validate EV battery energy consumption and range testing by producing SAE J1634 quality data.
The acquisition is intended to enable AB Dynamics to expand its testing capabilities, and to complement its California-based track testing services business with laboratory-based testing.
“The acquisition expands both our capability and geographic coverage in the important and growing field of EV battery and powertrain performance evaluation,” said AB Dynamics CEO Dr. James Routh.
The poor reliability of public EV chargers is an industry-wide scandal. A year ago, when legacy automakers started adopting Tesla’s NACS charging system, many seemed to assume that this would soon solve all the problems. More sober observers told us that one of the main reasons Tesla’s Superchargers have been so reliable is that vehicles, chargers and network were all controlled by a single company—and that advantage was always going to disappear as soon as other brands’ EVs started using the Superchargers.
Here at Charged, we were also skeptical about the wisdom of granting so much power over the charging scene to any one company (especially one with a loose cannon at the helm). Those concerns were arguably validated this week when Tesla reportedly laid off its entire Supercharger team and threw the industry into turmoil.
It remains to be seen how the surprise move will affect Tesla and other industry players, but whatever ends up happening, Tesla’s NACS has morphed into SAE J3400, and it isn’t going away. Interoperability testing has been going on for months, and will continue. One of the companies at the center of this is EcoG, which provides an operating system that powers EV chargers from many different brands.
“Tesla might test its EVs with 5 to 10 charger types, but the broader challenge is much more complex.”
“Tesla is doing better because there you have this single entity controlling both the charger and the vehicle,” EcoG CEO Joerg Heuer told Charged in a recent interview (which took place before the latest Tesla news). “Most people look to the charger, but we also look to the vehicle. We provide a Reliability Index for vehicles, and we plan to publish the second edition sometime later this year.”
“Right now, we’re looking at a landscape with about 100 charging station manufacturers and a growing number of EV manufacturers,” said Heuer. “Tesla might test its EVs with 5 to 10 charger types, but the broader challenge is much more complex. To achieve a truly seamless charging experience for any EV driver, we’re tasked with ensuring that every electric car can use any charging station. Achieving this interoperability means testing over 500 different combinations of cars and chargers.”
“Achieving…interoperability means testing over 500 different combinations of cars and chargers.””
One thing that will hopefully facilitate interoperability over the coming years is the fact that NACS/J3400 is not radically different from CCS. “The plug is quite different, but all the processing behind it is quite similar,” Heuer explains. “That’s also the reason why in Europe they can easily use a CCS plug, and in US they have these adapters. Of course, in the foreground, it looks very different because the plug looks different. But in the background, the automation, the really complex stuff, that’s quite similar.”
“About two weeks after the announcement that Ford would adopt NACS, a customer of ours just added a Tesla cable to their CCS station, and the thing worked with a Tesla vehicle,” Heuer told us. “That’s the nice thing. It’s no longer this competition between CHAdeMO and CCS, which were really totally different systems. Compared to CHAdeMO, I would say 90% or 95% is really the same between CCS and NACS.”
Some find it ironic that in Europe, Tesla adopted the CCS plug, whereas in the US, vehicle OEMs and EVSE manufacturers are adopting the Tesla plug. Heuer explains that there are several reasons for that. “One reason is that in Europe, we have a three-phase AC system, so this would be a shortcoming of the Tesla plug because then they would only be able to charge one phase. In Europe, we would then be limited to three kilowatts in most countries, maybe maximum seven. That’s one physical aspect.”
A second difference between the North American and European markets is that the latter has developed in a less vertically-integrated way. “The networks started quite early with roaming and so on—it was not so dependent on what network or mobility service provider you contracted with. So the advantage Tesla had compared to the rest of the networks was not so significant.”
US battery materials producer 6K has confirmed that its cathode active material (CAM) will meet US government mandates for compliance with the Inflation Reduction Act (IRA) for both lithium iron phosphate (LFP) and nickel manganese cobalt (NMC) materials for EV batteries.
The company’s 6K Energy subsidiary is delivering large quantities of critical materials from its Battery Center of Excellence facility to customers for qualification. 6K’s UniMelt production system is capable of producing multiple lithium-ion battery materials, including NMC, LFP, lithium salts and alkaline battery CAM. It aims to deliver IRA-compliant CAM at a lower cost than materials exported from China.
The IRA offers additional tax credits for battery production in the US—as much as $35/kWh for the production of battery cells and an additional $10/kWh for battery module assembly. The Advanced Manufacturing Production Credit also offers a $7,500 tax incentive for EV battery production in the US—including 10% of the cost of critical mineral production and 10% of the cost of electrode active material production.
6K is currently building its flagship PlusCAM plant in Jackson, Tennessee, which is expected to start production in 2025. The plant will have the capacity to produce 13,000 tons annually, of single-crystal NMC811 and two LFP variants: a direct replacement for LFP made in China and a new spherical option for electrode construction, which the company says is effective for delivery of powder when using a dry coating process.
“During the past year, we’ve witnessed a transformation in the battery industry like never before. Targets for domestic production of batteries and battery material were once just aspirational goals and are now being mandated by the government with the introduction of the Inflation Reduction Act,” said Sam Trinch, President of 6K Energy.
Pacific Power Source, a global provider of AC and DC power testing solutions, has announced a new Regenerative product line of bidirectional sources and loads.
The new products, including the All-in-1 AGX Regenerative AC/DC Source, 2-in-1 RGS Regenerative Grid Simulator and RLS Regenerative Load Simulator, emulate real-world power flows, and are designed for testing EV chargers, V2X hardware, Solar PV inverters, home energy storage systems and more.
Pacific says the new SmartRegen products offer greater than 90% energy efficiency and a high power density, with up to 21 kVA in a single 4U chassis. Modular by design, these rack-mountable components can scale up to 168 kVA of power in a single 19-inch cabinet, and can be paralleled up to 252 kvA to meet future requirements. The voltage ranges cover 350 VLN/606 VLL in AC mode or ±500 VDC in DC mode with exceptionally high AC current capability.
The AGX Series Regenerative 4 Quadrant AC/DC Source is an all-in-one testing solution designed to address a wide range of test applications and markets. It can be used as a fully programmable AC/DC power source, current source and electronic load. It features AC, DC, and AC+DC output capability, and an extended frequency range up to 3,000 Hz.
The RGS Series Regenerative Grid Simulator is a next-generation 2-in-1 grid simulator designed for the testing and verification of all grid-tied applications. It’s designed to emulate almost any grid condition, and can test compliance with standards such as IEEE 1547, UL 1741, IEC 61000-3, IEC 61000-4 and more.
The RLS Series Regenerative Load Simulator is a four-quadrant AC and DC electronic load designed for testing any AC and DC load applications. The RLS features several AC and DC emulation modes, and provides flexible configurations of single, split and 3-phase operation, as well as steady-state or transient execution.
“Our new line of Regenerative test solutions offers the highest level of flexibility, performance and intelligence,” says Herman Vaneijkelenburg, Director of Marketing. “These test systems integrate a high-tech 4-quadrant design in silicon carbide (SiC) technology to support superior voltage range, current and power specifications. They are compact, powerful, versatile and easy to use. Our mission is to innovate how you test with smart power to make it simpler, safer, more productive, and sustainable.”
The holy grail for many EV owners is to obtain all of the energy needed for recharging from renewable energy sources, and while that’s difficult to justify on a purely economic basis if grid power is available, for those living off-grid it will be all but necessary to rely on renewable energy sources, as in this case running a fossil-fuel powered generator is the economically non-viable option (except on an occasional basis, as is its intended purpose).
An off-grid energy system basically consists of just four key components: 1) a battery to store energy; 2) one or more renewable energy sources (e.g. solar panels, wind turbines, hydroelectric turbines); 3) an appropriate DC-input charger for said source; and 4) a DC-to-AC inverter to power the house, EV charger, well pump, etc. from the battery. Since no renewable energy resource is available 100% of the time, you will probably need to incorporate a backup generator to supply an AC-input charger, but the good news is that this generator can be a lot smaller than if it were sized to power the house directly, because the inverter and storage battery will handle the peak power demands.
To properly size an off-grid energy system you need to know two key parameters: the peak power demanded by all of the loads that are likely to run concurrently; and the average daily energy consumption.
To properly size an off-grid energy system you need to know two key parameters: the peak power demanded by all of the loads that are likely to run concurrently; and the average daily energy consumption. The peak power demand sets the minimum size of the inverter, obviously, but it also influences the size of the battery (bigger batteries can supply more current, all else being equal), the size of the wiring, fuses/breakers, etc. The average energy consumption dictates pretty much everything else, from the number of solar panels or the swept area of the wind turbine to the storage battery capacity, and the power rating vs runtime of the backup generator, its attendant AC charger, etc.
A good way to get accurate values for these two parameters is with a whole-house energy monitor that uses current clamps on each incoming phase leg in the main breaker panel. If that isn’t an option (perhaps because the off-grid location isn’t yet up and running) then you can estimate the power demand with rules of thumb (e.g. assume that major appliances draw 80% of their breakers’ amperage ratings), appliance data labels, and even anecdotal evidence (e.g. the neighbor’s well draws 9 A at 240 VAC). As for estimating the average daily energy consumption, a typical value for us spoiled Americans is going to be in the range of 10-25 kWh per day for the first person in the house, and around another 2-5 kWh per day for each additional person.
Given that the size of the storage battery scales directly with this figure, it pays to determine it as precisely as possible rather than just relying on a thumb rule in an article you read in a magazine…ahem. Lastly, factor in the power rating of the EV charger, and if said EV will be charged when the renewable energy source isn’t producing—say, at night with a photovoltaic system—then you’ll also have to add the typical daily consumption of its battery capacity to that of the storage battery rating (in kWh, not Ah, since the two batteries will not be the same voltage unless the EV is a golf cart).
For estimating the average daily energy consumption, a typical value for us spoiled Americans is going to be in the range of 10-25 kWh per day for the first person in the house, and around another 2-5 kWh per day for each additional person.
The storage battery is what makes an off-grid energy system possible, so it is arguably the most important component, but it is also one with a fair amount of flexibility. The three key parameters to consider here—assuming a nominal 48 V rating—are the energy capacity in kWh, the current rating vs time (that is, how much current is allowed over timescales of seconds, minutes and hours and/or continuously, often given in C rather than amps) and the cycle life vs Depth of Discharge.
When it comes to the size of the storage battery, bigger is better, budget (and space) permitting, but a practical minimum is enough energy capacity to run everything as per usual for at least a full 24 hours, so that if the renewable source isn’t producing you don’t have to immediately fire up the generator (or, worse, go rushing off to get fuel for said generator…at night…in the rain). For those wanting more concrete numbers, I feel that 200 Ah (again, at 48 V nominal) is the bare minimum for a single person (speaking from experience here), while 400 Ah would allow for an almost carefree lifestyle (assuming there is sufficient renewable energy available to feed said battery).
The most common choices of battery type are lithium iron phosphate (aka LFP or LiFePO4), all of the other lithium-ion chemistries (including recycled batteries from junked EVs), and, finally, lead-acid. To reach the de facto standard of 48 V nominal (the actual voltage can go up to near 58 V, depending on battery chemistry) you can either wire four 12 V batteries in series, or the appropriate number of bare cells (typically 16 for LFP). There are also ready-made “whole-house” batteries available, such as Tesla’s Powerwall, but these are often aimed at grid-tied solar systems to be installed by licensed contractors, rather than DIYers, and they carry a correspondingly hefty price tag.
LFP is arguably the best all-around choice for off-grid systems, as it has a very high cycle life (in the range of 2,000 cycles at 100% DoD to 10,000 cycles or more if operated over the range of 80% State of Charge down to 20%), and it can tolerate high peak and continuous current draws of up to 4 C and 1 C, respectively, with negligible impact on longevity or energy capacity. There are two main choices of LFP batteries: those intended as drop-in replacements for lead-acid batteries; and bespoke 48 V batteries—often in convenient 10-inch rackmount cabinets—that are specifically designed for off-grid use. The former come in a wide range of Ah ratings (from 7-10 Ah for a computer UPS to 200+ Ah for off-grid systems) and have an internal BMS that protects against overcharge, overdischarge and overcurrent.
Lithium iron phosphate is arguably the best all-around battery type for off-grid systems, as it has a very high cycle life, and it can tolerate high peak and continuous current draws of up to 4 C and 1 C, respectively.
These typically lack the ability to communicate with other batteries in a series string (or other devices), nor do they come with any means of monitoring total charge in and out of the battery. The former shortcoming can be addressed with an external active balancer (aka charge equalizer) that automatically shuttles charge from the highest-voltage battery in the series string to the lowest until all are at the same voltage. The latter shortcoming is easily handled by an external battery monitor/coulomb counter (ideally with the ability to report such data to a remote display or smartphone via Ethernet, Bluetooth or WiFi). Note, however, that charge equalizers typically have modest current ratings in the range of 1 A to 10 A, so they can’t correct a grossly out-of-balance pack, nor one with a battery that has significantly less Ah than the rest.
The higher price of the rackmount 48 V batteries will be offset somewhat by not needing an external balancer, of course, as well as being easier to wire up. They will also likely be able to communicate with other batteries (wired in parallel) and/or devices (e.g. to notify the inverter to shut down at the minimum DoD, rather than a minimum voltage) and include some form of monitoring and/or coulomb counting, along with a local display of such information. That said, an external battery monitor will still be more versatile and convenient, especially if the batteries are located in a different building.
The more adventurous (and technically capable) can drop the $/kWh metric even lower by repurposing old EV traction batteries for off-grid storage use, but this is not for the faint of heart (or short of time). Unless the EV was a golf cart, you’ll have to reconfigure the cells to deliver 48 V nominal, so don’t count on using the original BMS (which probably won’t work, anyway, without a lot of code-hacking) and you’ll still be taking the risk that the battery was abused so much that it has no real usable capacity left.
The last option is venerable old lead-acid, though perhaps it’s best to relegate it to the proverbial dustbin of history. Sure, the prohibitive weight of lead-acid batteries is less of an issue in off-grid systems than it is in EVs (until you need to build the racking to hold 10 kWh or more of capacity with them, anyway) and they are notorious for not liking to be discharged below 50% of their rated capacity, though even then you shouldn’t count on more than a few hundred cycles of life. Furthermore, continuous current draw needs to be limited to a fraction of a C (typically C/4) to avoid loss of capacity from the infamous Peukert effect. This basically means that a lead-acid storage battery will have to be 2x to 5x larger in energy capacity relative to LFP, which effectively eliminates all the cost differential between these two chemistries.
Eliminate the cheaper “modified sine wave” type of inverter from consideration, as its output is really just a 50/60 Hz square wave of less than 50% duty cycle that a lot of devices won’t like.
The next key component in an off-grid system is an inverter, which converts the nominal 48 VDC from the storage battery into the 120/240 VAC required by the house, EV charger, etc. Eliminate the cheaper “modified sine wave” type from consideration, as its output is really just a 50/60 Hz square wave of less than 50% duty cycle that a lot of devices won’t like (standard dimmers and induction motors being two notable examples). The other type creates a pure sine wave by sinusoidally modulating the duty cycle of a much higher-frequency square wave, then filtering out the high-frequency components with an LC network. If this sine wave is available directly, it’s called a “high-frequency” type, and if it feeds an internal 50/60 Hz transformer it’s called—somewhat misleadingly—a “low-frequency” type.
The LF type is supposed to be better at starting heavy loads like AC compressors by virtue of the energy stored in its transformer’s inductance, but better HF inverters will cope with such loads by going into current limiting mode, rather than outright faulting off (this should be explained in the user manual [you did Read The Fine Manual, didn’t you?]), so this might be a distinction without a difference. Furthermore, the LF type draws more no-load power (1-2% of rated power is typical) to maintain the magnetizing flux in that LF transformer, and this can add up to a lot of energy over the course of a 24-hour period.
The last major choice to consider is whether to go with a standalone inverter with separate DC- and AC-input chargers, or a unit that combines one or both charging functions (the latter is often called a “hybrid solar inverter” or AIO, for All In One). Note, however, that you do not want a “grid-tie” inverter in an off-grid system, as such will not function without the presence of AC from the mains. The AIO type can be a little less expensive, because it combines all three devices into one box, but its main advantage is the ability to prioritize whether energy for the AC loads comes from the solar panels (or, very rarely, a wind turbine), the AC mains or generator, or the battery. This is an excellent solution for partial off-grid operation—e.g. running off solar during the day and the grid at night—but if you’re going purely off-grid, there is more flexibility in using separate devices, as the intelligent prioritizing won’t be nearly as useful.
And speaking of solar and wind (and hydro, for those lucky enough to have it), we’ll cover that—and the appropriate DC-input chargers for each—next time in Part Two.
This article first appeared in Issue 67: January-March 2024 – Subscribe now.
