By Glenn Hansen
We keep comparing battery-powered equipment to gas-powered equipment; that’s understandable with internal-combustion engines being the norm in outdoor equipment for so long. But today, cordless mowers and blowers and trimmers account for more than 60% of OPE unit sales to homeowners.
Yes, the commercial side of cordless is behind the homeowner side in sales penetration as pro users have been slower to embrace battery-powered equipment. But as more manufacturers increase their product offerings and their retail real estate, commercial users will increasingly turn to batteries.
This is not a “pick one” proposition. Major manufacturers such as Stihl, Echo and Husqvarna repeatedly say they are dual-fuel suppliers of equipment. Gas-powered equipment is not going away. Maybe we’ll see quieter and cleaner internal-combustion engines. Or maybe alternative fuels can be more available and affordable. (And while I might personally choose battery-powered OPE, I still fill my 1965 GMC V6 with expensive ethanol-free fuel.)
Prepping the crystal ball
For this feature, I asked several manufacturers about the near-term evolution of their battery-powered products. I asked about battery chemistry and cell types and supply chain and electric motors and more.
That’s the point. We all need to ask more questions about batteries and electric motors and battery management systems. We have asked questions over the years about fuel delivery systems and gas tanks and engine cooling – now it’s time to ask about batteries.
I knew that not every manufacturer would answer my questions. Some answered selectively; some declined to answer at all. I do always allow companies to simply respond with written answers via email. Non-answers don’t mean anything about a company’s batteries or battery products. No need for me to call out certain OEMs here, but you might see them by not seeing them. Finally, I also spoke with a battery expert outside of OPE for some non-branded perspective.
Battery Evolution
We generally compare batteries and gas using performance metrics like run time or retail metrics like initial cost. Perhaps we should also compare annual maintenance, fumes, noise, vibration and their impact on users. This could get opiniony and we’re not doing any of that now. Let’s look at batteries by themselves and how certain manufacturers got to where they are.
To get started, see the sidebar “Battery Chemistry” on p. 20.
Mean Green: The case for NMC batteries
“We learned the hard way,” said Matt Conrad, director of engineering for Mean Green mowers. “We went from lead acid golf cart or truck batteries, and we jumped into LFP in about 2013. It made sense at that time because we’re flexible and we’re small. We were able to get on the NMC train in 2017 and there were a lot of good benefits there. LFP has been taking a good amount of press in the last few years and that has to do with costs. But the downside is the density.”
Conrad said that one of the main goals at Mean Green mowers was to hit 5 acres of runtime. The early lead-acid batteries, he said, weighed about 800 pounds. They tried all sorts of deck, chassis and blade designs to bring the total weight down and make those batteries work.
When Tesla EVs gained popularity using LFP batteries, Mean Green tried that chemistry with swappable batteries. “We started selling more of those than we did lead-acid battery mowers, but the swappable battery frustrated a lot of people,” he said. The users, said Conrad, didn’t want to change from gas-powered mowers that they were used to refueling; they didn’t want to stop and swap batteries mid-mow.
“We were trying to get enough lithium in there to run it all day on one charge, even beyond 5 acres. And that’s what morphed into the NMC batteries. It was like ‘wow, this is going great.’ It’s lighter, more energy dense and we saved some money.”
It wasn’t all about the NMC chemistry. “It was a lot about supply chain. Over the years we’ve really balanced the pros and cons of chemistry and the supply chain because we just can’t compete against the car industry. It’s very challenging,” said Conrad.
Mean Green is aware of the heat concerns with NMC cells and incorporates safety mechanisms in layers to protect users and the equipment.
Greenworks: The case for LFP
“Ford is setting up an LFP manufacturing facility here in U.S. They are moving away from NMC to LFP. The fundamental reason they say is safety,” said Yin Chen, CEO of Greenworks. “We are the only brand in the whole industry using LFP battery for electric equipment. One downside is a low-temperature situation. The second downside is the weight; LFP is going to be 10% to 15% heavier than NMC.”
To counteract the low-temp. operation downside, Greenworks uses heating pads to keep the battery warm based on temperature sensor readings. For the weight disadvantage, Chen said it’s really only a problem on spec sheets. “Our battery (Chen points to a large zero-turn) right now is 390 pounds. If we used NMC material, we’re going to be 30 pounds lighter. But it’s 30 pounds lighter for a 1,200-pound machine. That’s nothing. But with LFP we triple the life from 500 to 2,000 cycles.”
Ford is indeed building an EV battery plant known as BlueOval Battery Park in Michigan. The plant will manufacturer LFP batteries using a Ford-specific design, though the car maker is getting assistance from CATL, the largest battery manufacturer in the world, based in China. Ford said it will make LFP batteries without using Chinese-sourced materials.
Back to Greenworks and its use of LFP. Chen reiterated the safety message about LFP and added the increased lifecycles. “The LFP is 2,000 cycles,” he said. “If you’re using 200 cycles a year, which is one charge and discharge per day, that’s 2,000 days. That’s basically 10 years of battery life.”
What about other manufacturers?
“Whether you look at sodium, whether you look at LFP, whatever the chemistry is, everybody’s looking to do the same thing,” said Todd Zimmerman, SVP of dealer sales, operations and product for Kress tools. “We all want more power, we want faster charging, and we want longer battery life.”
“It’s just what chemistry is going to be better than the next chemistry. We’ve read white papers for years on different chemistries trying to do it in development of battery powered equipment.”
Zimmerman said that Don Gao, the CEO of Positec Corporation, Kress parent, worked with the University of Waterloo (a well-known engineering and research campus in Ontario, Canada) to invest in and create proprietary battery chemistries for its equipment. “We were able to come up with those chemistries working with lithium ion and other chemistries” that allow battery cells to perform to Kress specifications. He said it’s about reducing resistance in the battery cell.
Stihl uses a lithium iron phosphate (LFP) battery in its zero-turn mowers. “It’s a little heavier but provides other attributes that we find to be better for that particular use case,” said Paul Beblowski, Stihl product manager. “Each particular chemistry is linked to the performance of the battery along with other attributes like its weight. You end up having trade-offs between performance, weight, cost, temperature profile, those sorts of things.”
Milwaukee Tool states it uses lithium-ion batteries in its equipment, not giving further specifics regarding chemistry. You could guess that most manufacturers use NMC batteries in their handheld equipment for its lighter weight compared to LFP batteries. Even Chen of Greenworks said his company uses NMC in its handheld equipment for that reason.
Future of Cell Chemistry?
Solid-State Batteries: In these batteries, liquid or gel electrolytes are replaced with solids. This technology could deliver higher energy density, faster charging capabilities, increased safety, and greater flexibility in form factor. Solid-state chemistry has been discussed for years. Samsung SDI is reportedly ready to mass produce solid-state batteries beginning in 2027.
“It is known for better safety and is more energy dense than NMC,” said Conrad. “I’d prefer to go there next but I don’t know if we will. Going to a lithium iron phosphate battery would almost be like going backwards at this point.”
Sodium-Ion Batteries: The abundance and global distribution of sodium make a sodium-ion battery appealing. This reduces supply chain disruptions and lowers material costs. While their energy density is currently lower than lithium-ion, their cost-effectiveness and improved supply chain resilience make them an attractive alternative, especially for less energy-intensive or cost-sensitive OPE applications.
Size
Most tool battery packs are made up of cylindrical battery cells. There are two common sizes: the 18650 cell (18mm diameter, 65mm length) and the 21700 (21mm, 70mm length). A battery pack for a handheld string trimmer might contain 8 or 12 battery cylinders. A Tesla Model 3 contains about 4,000. And they could very well be the same cylinders. The Tesla CyberTruck uses primarily 4680 size battery cells.
The 18650 size is common and older. Tesla teamed with Panasonic to create the 21700 cell in 2017. The increased volume improved energy density. For power equipment makers, battery packs changed shape to accommodate the larger 21700s, but it increased efficiency too. The newer cells can also be more cost-effective to assemble due to fewer components and fewer spot welds required during manufacturing.
Shape
If you’re thinking about your phone right now and wondering about its battery, it’s a pouch cell, using thin layers of metal and chemicals encased in a rectangular tinfoil-like pouch. Some tool makers use these pouch cells too.
“Our cyber pack batteries are pouch designs,” said Zimmerman from Kress. “It allows us the best design to utilize the chemistry versus rolling that up into a cylindrical design.”
Stihl uses pouch technology in its top-of-the-line AP 500S battery. “We’re able to pack more energy content into that battery than any other,” said Beblowski. “And we’re able to extract a lot of power out of it, extremely quickly, and all of that is Stihl proprietary product.”
“Pouch cells are well suited for delivering high power in a compact form factor but are less ideal for applications requiring extended runtime, frequent charging cycles, and effective heat dissipation,” said Zafir Farooque, group product manager at Milwaukee Tool.
Another advancement in battery cylinders is the tabless design. A tabless cell increases the points of contact, basically, for the cell’s electrodes, and helps reduce resistance. Instead of using single points of contact for both the anode and cathode, a tabless cell is better able to use all the electrode material. That means increased storage, faster charging and other benefits.
Tabless is another Tesla creation, announced on Battery Day in 2020. It also brought out the 4680 cell size at the time.
“The tabless design will continue to catch on,” said Zimmerman from Kress which uses tabless cells. “The tabless design allows the cell to be smaller, more compact. It allows the cell to stay cooler longer, so you can charge it faster, have more life cycles out of it, and get a little bit more power out of it. We’ve adopted tabless into batteries to operate for power tools and for outdoor power equipment. So if you compare a tabless battery to a typical cylinder battery cell, it’s generally half the size, half the weight.”
We know that Milwaukee Tool uses some tabless cells too. “Tabless cells have unlocked substantial benefits, including enhanced power delivery, reduced heat generation, faster charging and extended battery life,” said Farooque, of Milwaukee Tool. “This innovation has empowered us to continue pushing the boundaries of performance across our systems.” He added that tabless cylindrical cells also help Milwaukee integrate its cooling system using charger-mounted fans to pass air through ventilation channels in the battery and directly cool the core.
The View From Outside OPE
As I was searching for more sources for this story, I found Travis Cournoyer. He’s a PhD battery designer with experience working for Tesla and Rivian and others. He helped me see batteries from beyond the equipment.
On battery chemistry: “If you look at all the chemistries, LFP is not terribly exciting. It doesn’t deliver a lot of power. You can’t charge it quickly and it’s not that energy dense. A lot of the nickel chemistries have lots of energy in a small package. And LFP has a specific downside that makes it unique from all the other lithium-ion batteries – that’s its voltage curve. When it’s almost charged, it’s very steep. It goes up very high, but then in most of its use from 70% or 80% state of charge down to like 20, it’s flat. That changes your entire architecture of your product. So committing to LFP is a big commitment that you’re not sharing the development of that product with any other chemistries out there. It’s low cost, but also high risk if it doesn’t work out.”
“Any nickel-loaded chemistry has lots of energy and you can dispense at a typically high power. You can charge it and discharge it very fast. Nickel-loaded chemistries have the highest energy density you can get in a reasonable performance that matches most of the need, which is why it penetrated so deeply across markets. It’s not inexpensive, but its value-to-cost ratio is the best in the lithium-ion world today.”
While Cournoyer shared a lot of knowledge around cost per megawatt and the future of smart batteries, his best advice was more down to earth when considering getting top performance and life out of a battery.
“I say batteries are like people, right? You don’t want them too full. You don’t want to deplete them too much. You want them to be happy, you know, kind of in the middle. Lithium-ion batteries respond well to temperatures that are almost identical to the human body. Not too cold, not too hot. Do that and don’t overwork it. If you try to get too much power out of it, just like if we work too hard, the battery sweats and gets stressed inside. Its electrodes start to crack, quite literally. So in a lot of ways, batteries are like people.”
“But professionals don’t want a battery they have to baby, right? So they throw them around and drop them and that hurts. Then they have to replace them every couple years.”
Travis Cournoyer, PhD, is an engineer and author with over a decade of experience designing, building, and testing advanced battery systems for electric cars, trucks, vans, and airplanes.
What’s left in this story?
Motors
The integration of brushless motors, which are inherently more energy-efficient and provide greater torque per watt, might be the more important part of the story.
“The part that has really helped create the conversion is batteries working with brushless motors. And the efficiencies that come with those designs. With a brushless motor,” said Zimmerman from Kress, “you have the opportunity to actually create software for that brushless motor to do different things at different levels.”
We’ll save motors for another time, a lot to discuss there.
Cost
The cost of lithium-ion batteries is influenced heavily by raw material markets on the supply side and EV interest on the demand side. OPE manufacturers benefit from the technological advancements and cost efficiencies achieved in the EV sector, effectively leveraging the innovation and scale of a larger industry. At the same time, the battery cell needs of power equipment market are comparatively small, leaving equipment OEMs with relatively little purchasing power.
“Up to 2020, prices for lithium batteries kept coming down,” said Conrad from Mean Green, “until Covid, then prices went right back up. Now the hot one is tariffs, and that’s the challenge now. We were seeing pricing come back down about a year ago, maybe to where it was in 2019. NMC chemistry has been pretty stable overall.”
Battery Management
Equipment batteries incorporate intelligent Battery Management Systems (BMS) that continuously monitor and optimize individual battery cells for individual tools. “Our battery management interacts with the tools because each of our batteries has a brain built into them that interacts with the tool,” said Beblowski. “It enables a conversation where it says, ‘hey, I’m this type of battery.’ The tool says, ‘I’m this type of tool,’ and they work together to create that ideal performance.”
These systems manage power delivery, regulate temperature, and facilitate communication with power equipment. It can also include safety sensors. Advanced BMS can even prevent charging when ambient temperatures are too low, which helps to avoid accelerated aging and potential damage to the battery cells. There is a future where a tool’s BMS will allow other communication as well. That can raise privacy concerns, but manufacturers are looking at that.
Cooling Solutions
The inherent design of larger cells, such as the 21700 size, allows for more efficient heat dissipation due to their increased surface area and volume. Some battery packs further enhance passive cooling by using improved internal designs and materials that reduce electrical resistance, thereby minimizing heat generation within the cells themselves.
Our next questions
Battery life cycle
Recycling
Pack manufacturing and durability
Energy cells or Power cells?
More to come!
Battery Chemistry
The landscape of lithium-ion batteries in OPE is currently defined by the two dominant chemistries that make up the battery cell’s cathode: Lithium Iron Phosphate (LFP) and Nickel Manganese Cobalt (NMC). A battery is made up of a cathode, an anode, and electrolyte for the reactive portion. The cathode is the positive end, the anode is the negative end, and the electrolyte helps the ions move across a separator to produce energy.
Lithium Iron Phosphate (LFP) Batteries:
These batteries, also known as LiFePO4, are regarded for their stability, safety and longer cycle life. That’s counted in thousands of charge-use cycles for LFP instead of many hundreds of cycles typical for NMC batteries. Iron and phosphate are more abundant, less expensive, and less geopolitically sensitive compared to cobalt. That’s the C in NMC batteries, though some manufacturers are finding ways to lower the amount of cobalt. LFP batteries exhibit a lower energy density, typically ranging from 90-120 Wh/kg, and operate at a nominal voltage of 3.2-3.3V. They demonstrate superior performance at lower states of charge.
- LFP batteries offer a long cycle life, typically exceeding 2,000 cycles, making them a durable choice for various applications.
- They have a lower energy density compared to NMC batteries, meaning they are often heavier for the same energy storage capacity.
- LFP batteries are generally available at a lower cost, that’s largely why their share of the global electric vehicle (EV) battery supply more than doubled since 2020.
- LFP batteries are commonly used in power tools, electric buses, grid energy storage, and stationary applications where safety, longevity, and a lower cost per cycle are important.
Nickel Manganese Cobalt (NMC) Batteries:
NMC batteries offer a higher energy density, with specific energy ranging from 150-220 Wh/kg, and a higher nominal voltage of 3.6-3.7V. This superior energy density translates into physically smaller battery packs for a given capacity; that’s an advantage in applications where space and weight are critical constraints like in handheld equipment. NMC batteries also have a shorter cycle life and are more susceptible to thermal runaway at elevated temperatures or if subjected to overstress or mishandling.
- These batteries do come at a cost premium. They might cost 20% more than LFP batteries, thought that cost differential has narrowed in recent years.
- NMC batteries typically have a higher energy density compared to LFP batteries, which means they can store more energy in a smaller and lighter package.
- They offer a good balance between energy density and cycle life, making them suitable for a wide range of applications, including electric vehicles and portable electronics.
- NMC batteries have faced scrutiny due to the cobalt content in some formulations. Cobalt mining has raised concerns regarding environmental degradation and labor conditions in certain regions.
- Efforts are underway to develop cobalt-free NMC variants to mitigate these environmental and ethical concerns.
- NMC batteries are widely used in electric vehicles, laptops, smartphones, and a variety of consumer electronics where compact size and high energy density are essential.