Is the Future of Agriculture Battery-Powered?
A concept that seemed inconceivable a few years ago became reality when Milwaukee Tool introduced a chain saw that outperformed a motorized saw.
Take my word on that. I ran the Milwaukee against a popular brand of motorized chain saw, both employing 16-inch blades and cutting through ash. The Milwaukee never stalled, or came close to it, as the motorized saw whizzed. If that isn’t impressive enough, Milwaukee also just introduced an impact wrench and angle grinder that retire all but industrial-size versions of corded or pneumatic tools to dusty storage shelves. Several manufacturers are working on beefing up the capacities of their current battery-powered welders to meld ½-inch-thick steel and operate for up to an hour between recharges.
Advances in cordless tools are the tip of a Titanic iceberg in battery advances. Technology promises to make electric tractors and trucks a reality in the near future. By 2020, you will be able to recharge your pickup in the time it takes to drink a coffee, and then you’ll drive 300 miles before you need to top off.
Today’s lithium-ion (Li-ion) batteries hold more than twice the energy by weight and are 10 times cheaper than the first lithium-ion batteries introduced in 1991. Corporations are making marquee investments in battery manufacturing, such as Tesla’s $3.3 billion battery Gigafactory in Nevada.
This has set the stage for an explosive growth in rechargeable capacity, promising to quadruple battery capacity in the next 10 years. You can thank chemistry for a future when cords and combustion will be retired. All batteries create current by releasing electrons through a chemical reaction that either stores or releases a current. They take their names from the elements used in that reaction such as the nickel-cadmium or NiCd battery that now litters shop shelves after being pushed aside by the more efficient Li-ion units.
Lithium became the chemical of preference in today’s battery world because it recharges faster, holds a charge longer, and has a longer life. An innovation that promises the next big advance for Li-ion batteries is the gold nanowires serving as an electrode. These wires are 1,000 times thinner than a human hair and withstand hundreds of thousands of charges without degrading.
Beyond Li-ion to Li-air
The future of batteries can be seen in an invention at the University of Illinois and Argonne National Laboratory in Chicago. A team of researchers there has created a battery that uses the oxygen in air to react with lithium in the battery
anode electrode. Other researchers “have tried to build lithium-air cells, but they failed because of poor cycle life,” says Larry Curtiss of that research team.
The UIC-Argonne research team overcame these challenges by using a unique combination of anode, cathode, and electrolyte that prevents oxidation and buildup of battery-killing by-products. Such advances predict the development of batteries that would last the lifetime not only of the device (be it a tool or pickup truck) but also of power cells that are a fraction of the size of today’s Li-ion batteries, which recharge much faster and turn out up to 15 times more power.
Toyota scientists are testing another Li-ion approach involving solid state batteries employing sulfide superionic conductors that can recharge in just seven minutes. This approach would work in temperatures as low as -22°F. and up to 212°F.
Explorations into using different chemicals to store power predict the replacement of lithium with such elements as sodium, silicone, aluminum, and magnesium. For example, a Spanish company called Graphenano is exploring graphene batteries that could offer vehicles a driving range of up to 500 miles on a single charge and a recharge time of just a few minutes. This graphene (made of graphite) battery also discharges 33 times faster than current Li-ion batteries, which would better meet the high power needs of power-hungry tractors, combines, and trucks.
Like any other battery, a rechargeable lithium-ion (Li-ion) battery is made of one or more power-generating compartments called cells or cell assemblies. Li-ion technology uses a special molecule structure that allows current to flow three-dimensionally instead of through two-dimensional layers in a cell. The results are large increases in power and runtime and the ability to run power-hungry tools. Milwaukee Tool also employed a new generation of larger individual batteries referred to as 20700 cells to increase energy storage capacity up to an industry-leading 12 amp hours. Milwaukee has already stated its intentions to move up to an even larger unit, labeled the 21700, that packs up to 47% more energy capacity.
Cell assemblies are gathered together in a series and receive power (when recharging) or discharge power through an innovative solid metal harness that reduces flow resistance, thus delivering more power (as much as 50% more electrical flow than previous battery designs) to the tool as well as minimizing heat generation (as much as 70%). This harness is also far less likely to break if the battery is dropped (compared with wire harnesses).
The brains of lithium-ion-powered tools are electronic controls that reside both on the battery and the motor. The two microprocessors speak to each other to regulate the flow of power from the battery to the tool. The electronic control on the brushless motor calls for an increased flow of power when the tool is under load and generating more torque. The controller on the battery regulates not only how much power it releases to the motor but also how fast the battery recharges.
Key to generating the phenomenal growth in the work generated by cordless tools is the use of brushless motors that eliminate carbon brushes and the commutator used in brushed motors. In these motors, the locations of the magnets and copper windings are reversed. In a brushless motor, the magnets are on the motor shaft, and copper windings of the armature are fixed and surround that shaft. The power boost of brushless motors is possible because the copper windings are positioned on the outside of the motor configuration, which provides room to make them larger. Also, brushless motors don’t have the friction and voltage drop that brushes create by dragging against the spinning commutator.
Sizing Up True Battery Power Potential
Rating the power potential of a battery has been muddied in recent years, as voltage ratings have skyrocketed beyond such common ratings of 18 or 20 volts. But are the higher voltage batteries necessarily more powerful?
To answer that question, you also need to look at a battery’s amp hours. “Amp hours are kind of like rating a battery’s fuel tank,” explains Bob Hunter, tool evaluator for Wood magazine, Successful Farming magazine’s sister publication.
Higher voltage doesn’t always mean greater power. Voltage varies slightly within a battery’s individual cells based on the amount of charge they hold. They can produce a higher voltage at a full charge state than low.
Likewise, higher amp hours don’t guarantee you get the best run time.
When it comes down to rating the power potential of a battery, calculate its watt-hours.
The equation to do so is simple. Multiply nominal volts by amp hours. The result is watt-hours.
An example of this would be an 18-volt battery that provides 12 amp hours of energy. The watt-hours of this battery would be 216 (18×12).
Another highly reliable guide to battery power is the work turned out by the tool it supplies as measured in torque or maximum torque. True torque capacity is a reflection of both battery capacity as well as the quality of the tool’s motor and the electronic controls that regulate that motor and its battery’s functions.
Electric Trucks in Development
Last January, the Workhorse Group revealed a hybrid electric pickup truck that accelerates to 60 mph in 5.5 seconds due to its 480-hp. hybrid engine. The four-wheel-drive Workhorse W-15 lives up to its company’s name, since it’s capable of hauling a 2,200-pound payload and generating a towing capacity of 5,000 pounds. The W-15 is “designed to do anything a Ford F-150 can do,” claims company CEO Steve Burns.
Workhorse is building 5,300 of the trucks this year for fleet sales. Consumer orders will start early in 2019 for a truck that starts at $52,000 (supported by a $7,500 tax credit).
Electric car pioneer Elon Musk reports his firm is on the verge of introducing a Tesla pickup that will have dual-motor all-wheel drive “with crazy torque and a suspension that dynamically adjusts for the load,” boasts electric car pioneer Musk.
An all-electric semitruck isn’t far from the market, either. Thor Trucks has developed an electric semi that can haul 80,000 pounds of cargo and travel up to 300 miles on a single charge (shown above). Power train options for the truck range from 300 to 700 hp. with full torque starting at 0 rpm. The company claims the Thor runs 70% cheaper than diesel semis. A limited fleet of demonstration trucks are now available from the company.
Radical Battery Redesigns
Researchers are exploring different chemical compositions to boost the electrical carrying capacity of today’s lithium-ion batteries.
A lithium-ion (Li-ion) battery comprises anode and cathode electrodes and an electrolyte held in an insulator separation wall composed of microscopic holes. In a charged state, lithium atoms are stored in the anode electrode. When the battery becomes part of a closed (or completed) circuit, it begins discharging. This causes an oxidation reaction to occur between the lithium atoms (in the anode electrode) and the electrolyte solution, resulting in electrons jumping ship from the lithium atoms to create lithium ions. The electrolyte solution only lets ions pass through it to the cathode electrode where a reduction reaction creates energy. Charging the battery reverses this process.
A battery created from lithium and sulphur (Li-S) has the potential of carrying five times more energy by weight than the Li-ion battery. In a Li–S battery, the metal oxide electrode is replaced by sulphur, which has the ability to hold more lithium atoms since each sulphur atom bonds to two lithium atoms. The graphite electrode is replaced by a sliver of pure lithium metal that does double duty both as an electrode and the supplier of lithium ions.
This approach draws air into the battery where oxygen acts like an electrolyte. Such breathing batteries offer a huge weight advantage over other battery approaches since they don’t need to carry around one of their main ingredients. A lithium-oxygen (Li–O) battery can, in theory, store energy as densely as a gas engine, which is 10 times more than the batteries used in today’s cars. The challenge with Li-O batteries is that they lose carrying capacity rapidly with each recharging cycle. Researchers are exploring cheaper breathing batteries based on sodium-oxygen
(Na-O). The Na-O battery provides only half the energy density of Li-O but is still five times more powerful than Li-ion batteries.
Redesigning the electrodes in batteries and replacing the lithium with heavier ions, such as those offered by magnesium, has potential since magnesium ions carry two electrical charges each vs. the one charge carried by lithium ions. But recharging and release-response time is slower with Mg-ion batteries because magnesium ions move much slower than lithium ions.
Electric Tractor Now a Reality
The dream of battery-powered tractors became reality this summer when a limited number of Fendt model e100 Varios went to work on farms and municipalities in Europe. Capable of operating for up to five hours on a charge, the 67-hp. Vario draws off of a 650-volt lithium-ion battery. Plus, the battery can be recharged up to 80% in just 40 minutes.
Fendt reports that the e100 was designed to power both conventional (via a PTO or hydraulics) as well as electrified implements. It is expected that the e100 Varios will likely not be generally available until 2019.
AGCO (Fendt’s parent company) is not the only firm taking a serious look at electric tractors. John Deere revealed an all-electric prototype in 2017 at a machinery show in Paris that turned out a whopping 174 hp.
Called SESAM (Sustainable Energy Supply for Agricultural Machinery), the Deere prototype is based on the company’s 6R series chassis equipped with two electric motors. The SESAM’s battery pack offers enough energy to power the tractor for up to four hours. Deere estimates the tractor is at least three to four years away from commercial production.
German off-highway engine manufacturer Deutz is also in the hunt for electric horsepower. That firm recently spent $117 million to implement the E-Deutz strategy. The first products from that investment are expected in about two years.