Even batteries are becoming hi-tech
They are probably the component that has changed the least over the years, but changing requirements in terms of powering services and equipment are increasing amperage and starting current. In some cases, this has led to the installation of two or even three batteries, synchronized by an electronic equalizer
Compared to other sectors, the evolution of the battery-alternator combination is really quite minor. Consider how much the control panel, electronics, seat, and even the simple air conditioner, now an electronic climate control system with precise temperature regulation, have changed over the last thirty years. The battery, on the other hand, appears to be the same as ever: a box that stores electrical energy and returns it when it is time to start the tractor. Yet even the battery has changed, is changing, and will continue to change in the near future. This is mainly to adapt to the changing needs of modern agricultural machinery. We summarize these changes below to provide a clear picture of the situation.
Electricity consumption is skyrocketing. A quarter of a century ago, once started, a tractor had to power the lights (in case of night work), a few on-board instruments, and just the air conditioner. Today, it is difficult to keep track of all the electrical applications present. The air conditioner, of course, has evolved into a complex system, summarized by the acronym HVAC (heating, ventilation, and air conditioning), which includes ventilation and heating. Then there is the complex instrumentation: two or even three 6- to 12-inch monitors, plus all the electronics behind them (control units, various sensors, operating system computers), satellite antenna and automatic guidance system, Isobus connection, and so on. Under the hood, still on the subject of electrical devices, we find the radiator fan (in certain models), which alone absorbs several watts, as well as the fuel pump, the wastegate, and the EGR valves. In addition, there are dozens of solenoid valves for the hydraulic, power steering, and braking systems. On some models, even the continuously variable or powershift transmission actuators are electrically operated. Finally, there are outputs for connecting additional monitors and for the ever-increasing requirements of the implement. Take, for example, modern seed drills, all equipped with electric metering devices and, in some cases, even ventilation systems with electric motors. The only item that has seen a reduction in power consumption is lighting: the adoption of LEDs instead of halogen headlights has led to a significant drop in power consumption (approximately 60-80 watts compared to 180-200 for halogens).
As a rough estimate, it can be estimated that over the last 25-30 years, agricultural vehicles have seen an increase in electricity requirements of around 40%: if a machine from the 2000s was satisfied with 150 Ah/day, currently 200 to 220 Ah are needed to operate a vehicle of equal power (say around 200 horsepower). Not only that, but the sophisticated technology installed on tractors today is very sensitive to power surges and power losses. If the battery does not work perfectly, even before causing starting difficulties, it will cause malfunctions in some control units or even in unexpected places, such as the injection system or the armrest controls. It is therefore essential that batteries not only guarantee starting, but also current stability during operation.
Starting, precisely. With the same power, engine volumes (and with them the force needed to turn them) have been reduced. However, tractors have increased in size: while in the 1990s they did not exceed 300 Hp, today they easily exceed 400 Hp, so modern starting systems are used to start 6-cylinder engines with a displacement of 9 liters. Moving into the maxi-tractor segment, we find that the Case IH Quadtrac is equipped with a 12.9-liter engine, while the Mercedes-Benz Xerion 12 has a 15,600 cc engine. Even larger volumes are found in harvesting machines: modern combine harvesters all have a volume of around 12 liters, while the largest forage harvesters double this (with the 24.2-liter Liebherr D9512, for example, or the 20,000 cc Fpt Cursor V20). These engines are derived from other sectors (such as heavy transport) that often require a 24-volt starting system, so manufacturers have had to work hard to meet this need without revolutionizing the electrical system as a whole.
Starting power, amperage: what has changed. Batteries must keep pace with these developments. They are required to provide both higher amperage and higher starting power. A brief explanation: the continuous demand for electricity, for example, from the air conditioning or displays, requires a higher battery amperage, although the necessary energy is supplied by the alternator when the engine is running. When starting, the ignition of the electronics, the fuel pump, and various devices all rely on the battery, which requires amperage.
To start the engine, on the other hand, the battery must have a high starting power, also known as CCA (Cold Cranking Amps). Intuitively, starting a 6,000 cc engine or a 15,600 cc engine places different demands on the battery. Starting power and amperage are not mutually exclusive: batteries can have high values for both, but in that case, the costs and weight increase significantly, as specific plates must be used for high starting power and thick enough to guarantee a considerable number of amperes.
Therefore, there are two solutions: a battery that combines starting power and amperage, albeit at a higher cost, or the Dual Battery option, i.e., two (or more) batteries installed on the vehicle. The first, with high starting power, activates the starter (even when cold, a typical condition for agricultural vehicles), and the second powers the electronics and various services. The technology inside the batteries can be traditional (the classic lead with liquid acid) or more recent. This is the case with AGM (Absorbent Glass Mat) batteries, where the mixture of water and acid is not free but is contained in fiberglass sponges.
Technological evolution. Accumulators, also known as batteries, have not changed much in recent decades. In fact, on closer inspection, the principle behind them is the one discovered by Volta in 1799, with the first battery. However, there have been some changes in recent years. For example, sealed batteries have been introduced, which do not require maintenance. They can also be placed on their side because they are hermetically sealed. Above all, they do not need to be topped up with liquid, as they do not leak through evaporation.
Other significant innovations concern AGM and Gel batteries. We have already written about the former: they are manufactured using a system of acid stabilization in solid membranes, reducing the need for maintenance, self-discharge, and potential inconveniences from vibrations or jolts, which are common in agricultural activities. Gel batteries are not currently widespread in rural areas; however, they adopt a similar principle to AGM batteries, except that the acid is clumped together in a gel. Again, no refilling is required, and self-discharge is greatly reduced. Compared to AGM batteries, gel batteries are more resistant to prolonged use and, in many cases, can be considered deep-cycle batteries. This term refers to batteries that can be discharged almost completely (even to 20% of residual energy) without showing any accumulation problems or losing their ability to recharge to 100%, a problem typical of batteries used for starting. In a sense, it could even be said that deep-cycle batteries are the opposite of starter batteries: the latter are designed to deliver high loads for a very short time, while deep-cycle batteries deliver continuous current for long periods, discharging well beyond 50%.
The problem of so-called charge memory and deep discharge has been solved for cell phones, computers, and even transportation by the adoption of lithium-ion batteries. This technology is slowly and partially replacing lead for starter batteries as well. "Lithium is not just the future, it is already the present in numerous applications, even if it will take a few more years to really spread in the agricultural sector," explains Alessandro De Rossi, from the marketing department of Yuasa Italia, the world's leading battery manufacturer. "It is a technology that offers several advantages: the main one," he adds, "is greater ease of charge acceptance, which reduces the working time of the alternator and consequently saves fuel. In addition, for the same amount of stored energy, lithium batteries are lighter and less bulky than lead-acid batteries."
Two, three, four batteries. Let's complete the picture by summarizing how agricultural machinery manufacturers are coping with increased electrical power requirements. The most common solution is to increase battery capacity because the starting current required for ignition is not significantly different from its previous level. This is due to the decrease in engine size over the years, while the kW output has remained the same. On the other hand, compression ratios are higher on average, making starting more complex and still requiring higher CCA. These changing requirements apply even more so to the energy consumption of the many newly adopted devices, as we have seen above. For this reason, a modern tractor is equipped with batteries with an amperage of 120 to 200 Ah (and above), depending on the power, and alternators that consequently have a range between 100 and 170/200 Ah. Sometimes, in fact, the alternator is doubled to ensure sufficient energy to cover a requirement that, for a 200 Hp machine, easily reaches 240-250 A per day (approximately 30 amperes/hour).
The use of a single battery is currently the norm, but dual-battery solutions are on the rise. Some manufacturers, such as Massey Ferguson, had doubled the circuit in the past, but have returned to a single battery for models launched in the last decade. However, dual batteries are becoming common on larger models. This is the case with Case IH Magnums, New Holland T8s, and some Valtra ranges, which have one battery for starting and another for powering various services.
Finally, the so-called dual battery is much more common on large harvesting machines, where engines regularly exceed ten (and even twenty) liters in volume and, as we have already mentioned, require 24-volt systems for starting. These are voltages that a single battery could not provide, so at least two are needed. These work in parallel, therefore, with 12 volts of voltage, during normal machine operation. During start-up, however, a relay connects the batteries in series, supplying 24 volts of current to the starter.
But that's not all. Some machines have three batteries. This is the case with John Deere's F9 mulchers, which have three 175A batteries, and Case Ih's Quadtrac articulated maxi tractors powered by Cursor 16 engines. These vehicles use two 12-volt batteries, which can work in parallel or in series. A third battery acts as a buffer to maintain 12V power to electronic applications, while an equalizer coordinates the charge between the three devices to avoid imbalances. We conclude with what we believe to be the record-breaking machine: New Holland's FR 920 forage harvester, which has four batteries.
