Extending Battery Life in Transportation and Mobile Applications with Supercapacitors

Battery life is becoming one of the most critical factors in system performance and reliability, and the introduction of supercapacitors will help extend battery life in two major application areas. First, they can dramatically reduce the cost of battery replacement in vehicles such as trucks, cars, boats and electric generators. Second, they can extend the operating time of mobile devices such as smartphones and tablets by 400%.

With unlimited recharge capacity and high energy density, supercapacitors can provide guaranteed engine starting capabilities for automobiles, heavy-duty transport vehicles, ships and traction locomotives over a wide temperature range and even in the event of battery failure.

In mobile electronic systems, supercapacitors can control peak currents in a variety of different application scenarios. With better control of discharge, batteries can maintain their peak power longer and extend the operating time of the device.

Studying the market needs of these two major application areas shows the benefits of adding supercapacitors, but in completely different ways.

Engine Starting

The most critical factor in the transportation field is engine starting reliability. Every time a lead-acid battery starts the engine, it is one step closer to the end of its life. Using supercapacitors in the ignition system can relieve the battery from the harsh engine starting discharge that usually reduces its life. The typical lead-acid battery can extend its useful life by 70% in specific applications by using supercapacitors. In addition, starting the engine with supercapacitors can achieve higher reliability at colder temperatures.

In the trucking industry, the use of supercapacitors helps improve daily operations in several ways. Typically, 18-wheel trailers and buses are equipped with three to four batteries. When one of the batteries fails, the vehicle requires a relatively expensive jump start, which can cost up to $600 per start.

In addition, the battery replacement costs about $200 each, which is why market researchers have found that battery theft in trucks and buses is a big problem. In addition, the starting reliability of lead-acid batteries drops sharply when the temperature drops below minus 10 degrees Fahrenheit. Supercapacitors can extend this range to minus 40 degrees Fahrenheit, further improving engine starting reliability in areas where cold weather conditions are prevalent.

Market research conducted by Cooper Bussmann shows that 60% to 80% of engine failures in electric generators, which are usually used in construction sites without access to the power grid, are caused by battery problems. The report also points out that battery theft is a serious problem here as well.

Locomotives must be able to operate reliably in all conditions in order to meet very strict train scheduling requirements. Cold weather is one of the most common operating conditions for locomotives. Supercapacitors can help start engines at minus 40 degrees Fahrenheit, while lead-acid batteries cannot work reliably at minus 10 degrees Fahrenheit.

Marine engine starting is critical because they operate in conditions where they cannot be started by hookup, and environmental conditions such as storms or high tides require high reliability. In addition, other electrical systems on ships for electronic equipment (fish finders and navigation) will put a considerable load on lead-acid batteries when the engine is not running.

In passenger car applications, emission standards will drive automakers to install start-stop systems. It is predicted that by 2017, 40% to 70% of new cars will be equipped with start-stop systems. Requiring automobile engines to automatically shut down after idle periods requires more restarts, which will put more stress on lead-acid batteries and shorten their life. Today, most automakers install a second battery to ensure the reliability of the start-stop system.

Supercapacitor Installation Methods

Supercapacitors can provide many benefits in all of the above situations. They can be installed in one of the following three ways:

● Direct parallel

● Supercapacitor starter

● Smart start

The direct parallel method is to install the supercapacitor bank between the battery and the engine electrical system. It provides the simplest and cheapest way to make supercapacitors work with existing batteries. The schematic diagram of this method is as follows:

Using the direct parallel method above, the supercapacitor can extend the battery life and share the high current load of the system. But it is still affected by the internal load leakage, so if the headlights are still on after the engine is turned off, the car may still not start.

The battery life under typical operating conditions is approximately 3 to 4 years. Adding a supercapacitor to the system can significantly extend this battery life, making replacement less common and greatly improving the reliability of engine starting. The

supercapacitor starter method is designed to ensure engine starting, which is not easily affected by internal load leakage. The supercapacitor is directly connected to the starter, and the lead-acid battery only powers other electrical systems in the car, such as the radio, lighting and air conditioning. The schematic in Figure 2 shows a typical configuration of a supercapacitor starter.

The following two photos show the design of supercapacitors for heavy-duty vehicles. There are three terminals on the supercapacitor, one of which is connected to the starter only, and the other positive terminal is connected to the battery for charging. This wiring method can ensure the longest battery life because the lead-acid battery is no longer subject to the typical 1000 amp discharge current required for engine starting.

The smart start method provides the flexibility to start the engine with either the battery or the supercapacitor or both. Because the starter receives its charge from the supercapacitor, it can operate at lower temperatures. Starting with the supercapacitor can be as low as -40 degrees Fahrenheit. The smart start design is optimized for starting and system function. The controller determines how much energy to draw from the supercapacitor, which provides the longest battery life among the three installation options. Starting is also not affected by internal load.

Supercapacitor vs. Battery Comparison

Figure 4 lists a comparison table of supercapacitor specifications and battery specifications. The batteries in this table cover a variety of technologies, from the lowest performance lead-acid batteries to higher performance lithium-ion batteries.

Supercapacitors can significantly extend battery life in a variety of vehicles, and they are able to operate over a wider temperature range. Vehicle electronic systems can be optimized for reliability, cost and flexibility to meet the most pressing needs of the application field, whether it is an 18-wheel trailer or a ship, bus or electric generator.

Designers of these systems should choose supercapacitors to provide long life and high reliability. A key parameter to consider in supercapacitor design is ESR performance. For transportation needs, lower ESR and long-term performance means higher reliability and lower costs in the long run. In addition, weight, cost and temperature performance should be carefully considered.

Cooper-Bussmann offers a wide range of supercapacitor solutions for engine starting applications, from XB series and XV series cells to XVM modules. They are designed to cover a variety of applications in the transportation field and can be selected based on electrical system requirements and battery type.