As modes of transport, trains and electric vehicles (EVs) have a lot in common. Both provide the joy of travel, are safe and convenient and, by expanding the possibilities of electric mobility, both contribute to the realization of a sustainable society.
At Nissan, we are now developing an entirely new way to combine the technologies used in both rail travel and EVs. For batteries in railroad crossing devices, East Japan Railway Company (JR East), one of Japan's leading rail providers, is trialing repurposed Nissan LEAF EV batteries.
Railroad crossings are essential for train operation and road traffic safety. Rail companies install emergency power supply units at each crossing to ensure they operate properly at all times. This includes during scheduled maintenance work and temporary power outages. Currently, these emergency power supply units use lead-acid batteries. However, efforts to replace these with repurposed Nissan LEAF batteries began in January 2021 at the Atago railroad crossing on the Jōban Line, which runs through Minamisoma City in Fukushima Prefecture.
Repurposing EV batteries
A Nissan LEAF's lithium-ion battery retains 60 to 80% of its electricity storage capacity at the end of its life cycle in a car. Therefore, by reusing used EV batteries, we can direct this remaining energy capacity elsewhere, such as into new replacement vehicle batteries or stationary batteries. Nissan's partner, 4R Energy Corporation, is responsible for this effort. Repurposing vehicle batteries can reduce the CO2 emissions and rare resource usage associated with building a new battery from scratch. On top of that, it adds additional value to EV batteries, increasing the value of EVs in general, and leading to their wider adoption.
Benefits not limited to sustainability
For Kaito Tochihara, assistant chief researcher at the East Japan Railway R&D center, when it comes to emergency power supply, switching from lead-acid to repurposed EV lithium-ion batteries not only promotes sustainability, but also leads to improved performance from the battery itself.
Compared to lead-acid batteries, the reused lithium-ion variety requires only 1/3 of the charging time. They are also far more durable, lasting on average 10 years, compared to 3-7 years for a standard battery. Tochihara is particularly interested in battery maintenance.
"With lead-acid batteries," he said, "we have to periodically visit railroad crossings to check the state of charge and any deterioration. However, with repurposed lithium-ion batteries, there is a control system attached, similar to an EV, so we can remotely check the battery's status. This should lead to improved maintenance standards. This system also enables preventative maintenance by informing us of the battery's status before its voltage becomes too low."
Safety and security at railroad crossings
Tochihara explained that "railroad crossings are points of contact between trains and public roads, so they have to be extremely safe and reliable. At 4R Energy Corporation, we develop our repurposed lithium-ion batteries from batteries designed for cars. Similar to a railroad crossing, such batteries require a high level of safety and security. Their reliability gives us the confidence to carry on our efforts."
Takuya Kinoshita, of the Technical Solutions Department at 4R Energy Corporation, explains that the company's repurposed lithium-ion batteries feature four degrees of safety.
1. Nissan LEAF's track record: The Nissan LEAF, source of the reused batteries, has had no serious incidents due to battery quality over the 10 + years since its launch.
2. UL1974 International Standard: For its battery recycling/remanufacturing process, 4R Energy Corporation has acquired UL1974 International Standard certification related specifically to the recycling of storage batteries.
3. Nissan LEAF control concept: 4R Energy Corporation repurposes batteries according to the same control concept used in production of the Nissan LEAF.
4. Designed for safety: Similar to the Nissan LEAF, the repurposed batteries are designed to prevent explosion in the unlikely event of an accident.
In addition, the Nissan LEAF, which is sold around the world, is designed to cope with various climates and conditions. The same can be said for the LEAF's lithium-ion EV battery. This, Kinoshita says "is a strength suited for railroad crossings in harsh environments." However, before reused batteries can be employed wholesale in railroad crossing devices, some remaining issues must be resolved.
Withstanding lightning surges
If lightning strikes an EV, the electricity flows to the ground through the vehicle's body. This prevents the sudden abnormally high voltage (the lightning surge) from flowing into the battery. However, at a railroad crossing, the battery is connected by cables to devices such as barriers, alarms, and control equipment. If lightning strikes nearby, then the voltage can flow directly into the battery through those cables.
To enable the batteries to withstand such surges, modifications were applied to the battery's control infrastructure from the development stage. Additionally, before moving to the trial stage at a railroad crossing, JR East, 4R Energy Corporation, and third-party testing institutions conducted a variety of operational tests. In addition to the Atago railroad crossing, there are plans to test the batteries at other railroad crossings on the Jōban and Mito lines. These tests will analyze the effect of lightning surges and other environmental factors on batteries across a wide range of areas.
The current electrification wave is propelling us closer to our goal of carbon neutrality. As the use of EVs becomes ever more widespread, the availability of reusable batteries will also increase. Until recently, the idea that EV car batteries could be reused in electrified train crossings was unheard of. And the potential for used EV batteries doesn't stop there. There are numerous other ways to repurpose the batteries for use in a safer, more sustainable future society.
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