science

SAE J3105

SAE J3105 is a science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand SAE J3105 rather than just read about it. In short: SAE J3105 is a recommended practice for automated connection devices (ACD) that mate chargers with battery electric buses and heavy-duty vehicles. The practice is maintained by the SAE International with the formal title "Electric Vehicle Power Transfer System Using Conductive Automated Connection Devices Recommended Practice", and was first issued in January 2020.

Key takeaways

SAE J3105 belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect SAE J3105 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of SAE J3105 from memory before moving on to harder problems.

Reference excerpt

SAE J3105 is a recommended practice for automated connection devices (ACD) that mate chargers with battery electric buses and heavy-duty vehicles. The practice is maintained by the SAE International with the formal title "Electric Vehicle Power Transfer System Using Conductive Automated Connection Devices Recommended Practice", and was first issued in January 2020. It covers the general physical, electrical, functional, testing, and performance requirements for automated conductive DC power transfer systems intended for heavy duty vehicles, focusing primarily on transit buses. J3105 defines a common automated conductive charging system architecture so that any vehicle selecting one of the supplemental specific ACD implementations can use any charger that complies with that specific implementation, regardless of manufacturer, similar to how the earlier IEC 62196, SAE J1772, and SAE J3068 standards define the characteristics for a manually-plugged electric vehicle supply equipment interface.

History SAE formed the Medium and Heavy-Duty Vehicle Conductive Charging Task Force in 2016 to develop a recommended practice for heavy-duty electric vehicle conductive charging. Participants in the Task Force included transit bus manufacturers (Gillig, New Flyer, Nova Bus, Proterra), charger manufacturers (ABB, Heliox, Opbrid, Siemens, Toshiba), interface manufacturers (Furrer+Frey, Schunk Group, Stäubli, Stemmann), electric utilities (EPRI, SMUD, SCE), transit operators (APTA, CTA, King County Metro, LACMTA, NYCTA), and interested parties (ANL, CalStart, CEC, CTE). The Task Force first published the SAE J3068 recommended practice in 2018, building on work from existing international standards for charging using three-phase AC power. J3068 defines a manual Type 2 connector that can be used for both AC charging or DC charging up to 1000 V.

General design characteristics Transit operators may use opportunity charging (OppCharge) to extend the range of electric buses while stopped on a layover. This is in contrast to depot charging, where the buses are charged at a common garage or storage facility while out of service. An ACD system may be used for both opportunity and depot charging. For instance, the Schiphol Airport bus depot has overhead chargers at both 30 kW (depot charging) and 450 kW (opportunity charging) for its all-electric bus fleet. J3105 defines two current levels of DC charging, with supply voltage from 250 to 1000 V:

Up to 600 A (350 kW) Up to 1200 A (1200 kW) These levels are mutually compatible; for instance, a Level 1 vehicle could connect to a Level 2 charger and would receive an appropriate amount of power. Specific requirements for the charging station and communication are governed by IEC 61851-23 and ISO 15118. When a vehicle approaches a charger, wireless communications via IEEE 802.11n will pair the vehicle and charger. The initial communication will be used to guide the vehicle's driver to an appropriate position so the connection can be made, and communications will go through the Control Pilot interface after the vehicle is connected.

Only four interface connections are defined by J3105. The specific physical interfaces are defined in the supplemental recommended practices.

+ DC Power (+) – DC Power (–) PE Ground / Protective Earth CP Control Pilot

Specific charging implementations J3105 includes three supplemental recommended practices for specific ACD implementations:

J3105-1 "Infrastructure-Mounted Cross Rail Connection" (or "Cross rail"): the overhead charging station extends contacts down on a pantograph to meet roof-mounted vehicle rails J3105-2 "Vehicle-Mounted Pantograph Connection" (or "Bus up"): the vehicle extends a pantograph up from its roof to meet overhead charging station contacts J3105-3 "Enclosed Pin and Socket Connection": the charging station extends a pin horizontally into a vehicle's roof-mounted socket The physical characteristics are described in the specific ACD implementations. Each of the recommended practices for specific ACD implementations includes the conductor dimensions and spacing, and the required alignment and connection procedure. A small amount of misalignment is tolerated, depending on the specific implementation:

Notes

Cross rail (J3105-1)

In the cross rail ACD implementation (officially, "Infrastructure-mounted Cross Rail Connection"), a curbside charging station includes an overhead structure overhanging the street. After the bus pulls up to the charging station, contacts are lowered from the overhead charger on a pantograph and connect to rails mounted on the forward roof of the bus. The cross rail implementation is marketed commercially as OppCharge (opportunity charging) and the OppCharge consortium, led by Volvo Buses, includes several bus and charging infrastructure manufacturers. The first OppCharge station was deployed at the end of 2016 in Bertrange, Luxembourg by ABB for hybrid buses built by Volvo. In the United States, the first OppCharge stations were deployed in 2019 by New Flyer Infrastructure Solutions as on-route chargers for the New York City Transit Authority along its M42 route.

Bus up (J3105-2)

The bus up ACD implementation (officially, "Vehicle-mounted Pantograph Connection") also uses an overhead charger, but the charging contacts remain fixed in place while the bus extends a pantograph up from its roof to meet the charger. The charging contacts are on the underside of a long hooded enclosure to facilitate the bus and charger contact connection. The bus up implementation has been adopted by VDL Bus & Coach using chargers provided by Heliox, with both companies based in The Netherlands. The Amstelland-Meerlanden charging depots at Schiphol Airport were the largest electric bus charger installation in Europe when they were completed in 2018, including 23 450 kW opportunity chargers and 84 30 kW depot chargers from Heliox, servicing a fleet of 100 VDL Citea SLFA articulated buses equipped with bus-up pantographs. Heliox also introduced a dual-interface system compatible with both top-down (J3105-1) and bus-up (J3105-2) vehicles in 2018.

Pin and socket (J3105-3)

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with SAE J3105

Start with the simplest possible case. Write down what SAE J3105 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to SAE J3105 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about SAE J3105 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of SAE J3105

In research: SAE J3105 appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses SAE J3105 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: SAE J3105 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Automotive standards, Charging stations, International Electrotechnical Commission, so understanding it makes those chapters shorter.
In everyday life: Look for SAE J3105 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study SAE J3105 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what SAE J3105 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain SAE J3105 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is SAE J3105 in simple terms?

Why does SAE J3105 matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study SAE J3105?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on SAE J3105.