Battery Sizing Key First Step in Electric Vehicle Development

When OEMs are developing electric vehicles, they must consider what battery size is needed as early as possible in the design process to avoid costly customizations or alterations.

This compilation of frequently asked questions (FAQs) presents a brief overview of the considerations necessary to design an electric machine, focusing on battery selection, duty cycle determination and voltage requirements. 

What is the first step in an electrification project for new machines?  

A review of the entire vehicle architecture is a necessary first step in many electrification projects. This is true of hydraulic function conversions in mechanical projects or redistributing component locations. Another critical consideration is component sizing — the battery, electric motor, power and charging system should be top-of-mind in an electrification project. 

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What should an OEM consider when selecting a battery?

Determining the acceptable duty cycle for the new machine is key to battery selection. Understanding the energy required will lead to the most appropriate battery selection. Original equipment manufacturers (OEMs) must also calculate battery sizing. The battery comprises up to 50% of the total machine cost, so proper selection is crucial to keeping a project within budget.

How is an acceptable duty cycle determined? 

Typically, designers will begin planning the worst-case scenario duty cycle and then will work backward to determine the best choice. If available, telematics data from traditional machines (engine and hydraulics) can be useful as it gives designers concrete figures to help calculate the duty cycle required. 

When possible, use of operating data from traditional machines can help determine appropriate duty cycles and thus battery power needs for electric-powered versions.

What if telematics data is not available?

This is often the case for machines that previously ran on internal combustion engines, as detailed energy consumption is not typically a consideration. In the absence of telematics data, calculations should be done using the vehicle and application specifications. 

What data should OEMs collect to determine duty cycle? 

Data points such as weight, speed, max grade, auxiliaries and field functions should be collected to create a working point matrix. This matrix can then be used to augment the worst-case duty cycle scenario and ensure that the OEM is not stuck with components that are too large or expensive for the machine, application or end user. 

Are there real-time testing options available once a duty cycle is determined?

Concept machines are an excellent option for testing an estimation matrix against real-time scenarios. These machines often have built-in logging frameworks, providing real-time data to the designers as the machine runs through different duty cycle scenarios. Experienced OEMs should have the capability to provide this type of testing. 

What other considerations should OEMs focus on during this process?

There is often a tradeoff between performance expectations and the packaging constraint of the new machine. For instance, an OEM may start a project with performance expectations that end up not fitting with the battery type that best suits the machine, application or cost. OEMs should be prepared to adjust performance expectations based on real-time test data.

How does battery size affect an electrification project?

In the early days of vehicle electrification, batteries were much more cumbersome than they are today, which resulted in vehicles having to be designed around the battery size. Now, with more sizes available, the design and application usually take precedence.

While many companies specialize in designing batteries, there are costs associated with customizing a battery for a particular application. Even with more sizing options, OEMs must consider what battery size is needed as early as possible in the design process to avoid costly customizations or alterations. 

OEMs must consider what battery size is needed as early as possible in the electric vehicle design process to avoid costly customizations or alterations.

What role does voltage play in electrification? 

From a consumer perspective, we have been “trained” to think that a higher voltage is better. However, this is not an ideal mindset for electrification projects, as it can lead an OEM to make inappropriate battery selections for their machine. Some applications may require a higher voltage, while others may benefit from a reduction in voltage size that is appropriate for its specific usage. 

What is the voltage range seen across industries?

OEMs often aim for a voltage range below 60V. This range is considered safe by international standards, which aims to avoid system complications present in higher ranges. However, this range presents limitations from a power perspective, so it may not be suitable for all machines and applications.

Another standard voltage threshold is 150V. OEMs that can stay below the 150-voltage range have a wider range of vehicle components at their disposal.    

What can OEMs expect in terms of project length/timing? 

Unfortunately, there is no one-size-fits-all answer for electrification projects, as timing varies from one OEM to the next. However, a good barometer for judging timing is to look at the amount of information available. If you have telematics data, your designers already have a head start. Without this data, you will need to budget more time at the beginning of the project before arriving at real-time testing.

Investments such as the usage of third-party companies for system integrations can help to speed up the prototype and testing phases.

What is one piece of advice for OEMs embarking on their electrification journey? 

It all comes down to torque and speed requirements. These requirements should drive component decisions in order to determine what levels of both are required for the specific machine, function and application. Focusing on the torque and speed requirements from the outset will set projects up for success and allow OEMs to arrive at optimal electric designs.

A robust requirement planning phase, combined with in-depth knowledge of the application, will set an electrification project on a successful path. 

This article was written and contributed by Mirko Baggio, director of business development at ZAPI GROUP. He has nearly 15 years of experience in the electric drive industry.

The article originally appeared on Machine Design, an Endeavor Business Media partner site.