Guide to Charging Battery-Electric Construction Equipment

Incorporating battery-electric construction equipment into a fleet can be a smart way to increase the sustainability of projects and lower jobsite emissions. Opportunities are on the rise as manufacturers introduce more and better models, including larger machines powered by energy-dense batteries. Choosing which categories of battery-electric equipment to buy or rent is the first step. Planning for the charging of that equipment is the next.

Battery charging technology is rapidly evolving. Given the variety of ways to charge equipment, the differences in onboard chargers and plugs, and limitations on the level of charging a machine will accept, the charging question can get complicated. The best approach varies depending on whether the jobsite is connected to the grid, what equipment you’re charging, and how you’ll be using it (for example, whether your operations allow for overnight charging).

To get a handle on basic charging considerations, start with this guide. For more help with choosing a charging strategy, consult a full-service rental equipment vendor that offers electric construction equipment, such as United Rentals. They can help you assess your charging needs based on the equipment you rent, your jobsite, and the charging speed you need.

Identify a power source

Whether you’re charging the machine’s batteries through the onboard charger or using an offboard charger for faster charging, you’ll need a source of power.

Grid power: Level 1, 2 and 3 charging

If the jobsite has grid power, that’s the obvious solution, though you’ll have to bring the machine back to the power outlet each night.

In most cases, 220/240V power (Level 2 charging) is the optimal choice. It’s the same type of power that clothes dryers and electric ovens in homes use and will fully charge most battery-electric construction equipment overnight. Typically, all you need is a compatible plug to connect the onboard charger to an outlet.

It's possible to charge some equipment with a 120V outlet (Level 1 charging), but the charge time will likely be double that of a 220/240V connection.

Level 3 charging, also referred to as DC fast charging, uses a DC current. A Level 3 charger can charge electric construction equipment much faster than Level 2 charging—in as little as one or two hours, depending on the battery size—and may be worth considering for large projects that utilize the heaviest electric machines. Level 3 charging requires a specialized charger that is typically connected directly to the electrical grid, and purchasing and installing one can be prohibitively expensive, especially for smaller jobsites. Mobile DC chargers are also available.

Remember that a machine will charge at the fastest rate its battery accepts and no faster. Machines with smaller batteries may accept only Level 1 or 2 charging, not Level 3 charging. Charge times depend on both the charger output and the battery input capacity. Either one may limit the charge speed.

Mobile power generation options

When grid power isn’t an option, you’ll need a mobile power generation solution such as a generator or stand-alone battery.

Relying on diesel generators arguably defeats the purpose of using electric equipment given their greenhouse gas emissions and noise. Lower-emission alternatives include propane/natural gas generators and hydrogen fuel cell generators. Hydrogen fuel cell generators produce zero emissions, but they make sense only in locations where hydrogen delivery is available. They are more expensive to rent and operate than other choices. To maximize the environmental benefits of a hydrogen fuel cell generator, consider how the hydrogen was produced.

Large, stand-alone battery packs such as the POWRBANK may be another viable solution, depending on the equipment’s power needs. With mobile battery solutions, you can bring the battery to the machine instead of bringing the machine to the power source. Some of the largest batteries will charge an electric mini excavator with a battery capacity of 24kwh in about 8 hours with Level 2 charging.

If you go the route of using portable batteries, there’s a quick formula to estimate what size you need. Multiply the size of the equipment’s battery in kWh by the number of days you want to run it, then multiply that figure by 20%. For example, if you have a 25kWh battery and you need to run the machine for two days, a 120kWh standalone battery should provide the required energy.

Ascertain the charging speed you need

For one-shift operations, overnight charging with a Level 2 stationary or mobile charger should be sufficient. Most battery-electric equipment can be fully charged in 5 to 10 hours at Level 2 charging. A higher-amperage Level 2 charger provides faster charging.

Smaller equipment may be sufficiently charged overnight with Level 1 charging.

If needed, the equipment’s batteries can be topped off during breaks with a Level 2 or Level 3 charger. These battery top-offs, known as opportunity charging, can be as short as 10 to 30 minutes.

For two-shift or multi-shift operations, you’ll need faster charging to keep the equipment in heavy use. Look to a higher-amperage Level 2 charger or a Level 3 charger.

Understand run times

How heavily and how continuously you use the equipment influences daily battery depletion and will affect the power setup you need. Running out of charge in the middle of a task is not ideal when you’re trying to complete a job on time. Draining the battery completely is also bad for the battery.

OEMs typically estimate daily use as anywhere from 4 to 6 hours of work. The battery will last longer than that with light-duty applications. Heavy-duty applications, cab heating or cooling, and cold ambient temperatures cause batteries to discharge faster.

Because electric equipment doesn’t idle, these machines have significantly less active operating time during a shift than diesel machines do, so 4 to 6 hours of battery power is often sufficient for an 8-hour shift. If it isn’t, plan for opportunity charging during breaks and between shifts.

Seek professional guidance

As manufacturers continue to market new battery-electric aerial lifts, material handling equipment and earthmoving equipment, these machines will likely play an increasingly large role on indoor projects and projects with emissions targets. Currently, battery-electric equipment is most convenient to use on jobsites that are connected to the grid, but as battery technology and charging technology advance, this may change.

Understanding the charging options for a particular piece of equipment can be challenging. United Rentals can help guide you to the right equipment for the task and can also advise on the most effective charging solutions for your jobsite, application, and budget so the equipment is always ready when you need it.

Visit our online marketplace to browse our vast inventory of equipment or call or visit your local United Rentals branch to inquire about electric equipment rentals.