Range data for Tesla Semi misses Musk’s predictions

Data collected for the first time on the range and battery performance of the Tesla Semi truck has shown that the vehicle has failed to meet the company’s claims of reaching 500 miles on a single charge.

As part of the Run on Less event, a demonstration of electric freight vehicle performance organised by the North American Council for Freight Efficiency (NACFE) and fleet tracking company Geotab, the performance of three Tesla Semis is being measured as the vehicles are used in day-to-day operations by soft drinks heavyweight Pepsi in California.

The purpose of the event is “tracking key metrics of the trucks and the chargers to gather valuable data”, according to NACFE.

The industry has been waiting to see how the Tesla Semi would fare in real highway driveway conditions after the company made bold claims about its range and charging speed. Real world driving conditions can greatly vary a vehicle’s performance based on factors such as payload, temperature, and wind speed.

The highlight of the data from Tesla’s perspective is that the third truck covered 794 miles in one day. This distance was covered in three trips of 165 miles, followed by a 245-mile drive, with a 45-minute stop in between. Finally, after reaching full charge in around 90 minutes, the truck drove for eight uninterrupted hours.

This final journey was the greatest feat of range achieved on a single charge across the three days of the demonstration. The truck drove over 380 miles while finishing the trip with around 20pc of its battery charge.

The previous day, the same truck covered 377 miles but emptied its battery. The next day the same truck covered 188 miles on 52pc of its battery charge.

While these statistics show range capabilities which would largely meet the needs of the freight industry, the Semis have not in this limited testing come close to Tesla’s claims of 500-mile range on a single charge.

However, commentators were quick to point out the lack of information given by event organisers about how much weight any of the trucks were carrying or on what terrain, factors which can significantly affect the battery performance of vehicles.

“The most important data is left out,” says Mike Hoheisel, territory manager for the Pape Kenworth dealership network, adding that “the trucking world needs to see real payload numbers”.

“[It is] very odd that they can give all this information except payload. Trucking companies live on cost for payload,” Hoheisel says.

The event organisers report total payload for the Tesla trucks as “up to 82,000lbs”, but it is not clear if this simply refers to Tesla’s previous maximum estimates for the truck’s fully loaded weight.

Recharging

The data shows that the Semi was able to charge from 19pc to 80pc state of charge in 55 minutes using a 750kw DC charger. Measuring the time taken to charge up to 80pc is a more useful metric than the time taken to reach full charge, as charging speed slows considerably as the battery approaches full state of charge, and routinely charging to 100pc risks degrading the battery.

A charging speed like this comes close to the target of the anticipated megawatt charging system, which aims to charge class six and above trucks in under 45 minutes.

The charging speed data also allows calculations of the vehicle's true battery capacity, which Tesla has previously claimed as 900kw. “I'm guessing 750-800 kwh [capacity],” says Salim Youssefzadeh, CEO of HDV electrification firm WattEV.

“You can see that Truck 1 drove 335 miles using 77.5pc of the state of charge. At 1.8kWh/mile and a nearly linear discharge, this comes out a little over 750kWh,” Youssefzadeh continues.

The Tesla trucks’ batteries also regenerated considerable levels of charge through regenerative braking on top of the energy regained through recharging. Across the challenge. the trucks repeatedly regenerated charge which amounted to 20-23pc of the total energy put into the battery across the day.

According to data published by the US Department of Energy, 87pc of US domestic freight journeys are below 250 miles in length. Tesla’s range numbers from this limited testing may have fallen beneath Musk’s bold predictions but the initial numbers appear to show the Tesla Semi as a viable vehicle for the freight industry.

The market opportunity for Tesla and its electric truck competitors could be ripe. As Dave Mullaney of thinktank the Rocky Mountain Institute points out, “this type of duty cycle is where traditional diesels fare the worst, both in terms of fuel economy and pollution emissions — with emissions management systems often struggling in low engine load conditions like this”.