Testing at the Circuit Ricardo Tormo in Spain was postponed following a battery fire in the garage of battery supplier WAE (formerly known as Williams Advanced Engineering) on Tuesday afternoon.
Following an investigation by the FIA and WAE, which concluded that “none of the [other] batteries present the same type of symptoms as the unit that failed”, testing resumed on Thursday afternoon and across Friday with no issues.
Di Grassi, who has returned to the Abt Cupra team this season, praised the reaction to the incident by emergency crews as well as the FIA for updating drivers on the ongoing situation.
“I was very relaxed about what happened to be honest,” he told Autosport.
“I think the track record of Formula E having one battery fire in 10 years of existence, it's amazing.
“It's much better than any combustion racing series had in the past, including Formula 1. So I think that's not a problem at all having one event like this.
“The reaction from Formula E, it was amazing. In 20 minutes, everything was concealed, everyone was evacuated, the fire was contained, it didn't spread out.
“So the reaction was amazing and I felt 100% safe inside the car driving, knowing what happened before and I was perfectly safe driving the car for the next two days.”
The incident was the first major issue with a battery since the all-electric championship was introduced in 2014.
As a precaution, power usage was limited to 300kw for the remainder of the test, while fast-charging pitstops were conducted at a lower voltage.
The FIA also confirmed that the batteries used at testing last week, and which will go back to WAE prior to the season opener in Mexico City, were the same specification as used last year in all 22 cars, which was also the first year of the Gen3 machine.
“We are at the edge of battery technology there with these batteries being able to recharge at 600kW, so I don't think there is any other battery in the world that has this capacity,” added di Grassi.
“When you're pushing boundaries of technology, these things happen, so I am not worried at all.
“I think the season is going to go as planned and everything is fine. I was probably the most relaxed, but that's just how I am. I think all the measures were done in a proper way.”
Porsche’s Antonio Felix da Costa echoed di Grassi’s comments on pushing the boundaries of batteries, and that the incident would provide valuable data moving forward with regards to EV technology both in motorsport and on the road.
“I don’t think we should be here trying to find stories and criticise Williams or Formula E or electric cars,” he told Autosport.
“I think it’s not about that it’s about one car stopped on track, that battery was being looked into and it happened.
“And if anything, it can even be a positive thing, we’ve finally found a way to make a battery catch fire after 10 years and it’s only going to make every electric car on the road and on the race track more safe for the future.”
