Stoffel Vandoorne has expressed some concern as a difficult winter for McLaren continues.
After a troubled opening test, the British team's new Renault-powered car struck more problems in Barcelona on Tuesday.
Some of the blame might be Renault's, with Red Bull also suffering from a battery problem.
"This is a normal process," argued Renault's Bob Bell. "We're using all the batteries in testing and choosing the best ones for the rest of the season."
Yet as images emerged of the 2018 car featuring emergency cooling at the top of the engine cover, McLaren driver Vandoorne admitted some concern.
"It's true. It was a very difficult day for us," he told Belgian broadcaster RTBF.
"We had a lot of technical problems and now we have to find solutions. We have only three days of testing left and we need this preparation for Melbourne."
McLaren boss Eric Boullier insisted that he is not "overly concerned" about the problems.
When asked if the Renault battery issues at McLaren and Red Bull were a worry, Renault works driver Carlos Sainz admitted: "Of course, and we must carefully study what happened to them.
"If they are related to the Renault engine, we will deal with them."
The season proper gets underway with the Australian Grand Prix on March 25.
