about their first stop on track this morning
https://www.autosport.com/f1/news/13467 ... -test-woes
It is understood that the electrical issue is related to the battery, but it is unclear whether the problem originates from McLaren's or Renault's side.
McLaren also appears to have been forced to make compromises to its rear bodywork in a bid to help cooling in the car, after it faced overheating headaches during the first test.
Scorch marks on the engine cover last week prompted the team to add an extra cooling slot.
As the car emerged on Tuesday, the team had added three extra slots in a bid to help hot air escape, as Giorgio Piola's exclusive photograph (above) shows.
The slots are not ideal for performance, which could mean the team is forced to tweak the design of its engine cover to help increase airflow and cooling before the first race of the season.