Motorists are being urged to check their car batteries before returning to work amid a warning that many could be flat after the festive break.
Halfords said most car owners have not checked the state of batteries for a year, much longer than the recommended three months.
The firm said around one in six drivers aged between 25 and 34 did not know where the battery was located in their car, while half of all motorists had no idea how to jump-start a flat battery.
"It's not just commuters who feel sluggish after the festive period - but their cars too," said Ella Colley, of Halfords.