San Francisco, Jun 28 (IANS): Tesla CEO Elon Musk, who invests over 90 hours a week to keep his electric vehicle (EV) company from dying, celebrated his 48th birthday on Friday working.

While interacting with his followers on micro-blogging site Twitter, the tech moghul revealed that he was not taking any time off for partying.

"Working on Tesla global logistics," Musk tweeted in reply to a user asking him his celebration plans.

However, most of his 27 million followers advised him to cut himself some slack and gift himself a break on his birthday.

When a user wrote, "You need time off too, don't you? (Yesss... even you)" to Musk, the multi-billionaire entrepreneur replied with a sad face smiley.

Another user wrote: "Happy birthday Elon! You are a big inspiration for the young generation. Keep delivering your innovative ideas and ignore the toxic people."

Maye Musk, the entrepreneur's dietitian-nutritionist mother, also wished her son on Twitter along with a bunch of emojis.

"Happy Birthday @elonmusk! Thank you for 48 years of joy and excitement. Maybe too much excitement. Love Mom," she wrote.

Later, the tech enthusiast posted an appreciative tweet on his handle, thanking people for their birthday wishes. "Thanks for the happy birthday wishes!" he wrote.

After getting done with "the most difficult mission" for his space company SpaceX, Musk has shifted his focus back to Tesla and has been pushing employees to hit the second-quarter delivery goals.

The tech moghul is known for over-working. Previously on several occasions the billionaire has mentioned that sometimes he puts in 120 hours in seven days to keep Tesla functioning smoothly.

In his own words, he has described the schedule "excruciating".

However, he "hopes to reduce (work) to 80 hours next year", he had said in an interview.