Does dual boot harm a laptop battery or reduce its life?

I dual-booted my laptop with Ubuntu 17 and Windows 10 one year back.

After one year, my laptop battery backup has reduced to 40 minutes.

Does having multiple OSes on a laptop harm the battery or reduce its life?

Does having multiple OS on laptop harms the battery or reduces it's life?

As @Akina has mentioned in the comments, no. Having multiple OS on your laptop has nothing to do with battery usage. The laptop hardware uses the battery, not the OS. And on top of that, only one OS is active at a time.

The only noticeable difference you can see is the drivers' quality on Linux. In some of my cases Linux was using more battery than Windows which was caused by low quality drivers. And then again, this isn't a deciding factor for when a battery wears out. Batteries get worn out mostly by age.

Short answer: No.

Long answer: The number of operating systems present in a computer has nothing to do with the battery lifespan. Even if you have a ton of operating systems, only one can run at a time. Therefore, the battery would work the same way it does in a single-boot computer. Batteries naturally wear out with time due to a ton of factors which include but are not limited to:

• Charge frequency
• Age
• Ratio of the time the battery is being used to the time it isn't.

I hope this explanation helps.