It is a uninterruptible power supply (like in computers to back up in case of power failure) but it is powered by a car battery and thence the time is longer

I'd call it the battery run-time:

See especially this.

"The car battery extends the run-time."

It is a uninterruptible power supply (like in computers to back up in case of power failure) but it is powered by a car battery and thence the time is longer

I'd call it the battery run-time:

See especially this.

"The car battery extends the run-time."

It is a uninterruptible power supply (like in computers to back up in case of power failure) but it is powered by a car battery and thence the time is longer

I'd call it the battery run-time:

See especially this.

It is a uninterruptible power supply (like in computers to back up in case of power failure) but it is powered by a car battery and thence the time is longer

I'd call it the battery run-time:

See especially this.

"The car battery extends the run-time."