A dead battery in the middle of a voicing job costs you time, and maybe the client's confidence. One charge lasts roughly four to five pianos, which covers most days, but you never know when a long day or a surprise second instrument will come up. A spare keeps you working while the other charges.

Keep one in your tool case and you're covered:

• Swap batteries in seconds and keep voicing

• Never cut a job short or reschedule a client

Be the technician who's always prepared.