This falls into the “If You’re Feeling Brave” category, but it could work nicely.

Per The Verge, MacBook Pro user Evan Rodgers took a CCTV battery, a third party MacBook car charger, and some soldering tools to create a do-it-yourself external MacBook battery.

Watch the video, see what you make of it and if you have the parts on hand, you can avoid a fairly costly trip to the Apple Store for a replacement MacBook Pro battery and add about two to three hours of on-the-fly usage: