Here is an idea... Maybe one day, your on a strange ramp somewhere and need a jumpstart. Oh sure, you could jerk the cover off the battery, in the cockpit, run some hot leads down near your feet, and cross your fingers that you don't blow yourself up... Or in the alternative. You could call the FBO and bammoo, your hooked up and running.
Here is a "Cessna" type jack, strategically placed under the oil filler door for easy access. It has a little flip door, held open here, where the plug goes. I happen to have a mig welder and welded some tabs to the engine mount. But you could even tie wrap it to the mount as well.