Forget the ESV. Use an inexpenive digital multimeter. A flashlight bulb makes a wonderful load and you can see, as well as measure what is taking place.

Nice page on the R/C Battery Clinic for those of you not as veresed in electronics. It's down on the left side of the page, entitled "loaded digital voltmeter, better than an ESV". http://www.rcbatteryclinic.com/