You can get the capacitance testers, but by the time you mess around with taking the temperature, getting the pressure right, and having the battery die at the wrong time you will be time, aggravation, and accuracy ahead to get a postage scale, a stack of paper plates,  and a microwave.  Set it up in the feed room or someplace well away from the house; they tend to make a lot of strong odors.  A few times to get a sense of how long to heat the samples and you will be able to get an accurate result in a few minutes.