After making my purchases I headed home to compare them. (If you have a nine volt battery nearby, you may want to go get it because it will help you in learning the proper evaluating techniques.) First note its vintage. The vintage can be found printed on the side of the battery and sometimes also on the package that it comes in. The vintage is expressed as a month and year in the future. The later that date the fresher the battery and freshness can make all the difference.
Second, note its presentation. Does it have a classic look or a high-tech look? Would you be embarrassed if the repairman saw this particular battery in your electronic equipment when you take it in for servicing? Mom was right when she said, "Make sure you've got on clean underwear and are carrying respectable batteries in case of an accident!" Imagine the shame of dropping your highly valued electronics and arriving at the repair center to find that you had installed a generic battery. Your entire family would be shamed for generations to come.
Next, note the aroma. If the battery has a pleasant bouquet, throw it out! Batteries aren't supposed to smell, so no matter how much you enjoy the aroma, that has to be a bad sign. Keep in mind, this may be a sign of an expired vintage.
Now that we have filtered out some potential losers, we are no ready to begin testing for real. If you have not yet done so, remove the battery from its package. Grab it in the middle of the widest side with your index finger and thumb and pick it up. Hold it so that the positive side, the smaller of the two connections, is on the left. Now open your mouth, stick out your tongue and press the batteries against its tip. Hold it there and savor it. Note its balance and body. Note whether it is sweet or dry. Evaluate its acidic and tannic qualities. If you are testing several, you may find it helpful to write down your notes so that you can compare them all again later.
Since batteries do not leave an aftertaste you will not have to rinse your mouth between testings. However, if you are testing exceedingly fresh batteries or batteries larger than nine volts, you may have to test on multiple parts of your tongue to avoid previously burned areas. Remember, as mentioned before, batteries have no bouquet, so if you notice a bouquet of burning flesh, it's not the battery. I will now share with you my opinions on the batteries that I purchased.