I just remembered as I was taking my bath & soaking with a pint of my Colloidal Silver in it, that I neglected to answer your question about battery life.
Three batteries strung together initially gave me 28 volts. After a couple of quarts I measured a voltage drop to 27 after about 1 gallon's worth. After that voltage dropped more slowly because I learned quickly to use 27 volts ONLY as an initial kickstart level to get the electrolysis going using pure distilled water, this of course saves a lot on battery life. Been making this for a year or so, been through a half dozen Energizer brand batteries.
Another point you will find useful: keep a real close on the water & learn the time to color change in the water. Just before the water turns to light yellow, it will become white cloudy first. This white cloudy will change to yellow overnight, which is not the most ideal for internal consumption. Keep a hand log next to your electrolysis station & record every change you see versus the number of batteries you are using. The critical thing is knowing how long till a white cloudy appearance shows up, then you some idea when to cut short that time to prevent the colloidal from turning yellow & going over 20 ppm.
After you have mastered keeping your water from turning color, you can test it to be sure you have ionic colloidals present. Put a few tablespoonfuls in a glass & drop a few grains of salt into it, it should turn white cloudy in color, if it does you have at least 5 ppm colloidals.