Yes, lithium batts are the only ones available for the Opti. As I remember, when I called in about batteries, they said that ALL C123 are lithium. Some of this battery format is in rechargeable NiCad, though. These will only last about 5-10 uses so are not recommended.
Lithium batts can run the Opti at ranges between -20C and around 60C. but reductions of power output, internal resistance, etc, cause shortened battery life. My recommendation for the Opti: (besides always using Lithium batteries)
1) Keep it in an internal pocket. This will keep it well above freezing. During use, internal resistance and discharge chemistry will keep the batts warm even at very low (-10F) temps.
2) Avoid using them for more than 4 uses in a row. Internal resistance will go down but the timing means more electricity for the time when good and warm (above 110F.)
3) Always flip one battery after use (two batteries for the Classic at opposite corners.) All electronic switches require a trickle current to detect which state they are in. However, they all require a an initial “charge” when turning them on for the first time. This roughly cancels out over about an hour of idle current draw. For me, I only use them a few times during the day, so flipping one battery essentially turns this trickle off. You save about a half of a use each night. At night, always flip the batt. Some people recommend a thumb screw glued onto the cap screw but I just use my thumb nail. For the average of 4hr between uses gives me another five or more uses at the end of the battery life.
4) As with all electronics, avoid getting them wet. While sealed, I have had a bit of trouble with condensation corroding contacts. A pencil eraser will polish the contacts clean again.
5) Get in the habit of warming up the batts/Opti before use. They function quite a bit more reliably and easily at body temp usually saving some power. Usually about another use or two over the lifetime of the batts, especially in the morning of a cold day. If the batts are seemingly dead, you can often get another use out of them by warming them over the stove. WARM not hot. This can result in a burst battery of you over do it. Use caution.
5) Always store the batts flipped or out of the Opti. While lithium batts don’t leak, it is just good practice.
Anyway, you can save about 10%-15% of the battery life, more in cool weather(below 40F.)
Wide Mouth Bottles? Just reuse a Gatoraid or Life Water 500ml bottle. For the Opti, it lets it set on the rim as you rotate it gently through the water. They are not deep enough to cause problems, but some rotation is being wise. A 1L bottle is a bit too deep, soo, use a steady rotation on these throughout the treatment. The majority of the UV is produced at the sides of the Opti, soo, By rotating it around a bottle rim provides agitation, it also increases the amount of UV/cm of water depth.
Never use these in floppy water bottles. A crease can cause blind spots to UV and/or low circulation. I haven’t tried the newer Quantum.
I always wipe the cap and rim with my bandana after each treatment. Is this really necessary? I don’t know. But, it seems like a safe practice to me.
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