There are three possibilities: One, batteries do not like to be cold. At low temperatures (32F) battery life can be one third of that at room temperature (72F). Two, some brands of batteries will not deliver the high currents used in our receivers and 100 mW transmitters. We use Eveready as our standard battery. Three, our units will operate to very low battery voltages and you may not be running the battery down far enough. Here's a reply to a UCR201 user that was replacing batteries every 2 hours or so.
At room temperature, the 201 should give you +4 hours of operation. Try an experiment when you have some free time with a fresh battery. Simply run the unit in the battery voltage display mode and see how long it takes to pull the battery down to 6.5 Volts. The system will operate perfectly to below 6.5 Volts since all internal voltages come from several switching power supplies. We have found a lot of variation in XXXX batteries and some batches will not provide the high currents the 201 draws. We have never found problems with Eveready 9 Volts. The XXXX batteries acted so weird I suspected they might be counterfeit. This was on several batches of XXXXXs from different parts of the country. Further testing found that other XXXXXs were almost equivalent to the Eveready's. We remain puzzled. My advice is that if you are getting short life, try the Eveready's as a standard before deciding the unit is defective.
If you are having short battery life in transmitters due to cold weather, keep the transmitter warm as long as possible before you have to use it. Belt pack transmitters can be also be put under the coat so as to be next to the nice warm human being.Alkaline batteries, though very good at room temperature, cannot deliver much current at lower temperatures. Battery life can be as little as one third normal on a cold day and even less if they cold soak for any length of time. Life can be as little as just a few minutes at -20 F.
If you must use disposable batteries (non rechargeable) then lithium batteries are the only good choice. They have shorter life at low temperatures but are still much better than alkalines.
In the AA battery size, NiMh batteries are a good cold weather choice. At low temperatures they have almost as much life as at room temperature and are rechargeable to boot. We recommend the Eveready NiMh batteries and 15 minute charger that we provide with the SM, SMD and SMQ transmitters. One precaution is that the batteries cannot be recharged if they are cold. They can be used without any problem but must be at about room temperature to be recharged. (See FAQ I don't get much battery life in my transmitters when they are cold. What kind of batteries should I be using this winter?)
In the 9 Volt battery size, NiMh batteries perform as well cold as they do at room temperature but they don't have much battery life (capacity) cold or warm. At one time they were the only choice for very low temperatures but LiPoly rechargeable batteries are now available that have more capacity than alkaline batteries and perform very well at low temperature. They are currently sold under the iPower brand and are available on the internet, from some dealers and from Lectrosonics.