The WS-2902A sensor array has the following 3 power solutions:
- Solar panel to power the sensor array during the day and to also recharge a super capacitor.
- A non-removable super capacitor. This is like a rechargeable battery but it charges much quicker, but it is only good for a shorter duration than a typical rechargeable battery. Its purpose is only to power the sensor array during the night as it will be recharged the next day. On some very cloudy days it may also power the unit during the day.
- Regular user replaceable AA cells. It is recommended that the user install Alkaline batteries or in very low cold climates it is recommended to use Lithium cells as they perform better at very low temperatures. Do not use rechargeable batteries as there is no benefit. A good Alkaline or Lithium set will last you 2 or 3 years. If you use rechargeable batteries you'll spend more and negate the benefits that you would have gained with Lithium for the price, and with rechargeable batteries you'll still need to replace them because they don't last but 2 or 3 years anyway, and you'll have the aggravation of needing to pull them out and recharge them. So there is no benefit to rechargeable nor in cost nor in performance in cold nor in replacement time nor in ease of being worry free so that it doesn't require recharging. The purpose of these Alkaline or Lithium batteries is to power the sensor array when the super capacitor is not sufficient because of extended days of cloudy coverage where the solar panel cannot recharge the super capacitor.
If you find that you are needing to replace the batteries after only a few months then you probably have your sensor array in a bad sited location of too much tree cover with not enough direct sun. This will also affect your solar radiation and UV reporting. Those trees are probably affecting everything...wind...temp...etc. Either that or you live in Alaska and it is winter and only get 4 hours of daylight and your batteries are being over-utilized.
I live in Florida and I could most certainly get by with regular Alkaline batteries as it hardly ever gets below 30°F but I went through the added expense of Lithium for piece of mind.
If you still decide for whatever (bad) reason to use rechargeable AA batteries know that the solar panel will not recharge them. The solar panel only recharges the internal non-removable super capacitor. The super capacitor is also referred to as a supercap.