We get feedback from customers getting two years out of a battery. The average should be more than one year but if you aren't getting that and can't explain it due to bad batteries, or cycling the door multiple times a day, or leaving an active alert causing the LED to blink fast and drawing down the battery, then call us so we can help figure it out.
Some customers have looked for rechargeable batteries and chargers and have not found them at the prices we showed where we bought RayOVac brands from Walmart.
But here at our local feed store and ACE Hardware, I have seen prices that are not so bad. For instance, at the Tractor Supply Company (TSC) I took a photo of what they have. $13 for the battery and $12 for the charger (this charger needs to be switched to the 6 volt mode since the charger will also charge 12 volt batteries). But please run your ADOR on 6 volts, not 12 volts.
Before you put the battery in service, it is a good idea to charge it over night. The ADOR1 should use less than 1 AH of energy a year so that is only around 2mAH of energy a day. That is miniscule and even a very small solar panel will be able to replace that energy plus more, every day, so you can see the charger is a big overkill to leave it hooked up all the time.
So here is what I found at TSC:
This charger plugs into a wall outlet or extension cord and has a 6v and 12v setting. I have not tried using this charger and I do not know for sure if it automatically will go to a "trickle charge" mode. A charger designed for temporary hook up may overcharge a battery.
Note that you have your pick of either the tab top or the spring top battery at the same $13 price. Either one works...your preference. They both are supposed to have 4 to 5 amp hour energy capacity.