What is a “dead” battery?
Because most of our solar kits for any application use rechargeable batteries that are charged externally using a solar panel, the question of what constitutes a “dead” battery often comes up. Batteries only store power, and over time their capacity to hold this energy naturally decreases. A battery is only branded as “dead” when it is no longer able to be recharged.
Another thing to note is that most appliances will require a minimum voltage to run, which means the battery does not have to be completely drained for the appliance to stop working. Brand new alkaline batteries produce around 1.5V but as the battery slowly becomes depleted, the voltage the battery produces will drop as well. A battery that drops to about 0.8V is normally considered depleted (not at 0V) and will no longer have the ability to power most things.