Recharging Alkaline Batteries is a way of renewing expended alkaline batteries. Although most alkaline battery manufacturers recommend against it, many technology enthusiasts have successfully recharged alkaline batteries.
Ordinary alkaline batteries can be charged with a pulsed charger of a frequency between 40 and 200 Hz, with an on period of about 80% and an off period of about 20%. This must be done to alleviate the possibility of leaking of the alkaline KOH. Not all commercial batteries have the same kind of seal. Duracell batteries tend to show the highest frequency of leaking while recharging. Titanium batteries and other special batteries, such as the Energizer e2, through experimentation appear to only heat up, failing to recharge. In general, a high proportion of alkaline batteries will recharge, but will then self-discharge within a day. Batteries suffering from this effect tend to be identifiable by the heat they generate, even while out of the charger.
Most of the time, attempting to recharge dead alkaline batteries will result in rupture and leakage of aqueous potassium hydroxide. Potassium hydroxide exposure to skin or certain materials, such as fabrics, may cause damage, so caution is advised when handling. Safety goggles in experimentation with recharging ordinary alkaline batteries is advised, taking into consideration that chemicals within the battery can cause severe eye injury, including loss of eyesight. Ruptured batteries are not advised to be disposed of in ordinary garbage due to the fact that the chemicals they contain are a potential environmental hazard.
When recharging batteries, such as four double A's, which hold about 2850mAh of charge, each battery has a potential of 1.5 volts. When putting these four batteries together in a series circuit, the voltage of each battery added together gives a total voltage of approximately 6 volts. In a parallel circuit, the voltage would have only been 1.5 volts.
When attempting recharge, the batteries' voltage must match that of the adapter, which is in this case 6 volts. To determine how long to charge the batteries, the capacity of the battery in ampere-seconds, or coulombs, divided by current of the power source in amperes is the amount of time in seconds in order to charge the batteries. However, if "seconds" is replaced in the equation with "hours", and the "mili-" prefix is placed on the capacity and the current, a more practical value can be derived.
Even though it may be possible, most alkaline batteries are not designed to be recharged, and are intended for only one time use. It is not advised to attempt recharging alkaline batteries since they may eventually give way and potentially release potassium hydroxide in a number of forms. The leaking chemicals are hazardous to people, and also corrode the equipment.