Recharging alkaline batteries

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.

Introduction

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.

afety

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.

How It Works

As an alkaline battery is discharged, chemicals inside the battery react to create an electric current. However, once the chemicals have reached chemical equilibrium, the reaction stops, and the battery is "dead." By exposing the battery to another electric current, equilibrium can be shifted backwards towards the original reactants, making it possible to reinstate electric charge to the battery.

The Math

Gathering Data

The voltage and capacity of the battery in ampere-hours is required before charging and can normally be found on the battery or cell casing. Specifications of the power source used for recharging will also need to be known, which can be found on the power adapter being used. There is a section for input, tip configuration, and output (the one we want). Voltage and the current are important.

Plugging-In the Numbers

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.

Q/I=T

Where Q is capacity in mAh, I is current in mA, and T is time in hours.

Longevity

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.

ee also

*Alkaline Batteries
*Rechargeable alkaline battery
*Electricity
*Potassium hydroxide
*Power Supplies

External links

* [http://www.afrotechmods.com/reallycheap/batteries/batts.htm Afroman's guide to recharging alkaline batteries] - Personal Experimental Data - Contains Strong Language, however Technically Accurate
* [http://www.i-hacked.com/content/view/207/44/ Charging the unchargeable] - Improved alkaline charging circuit
* [http://www.jtbaker.com/msds/englishhtml/P5884.htm Potassium hydroxide MSDS from JTBaker]