AA batteries are among the most common. They can have capacities ranging from 450 to 2500 milliampere-hours. These batteries provide a cost-effective alternative to conventional batteries of the same size.
Instructions
Step 1
Before carrying out any operations to charge AA batteries, make sure of the following:
- that in front of you - really batteries, not batteries;
- that the batteries are nickel-cadmium or nickel-metal hydride and not anything else. Remember that the presence of the words "charge", "recharge" or "rechargeable" does not always mean that the device is a battery. They can be part of "not rechargeable", "non-rechargeable", "do not recharge" or similar. These are all warnings that you have a battery in front of you and that it cannot be recharged.
Step 2
Look for the capacity mark on the battery. It is usually expressed in milliampere hours. Convert it to ampere hours. Divide the resulting number by ten. You will get the rated charge current expressed in amperes. For example, the capacity of the batteries is 1500 mAh, or, which is the same, 1.5 Ah. Then the charge current is 0.15 A.
Step 3
It is most rational to charge AA-size batteries not in pairs, as is usually done, but one at a time. Use a power supply for this with an output voltage of 3 V.
Step 4
In series with each of the batteries to be charged, connect a resistor, the value of which is calculated as follows. Since the voltage of the discharged battery is 1.1 V and the power supply is 3 V, the voltage drop across the resistor at the start of charging will be 1.9 V. Divide this value by the charging current, expressed in amperes, and you will get the value of the resistor, expressed in ohms. … Towards the end of charging, as the voltage on the battery rises, its charge current will drop somewhat.
Step 5
Calculate the minimum wattage of the resistor. To do this, multiply the voltage drop across it by the charge current. If the latter is expressed in amperes, the power will be in watts.
Step 6
Connect the battery in series with the resistor to the power source in the same polarity as the source itself. Charge for 15 hours.
