If you are tired of replacing batteries in your portable radio or in any other battery-powered device, using an AC power adapter is a good alternative. All you need to do is to determine the voltage(V) and current (mAh) of the device. Then, attach the appropriate adapter to the place where the batteries make contact inside the device.
Remove and count the batteries in the device you're adapting. Standard dry-cell round batteries such as AAA, AA, C or D are all 1.5 volts. Multiply 1.5 by the number of batteries. So, four batteries would equal 6 volts; six batteries would equal 9 volts and so on.
Find the current or amp (mAh) rating either in the specification sheet in the device's manual or on a sticker on the device itself. This value is the current (mAh) for which the adapter should be rated. Using an adapter with a higher mAh value than your device is OK because the device will only use what it needs from the adapter.
Purchase an AC adapter that matches the voltage and mAh you figured out in the steps above.
Cut off the low-voltage connector at the end of the adapter's wires. Strip about a half inch of insulation from the wire's ends and pull them apart about by 4 or 5 inches.
Look into the battery compartment and notice that there are two connectors the batteries touch on either side of the compartment. One side has the two connections tied together by a piece of metal, while the other side has two separate connectors. The adapter's wires will connect to the side with the separated connections.
Identify the neutral wire of the adapter by the white stripe or raised strip on one of the wires. Attach the neutral wire (with electrical tape or solder) to the negative terminal inside the battery compartment. Remember to only attach the wire to the side of the battery compartment where the connections are not tied together.
Connect the positive wire from the adapter to the connector in the battery compartment where the nub of the battery or + normally goes. Again, only connect to the side of the battery compartment where the connections are not tied together.