What is the difference between battery chargers and power adapters?

In many cases, they are interchangable but the terms are used rather loosely at times.

In order to charge a battery, you need to have a charging voltage that is at least slightly higher than the voltage of a fully charged battery. Stand alone chargers that are intended for charging NiMH cells may have timers, peak voltage detectors, or temperature sensing circuits that will shut down the charger once the battery is full.

An adapter that plugs into the device that uses a rechargeable battery will not have the charge monitoring circuitry. Those functions will be handled by the device itself, i.e. a cell phone, laptop computer, MP3 player, or GPS. Those adapters are sometimes also called battery chargers eventhough they often provide power to the device and charge the battery at the same time.

I have a rechargeable flashlight that uses an adapter that is significantly higher than the battery voltage. It will not provide enough current to power the bulb. The charge controlling circuitry is in the flashlight so the charger is technically an adapter. There is switching arrangement that ensures that the bulb is never connected to the adapter so technically the adapter is a charger.

Clear as mud?

Don

To charge a battery, an over voltage is required. Driving current backwards from the normal direction is what actually does the charging. With an equal or lesser voltage, the battery will never charge or continue to be drained.

For example, to charge a 12 volt battery, you might apply 15 or more volts to it. Once the current drops to a certain level, the battery is considered fully charged.

Some power adapters will also charge an internal battery. The device is capible of adjusting the higher input voltage when connected to the adapter with voltage regulators and still apply the higher voltage to the battery to charge it.

Adaptor Vs Adapter

Adapter Vs Adaptor

You might be leaving out some information, but I think this is the answer.

If you have a device (an electric razor, for example) that has a built-in 5V battery, a battery charger will charge the battery and then you can unplug it and use it. If it was a plug-in only razor that needed 5V to operate, the power adapter converts the 110V coming out of the wall socket to 5V for the razor to run on.

battery charger charges the current battery you have. Battery adapter replaces what you have, and it does not contain a battery within it.