# How does battery chargers work?

1. May 23, 2005

### rsnd

I mean do you input a lot of current and it has some sort of capacitor in it to sotore the charge? any links I can make use of?

Thanks heaps

2. May 23, 2005

### _X3R0_

If this is not correct please inform me and im sorry ahead of time. But if i remember correctly from my physics class the way the battery is used up is that the electrons from the negative end are all transfered to the positive end through a chemical reaction. The way you charge a battery is you reverse this process by giving the negative side a stronger positive charge making the electrons want to go back to the other side. To my knowledge there is no energy lost or given just transfered from one side to another. There is a limit to how many times you can reacharge a batter but it is alot and you dotn have to worry about that. Also you could charge every battery but it wouldnt be wise to do it because the battery could explode spewing some battery acid around and That is not a good thing.

3. May 23, 2005

### rsnd

Hmm...how about AC batteries? e.g. If I wanted to store energy directly from an AC generator which is to act as a battery charger?

Thanks

4. May 23, 2005

### SGT

There is no such thing as an AC battery. All batteries are DC.
If you want to charge a battery from an AC source, you must rectify the current. Noneed for a filtering capacitor, since the battery will act as a filter.
If the voltage ofthe AC source is much greater than the voltage of the battery, you will need a transformer to lower the voltage.

5. May 23, 2005

### The Reverend BigBoa

Which is what, in most cases, the battery charger will do. It plugs into the A.C. and then outputs a D.C. voltage, and depending on the quality/expense of the charger, will also allow you to select various "current" ranges. That allows you to either charge the battery quickly, or more slowly. For an example, if it's the type of charger you use with an automotive battery, you might have a low current output of 2-10 amps, a midrange of 25 amps and a "heavy duty" output of 60 amps.

6. May 23, 2005

### rsnd

Well...thats a lot of current you are talking about! Please fix me up if i am wrong or there is a better way of looking at it! So It would not matter about what current/voltage I input to the charger, as long as I input a fare ammount of each over time to make up for the energy I am trying to store for later use!

Thanks a lot!

7. May 24, 2005

### SGT

If you are using an AC source, the amplitude of the voltage supplied to the charger is irrelevant. A transformer can drop the voltage to the value requested by the battery. The output voltage must be superior to the battery voltage in order to charge it, but the excess voltage should not be excessive, or you will damage the battery.
The current supplied to the battery is generally limited by the battery itself. AsBigBoa mentioned, more elaborate chargers, like the ones used in automotive batteries, allow a limiting of the output current and a longer charging time (fast charged batteries have their lifespan shortened).
The current input to the charger is limited by the output current.