My cellphone/PDA AC charger says 5V/1A output.

It did not come with a car charger, nor do the stores have one available yet for this model (Cingular 8125)

What if I were to use a car charger from a different cellphone (Motorola RAZR) that was 5V/500mA?

I know that the important number to focus on is the voltage.  How does the different amperage change things?

What about the other way around - Can I use a 5V/1A output AC or Car charger on the Motorola RAZR that comes with a 5V/500mA charger?

Basically, I'm wondering if I will damage either phone with either charger option provided that I don't go over 5 Volts?

If you sue the 1A charger on a 500mA phone, you will most likely fry the phone.

If you do the opposite, it most likely will not work.

My .223....

Quoted: If you sue the 1A charger on a 500mA phone, you will most likely fry the phone. If you do the opposite, it most likely will not work. My .223....

Not quite correct.

You could use a 5v/200A adaptor and it would work just fine.  All the aperage rating means on the adaptor is how much current it can handle.  The device will still only take what it needs.

It might not work because 500mA is only half of one amp.

Think of it like this… Voltage is the pressure and amperage is the volume. If you plug it up to something with too high a voltage then the high pressures can, and will, burn out the circuitry. Just like hooking 100psi plumbing to a 200psi source.

But if you plug it up to something that can’t provide enough amperage (current) it would be like turning on all the water in the house while you are taking a shower. Not enough water can come in to meet demand and the pressure (voltage) drops.

Plugging the device up to something with a higher amperage rating but the correct voltage won’t hurt a thing. So if you find an adapter that’s 2 or 3 amps then you should be fine.

In fact, it’s possible that the adapter you have has a higher output than necessary. I wouldn’t want to risk it because if you pull too much current then you could overheat the adapter.

Some adapters are AC and some are DC and that part has to match too. Batteries are DC and house current is AC. Check that part, because it probably won’t work if you try to send DC power into something designed for AC.

BTW, Power (watts) is how much work that the electricity is capable of. You can determine that number by multiplying the voltage and the amperage.

5V x .5A = 2.5 Watts
5V x 1A = 5 Watts

So of you see a 5V, 5W (or higher) adapter with no current rating then it will work too.

Quoted: Quoted: If you sue the 1A charger on a 500mA phone, you will most likely fry the phone. If you do the opposite, it most likely will not work. My .223.... Not quite correct. You could use a 5v/200A adaptor and it would work just fine.  All the aperage rating means on the adaptor is how much current it can handle.  The device will still only take what it needs.

Great, this is just what I needed.  More confusion!

So then which is it?  Does that Amperage matter?  Does using a 500mA charger on a phone that can handle a 1A charger mean that it wont work, or that it will charge more slowly, or will it make any difference at all?

And using a 1A charger on a 500mA phone will fry it???  

Quoted: Quoted: Quoted: If you sue the 1A charger on a 500mA phone, you will most likely fry the phone. If you do the opposite, it most likely will not work. My .223.... Not quite correct. You could use a 5v/200A adaptor and it would work just fine.  All the aperage rating means on the adaptor is how much current it can handle.  The device will still only take what it needs. Great, this is just what I needed.  More confusion! So then which is it?  Does that Amperage matter?  Does using a 500mA charger on a phone that can handle a 1A charger mean that it wont work, or that it will charge more slowly, or will it make any difference at all? And using a 1A charger on a 500mA phone will fry it???

Think of it this way:
The current rating on the source is how much power it can deliver.
The current rating on the end device is how much power it may need.

Therefore you want the supply's amperage to be >= the end device's rating.

Make sure the polarity is correct, usually on the label stuck to the charger.
If it's not right you can easily fix it by cutting the wires and swapping the leads.
It should be fine for charging it but probably not for running it.

You wont harm your phone with this charger, chances are it will not work, It may say charging but the funny little chip in the phone that controls battery functions will not let it pass. I ran into this problem with my razor. Its CDMA and I bought a GSM charger. Looked like it was charging but the GSM charger did not put out enough Amps on in this case or yours, only 1/2amp.

Quoted: So then which is it?  Does that Amperage matter?  Does using a 500mA charger on a phone that can handle a 1A charger mean that it wont work, or that it will charge more slowly, or will it make any difference at all? And using a 1A charger on a 500mA phone will fry it???

If you hook your 500ma device to a 1A charger you will be fine.

If you hook your 1A device to a 500ma charger it's hard to tell what might happen.  
(a) The charger will definetly be overloaded and may overheat and burn out depending on how it's designed.
(b) If the overloaded charger throttles back the voltage and/or current then your 1A device may or may not be damaged depending on how it's designed.

I would not recommend connecting the 1A device to a 500ma charger, but you will be OK hooking your 500ma device to a 1A charger.

Ugh!

Electrical Engineering = Black Fracking Magic

Quoted: If you sue the 1A charger on a 500mA phone, you will most likely fry the phone. If you do the opposite, it most likely will not work. My .223....

Totally incorrect.

You have a 100 or 200 amp service in your home but it does not blow your lightbulb that draws 1 amp.

More power is always a good thing. Voltage however must be correct. (Or close)

Undercurrent will more likely blow the power supply.

Undercurrent=bad

Overcurrent=good

Your power supply could be 1000 amps and as long as the voltage is correct you will be fine.

Quoted: Ugh! Electrical Engineering = Black Fracking Magic

nah, simple Ohms law

Quoted: Quoted: Ugh! Electrical Engineering = Black Fracking Magic nah, simple Ohms law

Yeah. You can just derive the rest, right?

Quoted: Quoted: If you sue the 1A charger on a 500mA phone, you will most likely fry the phone. If you do the opposite, it most likely will not work. My .223.... Totally incorrect. You have a 100 or 200 amp service in your home but it does not blow your lightbulb that draws 1 amp. More power is always a good thing. Voltage however must be correct. (Or close) Undercurrent will more likely blow the power supply. Undercurrent=bad Overcurrent=good Your power supply could be 1000 amps and as long as the voltage is correct you will be fine.

Thanks for the correction. I'll most likely brain dump it before hitting the "submit" button.

Lord knows, I barely remember having TAKEN EE, let alone anything from the class.

What you say makes perfect sense, of course. Silly of me not to have thought that.

Quoted: Quoted: Quoted: If you sue the 1A charger on a 500mA phone, you will most likely fry the phone. If you do the opposite, it most likely will not work. My .223.... Not quite correct. You could use a 5v/200A adaptor and it would work just fine.  All the aperage rating means on the adaptor is how much current it can handle.  The device will still only take what it needs. Great, this is just what I needed.  More confusion! So then which is it?  Does that Amperage matter?  Does using a 500mA charger on a phone that can handle a 1A charger mean that it wont work, or that it will charge more slowly, or will it make any difference at all? And using a 1A charger on a 500mA phone will fry it???

NO SIR!

It depends entirely on the charge circuit.  Do this with a time based charge circuit (which is common for low cost charge circuits - probably not your cell phone, but unless you know for sure I wouldn't try it) and you will cause  a battery to explode.