2A / 1A / 500mA - Car adapter and Telephone ?

[jean019]

2A / 1A / 500mA - Car adapter, Telephone, and USB hub ?

Hi,
Maybe that's a newbie question but ....
1) My default telephone charger is a 1A. I bought a car charger designed to charge at 2A (for iPad).
Is it dangerous for my phone ?
(I found different answer on forums, so I now asks only to professional electronic man

2) I have different devices to charge on my car. So I bought an 4*USB hub, to plug on the 2A car charger, to charge up to 4* USB devices.
Is it dangerous and why ? (I saw lithium battery exploded on some video so ...)

Thanks !

 

[BradtheRad]

One amp is a lot to push through little phone batteries.

Is that really the amount going through them all the time? Or just for ten minutes as an initial charge rate?

If they get 1A all the time then they'll overheat alarmingly. It will reduce their useful life.

I've had this happen to my batteries.

 

[jean019]

The question behind in fact is :
I don't know if this is the "car charger" which decide to push 1A (or 2A) or the phone which consumes power (ex: 300mA when idle, 1A at full charge).
My car adapter :
**broken link removed**

I found different answer on forums, and if I make a mistake the li-ion battery can explode, in my car, so this is why I ask this question here, to somebody who knows well about electronic.

Note : the idea is to plug the phone (an HTC Desire HD) on the 2.1A plug, I have something else (a bluetooth GPS) to plug on the 1A part.

 

[BradtheRad]

I have no direct experience with li-ion batteries. I understand they require more care to recharge.

Nicads and nimh are tolerant of being overcharged. Nimh don't tolerate overly high current as well as nicads.

Did your phone originally come with li-ion?

The instructions should tell you what kind of charger is safe to use. Naturally they'll say it's only safe to use their own (expensive) brand.

Your phone may have a smart charging circuit that knows when to taper off as batteries fill up (as battery voltage increase). Does it display a message 'charging complete'?

I don't see how a charger would have any way of knowing what size batteries are in the phone. It may give AAA cells the same amount of current as it gives D cells. You'll have to hope it (or your phone) is smart enough to detect battery voltage rising, and react by reducing charging current accordingly.

I don't know what size batteries they're putting in cell phones these days. Gotta be pretty small.

Regardless, you won't know for sure until you insert an ammeter between the phone and the battery pack.

This will not be easy. You'll have to disconnect a wire or connector somewhere. You may have to install a patch wire across connectors. I've resorted to holding pins and needles in my meter clips.

Start by setting the ammeter on the highest range (probably 10A). Careful, because when you use the lower ranges a digital meter may blow a 200mA fuse in response to current greater than 200mA.

(a) See how much current flows initially when the battery pack is low. You need to find out the battery capacity and a maximum safe charge rate. C/10 or C/5 or C/2, etc.

(b) See if charging current declines as the batteries fill up. This can take an hour or more.

(c) See how warm the batteries get. This should not be tried until test A shows safe current flow.