Batteries have relatively low internal resistance. So if you apply a high voltage to them, the current flowing into the battery is high, which can charge the battery too quickly and cause it to overheat. Because of this, proper battery charging systems limit the amount of current they'll provide when charging a battery.

When it comes to electronics projects, people often try to build their own simple charging systems, which can potentially be dangerous if they're not aware of all the rules and limitations.

Most professionally made charging systems have all the necessary safeguards and limits built in so that the user doesn't have to worry about anything.

As far as charging iPhones, it's a bit of a grey area. Apple refuses to say precisely what chargers work with what products and there's a lot of mythology on the internet around these issues. The iPhone definitely has some internal circuitry to stop the charging at the right state of charge, but it's not entirely clear to me whether or not the phone has internal current limiting for charging purposes or if it relies on the charger for that. This is way beyond my area of expertise so I won't speculate.

To sum up, I'm not really sure if it matters which charger you use for your phone, because the phone may have all the regulatory circuitry built in. I definitely do know that *something* has to regulate the amount current used to charge a battery, because the battery's own resistance wouldn't be enough to keep current down at safe levels.

In case it's not clear already, charging batteries is a very, very different scenario than lighting a lamp, or powering most other electronics devices.

thanks for all the explanation it becomes become clearer and clearer now

 

thanks for all the explanation it becomes become clearer and clearer now

No problem! I'm happy to help. I'm sure I got a few details wrong in there, but the general ideas are right.

 

No problem! I'm happy to help. I'm sure I got a few details wrong in there, but the general ideas are right.

Ok thanks are you doing anything with RF high frequency project i need some help on that to multiply the frequency triple ..to achieve around 2600 Mhz

 

Ok thanks are you doing anything with RF high frequency project i need some help on that to multiply the frequency triple ..to achieve around 2600 Mhz

Not me! I'm still learning fundamental stuff about DC and low frequency AC stuff - I'm nowhere near ready to tackle RF design challenges.

However, if you do want help with those issues, I'd recommend you start a new thread specifically on that issue. That will help keep this thread focused on its original topic and you're more likely to get the responses you need.