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Cell Phone Charger

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Feb 14, 2023
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I’m having an electronics wiring issue. I am trying to make a battery bank to recharge phones and run other things as needed.

I’m using Ni-MH batteries as the Lithium batteries won’t fit in the space needed. At first I tried a charging circuit that was intended for a 4.5v Lithium battery but it won’t work. It can charge but not charge a phone. I thought it may be that the circuit is designed for 4.5v and may see less then that so cuts off power to protect the circuits.

I did searching for info on cell phone changing and only found a reference of not charging more then 4.2v. I found info for iPhones. But these are Android.

The batteries are fully charged. A meter shows power available on the leads. When I take apart a charging cable and metered out the two lines needed. Just those connected to a charger and the phone charges. So no other power in the other line is needed. When I connect the battery the phone won’t charge. I have chargers as low at 3v up to 5v so the voltage doesn't matter. I can’t find any info on phone charging specs or Circuits.

Any ides on what is going on?
 

Alec_t

Jul 7, 2015
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Welcome to maker.pro.
I’m using Ni-MH batteries
Some phones communicate with their charger to negotiate a charging current, so a plain battery bank may not suit all phones.
 

Harald Kapp

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Nov 17, 2011
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You can't connect an external battery directly to a cell phone's USB port for charging. The cellphone expects 5 V on the USB power lines. You will need a step-up regulator to create 5 V from your external battery. This is how powerbanks operate.

It is a common misunderstanding that the wall wart used to charge a cellphone is a "charger". It is not. The charger is within the cellphone to be able to control the charging process as good as possible taking into account the charge state of the battery, the temperature etc.
The so called "charger" usually is only a power supply.
Communication between cellphone and power supply, as indicated by @kellys_eye is used to set up possible higher power requirements (voltage, current) between cellphone and power supply only. Lacking this communication, there is usually the fallback to classic USB charging with 5 V / 500 mA which will work, but will take longer than charging with higher power.
 
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