Battery modding in the phone- Hotwiring larger mAh battery.

Thread Starter

cockroach

Joined Apr 3, 2017
4
Hello allaboutcircuits!

I have a phone(iphone 4s) in which the battery swelled. I cut the circuit of the cell, threw out the battery, and confirmed that the phone works. Now, I have several extra batteries, and wanted to wire one to the phone. I would wire them to the original battery connector, and it should just click into the factory place and work.
This phone is a test/experiment/I-couldn't-care-less-for-it phone, so the battery would be taped to the back.
The phone has 4 pins, and the only 4 pin battery I have is an aftermarket Galaxy S4 battery.
(2100 mAh F5 3.7v)

My question is this, is there any reason that it will not work, if I connect the 4 pins pin to pin?

According to my knowledge, both the iPhone and Samsung battery are 3.7v, and the the mAh is just the capacity. The thermistor and data pins should detect battery charge and discharge, and the motherboard would adjust to the battery. My logic with this mod is that if the double sized batteries that fit and work on your phone from ebay work, why can't I strap a bigger(bigger in mAh + physical size, but same output-3.7v) battery to the back.

I've done this before on a different phone, http://imgur.com/a/ls5Ul and the battery held for a week with WiFi and Bluetooth on!

I've been googling a lot, and could not find a lot of information as to why this would not work. I've found one worrying link saying that the bigger the mAh of the battery, the larger the Ohm resistance. Is this true? Would a bigger mAh battery fry the phone? I thought mAh was just the capacity in amper hours, not the discharge rate(3.7v?!).


Would I be able to use a 3 pin battery thus leaving one pin empty?
If I was to use a 3 pin battery, to which pins would I connect them?

The iPhone battery had four of the following pins: + connection, - connection, NTC, and a gas gague
The galaxy s4 battery has these four: + connection, - connection, NTC, and Thermistor
Are the thermistor and gas gauge the same things? Would it work if I connected them pin to pin?

Any info will help a lot, thanks!


n20SDCM.jpg

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Thread Starter

cockroach

Joined Apr 3, 2017
4


Also, could anyone tell me which terminal is positive and which is negative? that's the battery circuit from an iPhone 4s battery.
 
Last edited by a moderator:

Dodgydave

Joined Jun 22, 2012
9,954
To detect polarity you need a Voltmeter, as for the terminals Ntc is a thermistor, i would wire it positive battery to positive phone terminal etc,,,
 

ian field

Joined Oct 27, 2012
6,539


Also, could anyone tell me which terminal is positive and which is negative? that's the battery circuit from an iPhone 4s battery.
When I tried that, it refused to work - my best guess is parasitic inductance of the leads I used. The battery slides into a slot, so no chance of getting at the contacts to add a decoupling capacitor.
 

Thread Starter

cockroach

Joined Apr 3, 2017
4
To detect polarity you need a Voltmeter, as for the terminals Ntc is a thermistor, i would wire it positive battery to positive phone terminal etc,,,
So you mean connect positive to positive, negative to negative, and NTC to NTC? I wanted to do that, but then I read that the phone does a battery check before starting up and won't start if the battery ID is not original. So I thought of using the original battery circuit and connecting it to another battery cell. The problem is that I don't know which part is positive and which is negative in the circuit, not the cell.
 

Thread Starter

cockroach

Joined Apr 3, 2017
4
When I tried that, it refused to work - my best guess is parasitic inductance of the leads I used. The battery slides into a slot, so no chance of getting at the contacts to add a decoupling capacitor.
Tried what exactly? Connecting another battery, or connecting a circuit to the cell? I didn't plan on sliding it in the original slot as it wouldn't fit.
 
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