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[Q] Galaxy S4 i9500 - External NFC Antenna not working

24th June 2014, 10:36 AM   |  #1  
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So I have the Galaxy S4 i9500. As far as I understand the NFC antenna is built on the NFC enabled batteries, however the NFC chipset/IC is built inside the mobile mainboard. At the same time there are two contact points exposed at the back of the mobile , which supposedly are for the external NFC antenna.

I have a couple of NTAG205 tags which I need to program for various tasks. What I assumed is that if I am using a battery with NFC enabled , then NFC would work, and it is working and detecting the NFC tag when it is almost tapped with the backplate of the mobile.

I wanted to try on a couple of aftermarket batteries for enhanced mAH rating and a possible longer standby time. So first I purchased a MPJ 3500mAH NFC enabled battery as shown below, with this battery the NFC is working correctly.

MPJ

Then I went on and bought the Onite 2600mAH battery with NO NFC as shown below. So expectedly the NFC was not responding to the tag proximity with this battery.

Onite

However I wanted the NFC to work with both the batteries. I assumed that since the battery just contain the antenna for NFC, so maybe I still can use the NFC functionality , with a non-NFC enabled battery coupled with an external NFC antenna. This setup was supposed to suffice the need for a missing internal antenna by placing an external NFC antenna connected to the exposed contact pins at the back. For the reason I got hold of the following :

Wireless Receiver

This doubled as a wireless charging receiver and the external NFC antenna with respective contact points.


Wireless Receiver

So when i put this wireless receiver on with the no NFC battery , the NFC does not work, supposedly I should be as the external NFC antenna (as visible in the photo) is working and the contact point are pressed firmly against the pins with back cover closed. But when i put the same wireless receiver with the NFC enabled battery, the NFC starts working.

So infact an external NFC antenna is not to substitute the place of a NFC enabled battery , it is just to couple with it to maybe extend the range. Is it correct. ? It tells me that an external NFC antenna is meaningless and will not work with a non-NFC battery, which somewhat kills the purpose of having external NFC antenna pins.

Has anybody tried with a similar setup and can shed some light on the subject and share your experiences.

Thanks.
Last edited by HyperEscape; 24th June 2014 at 01:34 PM.
31st October 2014, 12:38 AM   |  #2  
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same problem here
I`m having the same problem.
After changing for an alternative battery, lost NFC function.
I have bought the nillkin wireless charging with nfc, the charging works ok, but no NFC.
Anyone can help us?
30th January 2015, 12:37 PM   |  #3  
Senior Member
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hmm, thread is 4 months old. I don't want it to get lost because one day it may not be possible to buy a replacement battery with NFC. Sorry but, bump.

This guy seems to have it working but he's using a different antenna from ebay:
https://www.youtube.com/watch?v=rNrUrzUYa6k

Roughly related thread:
http://forum.xda-developers.com/show...2648634&page=2

I will buy that external antenna now, ready for when I can't find NFC batteries

Continued:
http://forum.xda-developers.com/show...2#post58527630
Last edited by jago25_98; 30th January 2015 at 12:53 PM.
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