What contact points to use to measure battery voltage?

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Samsung Galaxy S7

Released by Samsung in March 2016. Model SM-G930.

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Samir @samirgunic

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Posted: Jun 2, 2022

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What contact points to use to measure battery voltage?

I have the battery of a Samsung Galaxy S7 (SM-G930F) in front of me and I want to test the voltage. I have a voltage meter (multimeter) and it would be very simple to do if the battery only had two contact points. These type of batteries are very complicated (for the unknowing and untrained) with several contact points. This particular battery has 8 contact points, 4 on each side of what looks like a plastic bit (or is it a chip?) in the middle of the connector.

Where is plus (+) and where is minus (-) on this thing?

Does anyone have a schematic on this type of battery connector?

I wonder how people determine where to place the test leads? By watching YouTube videos? I have also seen a couple of videos with people fiddling around the connector, on the battery side and on the motherboard side, seemingly unknowing where exactly to place the test leads. They seem to place the test leads all over the thing until they get a reading. It all looks highly unscientific. Not knowing where to place test leads could potentially cause a short circuit, especially if you're doing that on the motherboard side and with external power on, like I have seen some guys do it on YouTube. It's like sensing for the light switch in the dark, with crocodiles in every corner of the room.

Also, I wonder why "SN:" is printed on it without any numbers? This battery is supposedly a genuine Samsung battery that I purchased from a reputable seller, as a replacement for the original battery that came with the phone. (This phone has had its motherboard replaced once before by an independent service because I was unable to fix it myself by replacing the battery. Now it has the same problem again: it's not charging.)

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oldturkey03 @oldturkey03

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Posted: Jun 2, 2022

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@samirgunic not sure if this is what you are looking at. Anything further look into what @flannelist is referring to (ZXW and others:-)

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So if I place the test leads between the Positive and Ground contacts I should get a reading? Is that right?

According to a YouTube video I have seen it should be 2.7 V. My battery is reading 0 V. So I have ordered a new battery today from the same seller.

For reference, here is the video:

https://youtu.be/T8URIuTuoyY

Jun 2, 2022 by Samir

@samirgunic a good battery should never be lower than the 2.7V since that will be below it's threshold and it will not charge up ( yes that can be rectified. Another story:-) Your battery should be more in the 3V region. Make sure that your meter in on VDC and the scale is low enough. Red to positive black to ground. 0 V is unusual, yes it could be just double check.

Jun 2, 2022 by oldturkey03

@samirgunic Yes. Exactly. I probably should have also mentioned that in my answer. Even if you have the leads reversed between Positive and ground, it would result in a negative voltage reading. So could still be easily interpreted in this case (though sometimes that's important, negative voltages do appear in circuits). I would definitely say 0 volts is unusual, but certainly not going to power your phone, or take a charge if that's the case.

Jun 2, 2022 by Alisha C

Thank you both for your help. The reason I asked the question is because I wanted to be sure I was doing this right. However, it is not my first time measuring voltage on this battery. Not just this type of battery but this very same battery. I did that about a year ago. As I mentioned, this phone has been serviced once before for the same indication (not charging, not powering on, no LED). I remember I made some notes about the battery voltage in my e-mail to the service/repair shop before I sent it in. I found that e-mail now and in it I wrote that this battery measured 3.2 V when it was brand new. The original battery that I was going to replace it with measured 0 V.

Jun 2, 2022 by Samir

Replacing the battery did not help back then. I suspected it was a problem with power IC and bad solder joints as there were many reports about this and even some DIY videos on how to repair it. I didn't have experience or equipment so I left it to the pros. They told me it was the ROM chip and it was pointless trying to save data and so they offered to replace the motherboard, or return the phone to me without charge. I might as well replace the board and have a second spare phone, I thought. So when it arrived it was working, with this new battery, the battery that I purchased and sent to them along with the phone.

It's interesting turn of events now. Time has come for this new battery to measure 0 V. I hope the second battery I ordered yesterday will kick start this phone. Otherwise, it's likely it will need another round of motherboard swapping or reworking the solder joints. In that case I will do it myself or just call it a day and keep this phone for spare parts. I actually have a second S7 phone that works correctly.

Jun 2, 2022 by Samir

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So if I place the test leads between the Positive and Ground contacts I should get a reading? Is that right?

According to a YouTube video I have seen it should be 2.7 V. My battery is reading 0 V. So I have ordered a new battery today from the same seller.

For reference, here is the video:

https://youtu.be/T8URIuTuoyY — Samir
@samirgunic a good battery should never be lower than the 2.7V since that will be below it's threshold and it will not charge up ( yes that can be rectified. Another story:-) Your battery should be more in the 3V region. Make sure that your meter in on VDC and the scale is low enough. Red to positive black to ground. 0 V is unusual, yes it could be just double check. — oldturkey03
@samirgunic Yes. Exactly. I probably should have also mentioned that in my answer. Even if you have the leads reversed between Positive and ground, it would result in a negative voltage reading. So could still be easily interpreted in this case (though sometimes that's important, negative voltages do appear in circuits). I would definitely say 0 volts is unusual, but certainly not going to power your phone, or take a charge if that's the case. — Alisha C
Thank you both for your help. The reason I asked the question is because I wanted to be sure I was doing this right. However, it is not my first time measuring voltage on this battery. Not just this type of battery but this very same battery. I did that about a year ago. As I mentioned, this phone has been serviced once before for the same indication (not charging, not powering on, no LED). I remember I made some notes about the battery voltage in my e-mail to the service/repair shop before I sent it in. I found that e-mail now and in it I wrote that this battery measured 3.2 V when it was brand new. The original battery that I was going to replace it with measured 0 V. — Samir
Replacing the battery did not help back then. I suspected it was a problem with power IC and bad solder joints as there were many reports about this and even some DIY videos on how to repair it. I didn't have experience or equipment so I left it to the pros. They told me it was the ROM chip and it was pointless trying to save data and so they offered to replace the motherboard, or return the phone to me without charge. I might as well replace the board and have a second spare phone, I thought. So when it arrived it was working, with this new battery, the battery that I purchased and sent to them along with the phone.

It's interesting turn of events now. Time has come for this new battery to measure 0 V. I hope the second battery I ordered yesterday will kick start this phone. Otherwise, it's likely it will need another round of motherboard swapping or reworking the solder joints. In that case I will do it myself or just call it a day and keep this phone for spare parts. I actually have a second S7 phone that works correctly. — Samir

Alisha C @flannelist Rep: 32.4k 23 35 32 · Answer 1 · 2022-06-02T05:42:08-07:00

So even without verifying I would wager that even though this is 8 pins, not all of them are different lines. More than likely the 2 sets of wider pins on the edges are going to be battery positive voltage and ground. This is usually the case, and even from the flex you can tell just by the traces in the cable and where they go. There are 2 big fat traces that very clearly go to either side of the connector. I marked up the picture you attached for reference. I think I got which one was which correct, I was trying to flip it in my brain since my reference is the board side of the connector, not the battery side. You can also see 2 smaller traces in the flexand which pins they connect to if you look closely. Those are generally battery sensor data (temp, capacity, etc...).

Most smart phone batteries are similar, so most of what I just said is experience, and probably a lot of the videos you see are similar, people working from experience. Which can help you identify patterns, what chips look like what and what they might be for. But if you actually want to know the specifics, many people use various paid repair database softwares. ZXW for example, does have the S7 in its database. You may be able to find this documentation independently if you google around, lots of times schematics or boardviews for popular phones make it out into the wild of the internet.

Samir @samirgunic Rep: 35 2 1 · Answer 2 · 2022-06-12T08:41:56-07:00

Samir @samirgunic

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Posted: Jun 12, 2022

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I have received the new battery that I ordered, and on this one it's clearly marked on the connector cable where the plus (+) and minus (-) are located. This is nice, I like this. It's as if they heard my wishes.