0

I have 2 problems:

First one, I can not find the polarity of a laptop battery with which it charges. I don't know much about laptop batteries, and the only thing that is written on the label about it is a giant plus and minus on opposing sides, however I found that there are multiple combinations of pins that have the same voltage passing through them (some of which dont even include the opposing pins that have the + and -) when the battery is plugged in to the laptop, which is plugged in to the power brick. The uncertainty comes at whether that + and - is the thing I am looking for.

Image of the pins

Second is, I cant seem to find the input voltage of the battery to charge it with. As I said, never worked on batteries before so I am not sure which numbers to follow. I also am afraid of measuring the current through battery connector pins on the motherboard when the charger is plugged in because I dont know what will happen if I reverse the polarity, unlike with volts where I just get a minus in front of the reading, so if anyone can tell me that it'd be great too.

Couldnt find anything about these problems on the internet specific to my battery. It's G91J0 and the laptop is Dell Vostro 15 3515. Some numbers just in case they may help:

  • Power brick barrel jack output: 19.5V 3.34A
  • Motherboard battery (the supposed + and -) pins without the battery in: 13V
  • With battery in: 9.7V

And then there are a bunch of other combinations with different voltages. I dont even know if they publish them but I tried to look for some schematics/diagrams but to no avail. Do I just contact Dell?

PS: Just learning, not trying to do something stupid. Everything is in working order and I am just trying to learn about batteries.

Improve this question
3
  • A) Can you share a photo to clarify what you're talking about? B) If you're not comfortable working with batteries, DO NOT WORK WITH BATTERIES... they can pose a serious fire risk if you get things wrong. If you're looking to learn about batteries, then perhaps try somewhere more appropriate (e.g: electronics.stackexchange.com)
    – Attie
    Commented Jun 6, 2023 at 21:38
  • @Attie I added the picture and a short explanation at the end of the first part. Also, I am pretty comfortable with the thing I am doing, which really is just inspecting. Not opening it or anything right now. And yeah, so many boards that I forgot electronics existed and just remembered this one being about hardware too.
    – cocacolaespuma
    Commented Jun 6, 2023 at 21:49
  • I’m voting to close this question because better suited for electronics.stackexchange.com
    – Joep van Steen
    Commented Jun 9, 2023 at 12:52

2 Answers 2

Reset to default
0

As in my comment on your question: If you're not comfortable working with batteries, DO NOT WORK WITH BATTERIES... they can pose a serious fire risk if you get things wrong

From your photo, I'd make an educated guess that:

  • The 2x wider pins at each end are the battery's positive and negative respectively - 4x total, probably connected to the copper area on the PCB with many vias).
  • The 4x smaller pins in the middle (connected to the visible wires) are likely either temperature sense, cell taps, communication with an onboard BMC, or a combination. You will likely be fine to leave these disconnected for both charge and discharge, though repeated cycles of the battery may lead to unbalanced cells and other damage.

NOTE: This is only a guess, and could be wrong... please perform your own sanity checks too.

The battery chemistry and nominal voltage should be printed on the label, which will allow you to calculate the expected number of cells in series. Together this will give you an idea of the charge scheme (current, voltage, time)

photo from OP, with positive and negative labels added

Improve this answer
8
  • Seems to check out, thanks for the guess. Would you know why there are 2 for each polarity?
    – cocacolaespuma
    Commented Jun 6, 2023 at 22:44
  • A pickoff for another voltage requirement as I noted
    – anon
    Commented Jun 6, 2023 at 22:46
  • "Would you know why there are 2 for each polarity" - to handle more current... each pin will have a rating, using two pins doubles that figure.
    – Attie
    Commented Jun 6, 2023 at 22:53
  • @John "A pickoff for another voltage" - unlikely...
    – Attie
    Commented Jun 6, 2023 at 22:56
  • Could also be a feedback circuit. 2 wires that size are not needed for current carrying capacity.
    – anon
    Commented Jun 6, 2023 at 23:02
0

I think the big question is: Why do you need this information?

The Dell battery (not some other) will be properly charged by the Dell charger (not some other).

The battery will (99% of the time) only go in one way so you cannot get polarity wrong.

The charger is labelled for voltage, current and power and your main battery voltage is roughly the same voltage as the charger at full charge.

The battery voltage will vary (go down) as the amount of charge decreases.

Depending on laptop design there may be voltage pickoff points for specific uses.

If you need more precise battery full charge voltage, you should contact Dell Support.

Perhaps get ordinary batteries (such as Alkaline) and learn on these. I have done this to ensure I know what I am doing around batteries.

Improve this answer
2
  • I dont need it for a particular reason, just thought it would be a good learning source as I dont use this laptop anymore. Regarding the polarity question, I want to clarify that I meant the pins of the battery itself, and not the way it connects to the motherboard. Can you also tell me what are "ordinary batteries"? Alkalines, maybe? Thanks.
    – cocacolaespuma
    Commented Jun 6, 2023 at 20:06
  • Yes - Alkaline batteries are good for this work. I added this qualifier to my post.
    – anon
    Commented Jun 6, 2023 at 21:25

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .