Small pack 3S only 4.15v -- What am I doing wrong?

tjobapuerh

New member
Joined
Feb 10, 2021
Messages
14
Hey guys!

I'm sure the answer is ridiculously simple.
But I'm assembling here my first pack as a little experiment, from used laptop batteries, that I have tested and rated for Ah, and assembled accordingly.
At the outset they were all around 4.15v, and I've assembled them in 3s3p.
I've used individual cell fuses, as seen in the photo. However I can only get 4,15v out of them with my voltmeter -- or 8 point something when I put the test pins on the first pluss (where the red cable is) and the red pluss in the opposite corner: But from the opposite negative (under -- as seen where the negative cable is soldered), I get again 4.15.
What have I done wrong?


IMG-3028.jpg
IMG-3032.jpg




Thanks!!
 
Last edited:

Korishan

Moderator
Staff member
Joined
Jan 7, 2017
Messages
6,448
embed files by attaching them. the Attach button is right below. Also, you can drag/drop into the editor box.

As far as your wiring goes, the cells are wired correctly to each other in the pack. But to me, it looks like you soldered the Pos/Neg wire to only 3 cells that are connected in parallel. But I can't tell for sure as the pictures are too straight on and not offset enough to see the sides of the pack as well.
Just verify to make sure you aren't connecting only your Pos/Neg leads to the same cells. The wires should be on opposite sides, as if you were to draw an imaginary line diagonally through the pack to the opposite corner/edge
 

Wolf

Well-known member
Joined
Sep 25, 2018
Messages
1,460
This should be your current flow. Your busbars are not proper.
Wolf
1621210801813.png
 

tjobapuerh

New member
Joined
Feb 10, 2021
Messages
14
(Managed to embed the photos, thanks Korishan!)

It seems like a combination of your answers somehow are correct.

Altho @Korishan: for the record the plus/minus were wired on each opposite corner, like you say.
(Imagine while looking at the photos, I spun the cube 180 degrees towards the camera)

I don't know maybe I was too tired last night, I really thought I had played with the voltmeter in all possible combinations:
But it turns out that by switching the wires to each respective opposite corner 12v came out!

So you are right Wolf about the current flow -- but the busbars are OK. It's a cube after all: when you turn the thing around it's a mirror, and aligns as you suggest it should. But your photo gave me the idea from where the cables should be! ;)

It explains why the voltmeter was giving me a minus symbol on the voltmeter also (even tho I had red to red and black to black).

Pretty elementary eh? Current flow direction hehe -- Thanks guys!!
 

Korishan

Moderator
Staff member
Joined
Jan 7, 2017
Messages
6,448
We all goof up from time to time. That's why we have others to get a second, third, fourth...... view points on ;)

And yeah, being a cube, was hard to tell which direction you had spun it :p
 
Top