Faulty Lithium Ion Water Bottle Style Battery 48v13ah

[Nandos]

Hello,

Long time reader, first time poster

I recently purchased a 48v 13ah lithium Ion water bottle style battery from AliExpress, turns out it’s faulty, I’m in the process of trying to fix it, and was hoping for some help.

I’m new to battery technology and hopefully what I’m saying makes sense, as I’m not 100% sure about the correct terminology

When I first fully charged the battery, I tested it with my multimeter and it only had a reading of 31v. At this point I contacted my supplier and they advised me to open the battery and test the voltage of each series on the BMS, which I did.
My results:

1st: 4.16v
2: 8.33v
3: 12.48
4: 16.65
5: 20.82
6: 24.98
7: 29.15
8: 33.31
9: 37.4
10: 41.5
11: no reading
12: no reading
13: no reading

I was then advised to check whether there were any loose wires ect on the battery that looked out of the ordinary, I noticed that there was a nickel strap loose, I connected the loose nickel strap on with my vintage soldering iron and re tested the BMS.

My new results:
4.15
8.31
12.47
16.63
20.79
24.95
29.11
33.27
37.43
41.5
45.7
49.8
53.9

At this point I thought I was Nikolas Tesla and had fixed the battery, however when I turned the battery back on, it only had a reading of 47.1v fully charged.
At this point I went back to my supplier in China, this was his response:

“There is voltage gap on the 13,12,11,10 series(which no voltage before).
Because when it is bad the battery is still used, and now after repair the last 4 series voltage is different with others.
So need to charge the other 4 series to same voltage as others then it can charge fully.
But i think you cannot do it because you do not have the equipment.”

From my understanding of his response, I can fix the battery by charging the other 4 series to the same voltage. But I need special equipment….. I have contacted the supplier for further clarity around what equipment I would need, that was over a week ago and no response back.

Is there anyone that would be able to help me with this?... Any feedback at all would be greatly appreciated

Thanks

 

[Jon NCal]

You can get an RC charger like an icharger that can charge up various numbers of cells (or individually) to whatever voltage you need. Perhaps look in the classifieds.

Some people have adapted a cell phone charger to charge the individual cell groups.

 

[Nandos]

Thanks Jon NCal, your response is appreciated

Would something like this charger be suitable?

http://www.ebay.com.au/itm/Imax-Digital-RC-Lipo-Lithium-Nimh-Battery-Balance-Charger-B6AC-New-version-2-/400805723704?hash=item5d51e1fe38:g:Y6IAAOSwA4dWGjqt

Would I need to remove the individual cells from the pack for them to be charged? Or could I charge them while they're still together in the pack?

cheers,
Daniel

 

[tomjasz]

Yes. That will work. Out of curiosity what cells were used in the build?

For others...is this inability to rebalance the function of a cheap BMS?

 

[Jon NCal]

No need to remove any cells! The icharger will come with alligator clips and you can charge each individual paralleled cell group separately to 4.2V. For example, 5 cells tied together to one form one parallel group, just clip on to the plus and minus sides of that group.

 

[Nandos]

The cells used are Samsung ICR18650 26F 2600mah

Thanks heaps guys!

 

[dogman dan]

I'm confused, yes, the battery is not completely balanced.

But why is a voltage at the cells of 54v becoming 47v after passing through the bms? In general, when a bms shuts off, an even lower voltage results, like more or less half the pack voltage.

I think there is still a problem with the bms.

Should be about 56.4v, once all cells are at 4.2v.