Volt Kensington not working after storage

[saneagle]

Here we go again, same old story. Somebody bought a bike and didn't use it for a very long time. When they got it out, it wouldn't switch on.

I checked the battery. No voltage on the discharge connectors and 36v on the charge socket that wouldn't increase in voltage from charging. At this point, I already knew the problem, but the only question is how bad is it and what can be done.

I whipped the top of the battery off to check the voltages on the multipin connector to find all at 4.01 except cell no.2, which was at zero volts. That's between the brown and red wires next to the black.

Photos coming in moment when I switch to my laptop to post photos.

 

[saneagle]

The BMS will not allow charging while a any cell is below 2.5 v, so my first goal was see if I could get any charge into that cell. I was able to get a couple of pins in there to charge it, but no charge would go in. I jump started it with a single 18650 in parallel that got it up to 2v, but when I applied the single cell charger, the voltage was going down instead of up, so only option is surgery.

After removing the bottom piece and disconnecting the top piece, I pushed out the cell-pack:



then split the black shrinkwrap to get at the cells:

 

[saneagle]

Lifting off the fibreglass covers reveals the weld-plates, and already I can see something. I marked the cells with voltages for you. If you look at the bottom edge, there's a bit of brown stuff concentrated where the sense wire tab bends over the edge of the cell. It possibly shorted there, which could have been nasty or there's some other problem, like a leaking cell.



A new battery from Volt is (choke) £460. I don't see anything special in it. It's fairly well made and some thought went into the layout and routing, though it has failed. A Chinese equivalent is about £180. I have some replacement cells of the same type taken out of another battery that had a similar problem and life. Should I attempt to replace those 5 cells to save someone £180? That is the question.

 

[Nealh]

Those laser cut buss's are or can be a real bugger to pry off , then one has to cut the cell holder to remove the cells as each side is moulded as one single unit .

 

[Nealh]

One can carefully mark the cell shape exactly on the buss , then mark three straight line cuts and dremmel thru the buss keeping to the 0v side by 1mm or 2mm.

Not for d8veh as he knows what to do .

A visual for others to show where to approx. to make the cuts along the tops of the dead cells. This has to be carried out on both sides.
One would of course mark the cell shape and straight cut line prexactly.

If one marks prexactly one should be able to make a cut line just to the RHS of the cell holder containing the 0v cells.

 

[Nealh]

This thread will be useful to Chris Maluszynski as it was also much what he was thinking of .
Want to learn to restore batteries. Where to start? | Pedelecs - Electric Bike Community

One has to weigh up the cell age factor and config of cells to remove .
Also whether one has similar aged cells and type /brand to replace the duff ones with .

One also needs ideally a nice arduino type spot welder and a good power source, replacement cells , buss material etc ,etc.

The main issue is the mechanical cell holding (one will be cutting away part of the moulded cell holder to remove the cells along with the buss) , depending on how good that buss holds on or is able to be pulled off.

 

[Nealh]

For safety one would cut thick card to the other exposed cell buss's and securely tape that card in place to prevent any accidental shorting and just leave the exposed buss of the five cells to be removed.

Partially treat the pack repair as a new build sans BMS so one has no wiring in the way.

 

[Nealh]

As a tutorial Mr H , I think it would be good to carry out the repair as it may be of interest to others such as Chris M.

It isn't often we get out hands on such a battery where we have carte blanche to do with it as we wish, one assumes this is the case with this one !

 

[Chris Maluszynski]

Even though I have been warned and discouraged from attempting such repairs, and I will probably end up heeding that warning, I very much appreciate the mention and will follow this thread with great interest to learn something! Maybe one day I will attempt it.

 

[saneagle]

then one has to cut the cell holder to remove the cells as each side is moulded as one single unit .

AFAICS these cell holders have no lips. they're just plain tubes, so it should be fairly easy to get the cells out. If they were the lipped type, I probably wouldn't bother. I'm just peeling back the strips now to see how easy they are to remove.

 

[saneagle]

OK to continue the story about the battery, the tubes did have lips so I had to Dremmel off the plastic at one end of the cells before I could slide them out.


I used this charger to get the cells to exactly the same voltage as all the other groups. Luckily. I had exactly the same cells, which I had removed from a faulty but fairly new Oxygen battery, to match the good ones:



I used one of thos amazon spot welders to weld in the new strips. The welders are not very controllable, but you can get enough decent welds to do the job. The Sunto welders are much better. If you look carefully, you can see that I cut slits at the ends of the plain strips, which makes them weld much better





Note that there were no insulating rings on the positive ends of the original cells, which I thought was a bit poor. I put them on mine anyway, as you can see in the photo.

 

[saneagle]

I couldn't make the original heatshrink fit, so I replaced with new:


All back together again being careful to make sure that the wires on the bottom connector were not crossed, crushed or trapped. It's now working perfectly.

 

[UrbanPuma]

Thanks for the lesson Saneagle - very informative