Dented 18650 in Luna Cycle battery pack

[Phife]

Hey guys,

I got a 52v 20Ah pack from Luna Cycle, I was involved in an accident and the pack took a hit. I damaged the BMS in the pack and it needed replacement. I replaced the BMS and while I was inspecting the rest of the pack I noticed this damage on one cell on the corner of the pack. The wrapper looks bad and the metal cell case has a small dent.

Its a brand new battery and was very expensive, but im worried about it now. Do you guys have any experience with anything like this? The pack reads 56.8v on the main battery leads and each balance lead reads 4.05-4.06v

Its been about 5 weeks with the battery sitting damaged while I waited for a new BMS, I have not charged it or used it. What do you guys think? Any advice would be appriciated. Im hoping the pack is still ok and useable, or maybe replace the one cell? Can that be done on a pack like this? looks spot welded. Worst case scenario?

 

[Icewrench]

It would be best to replace the dented cell.
It is good that the bent cell is not draining the other cells in the parallel group
but long term may act up.
Find someone with a spot welder near you and it should be an easy repair.
Good luck

 

[Hwy89]

I agree, that cell should be replaced. Since it is on the corner of the pack it won't be that difficult to pull and replace. You should contact Luna and ask them to sell you a single cell. It is a fairly new pack so the replacement will be close to the same capacity as the rest.
If you have not been able to find anyone to make the repair by the first of July send me a PM. I will be in the Seattle area for a couple of weeks and will have my spot welder with me.
EDIT: realized I typed June instead of July.

 

[ScooterMan101]

What brand of cell is that ?

What is the Milli Amp hours of each cell ?

Most business have some replacement parts that they order , interesting to hear if Luna stocks some single cells for each type of pack they sell, for just your type of situation.

Just noticed you have a 2014 Stumpjumper FSR , what is the biggest chainring do you think you could use, that the chainstay would allow ? ( for those of us that use rear hub motors ).

 

[Lurkin]

Burn a house down to save $10? Replace the cell.

 

[dogman dan]

Indeed, that thing stays outside till it's fixed.

 

[Phife]

Thanks for the advice guys, I'll keep the pack outside in a metal box until I can get a replacement cell. Better safe than sorry.

The Cells are the Panasonic NCR18650B cells, they are 3400mAh. I sent an email off to LunaCycle to see if they can sell me some singles, if not, i'll just order some online.

As for replacing the damaged cell, What do you guys think the best way to remove the damage cell is? I have no idea how to repair a pack so any info would be helpful.

How do I remove the spot welded metal strip from the battery? Will I have to replace the metal strip with a new one? Will any kind of spot welder work or does it have to be a specific one? Is there a write up or tutorial on doing this?

Thanks for the offer Hwy89, If I havent got it fixed by then, I may take you up on that!

 

[Phife]

Just noticed you have a 2014 Stumpjumper FSR , what is the biggest chainring do you think you could use, that the chainstay would allow ? ( for those of us that use rear hub motors ).

Im not sure, I got the bike without a crank or chainrings. I had the stock 44-44 that came with the cyclone motor, It fit without issue, theres quite a bit of room between the chainring and chainstay on this bike, Im using 38-44 now.

 

[Hwy89]

Carefully peel the nickle strip off of the ends of the cell using a rolling motion with needle nose pliers. The spot welds should break as you do this. Once both tabs are free, flatten them out and there should be plenty of material to re-spot weld to a new cell. If the cells were glued together you may have to slit the shrink wrap to get that cell out.
Did you see my edit on the previous post?

 

[Jon NCal]

He does sell individual cells on his vaping site:
https://www.wakeandvape.com/panasonic-ncr-3400-mah-18650

 

[Phife]

Thanks for the info, I'll be ordering a couple new cells tonight.

As for removing the damage cell, should I discharge the battery at all? its still at 4.05v, maybe a slow discharge to lower the power still in the battery?

Installing the new battery, do I need to charge it to the same voltage as the rest?

 

[Jon NCal]

I don't think you need to discharge anything. Just be careful. Be aware of the construction of the cells. The outside shell of the cell, and ring around the positive end is negative and can short to the positive end center or positive connecting strip. Obviously the insulating skin of the cell is very thin and can be penetrated easily. Small sparks will probably not hurt anything.

It would be good to precharge the cell up to matching voltage of its group.

 

[Phife]

Can I solder in the new batteries instead of spot welding them in? I cant find anyone local with the proper spot welder and want to get going asap.

I was thinking of just soldering the nickel strips directly to the battery.

 

[madin88]

Can I solder in the new batteries instead of spot welding them in? I cant find anyone local with the proper spot welder and want to get going asap.

I was thinking of just soldering the nickel strips directly to the battery.

i would do it the same way - even if i own a spot welder because if you pull off the nickel from the dead cell, it probably will tear up and it won't work well spot welding that ripped sheet again to the new cell.
If you keep soldering time short, the cell should not suffer damage.

I'm afraid we will see more cases with defects and dented cells in such custom 14s packs.
the case and holder is designed for 13s and what they do is not using the holder to get space for the additional s-group, but than everything is loose inside.
no wonder that there is high risk of damage in an accident or if the pack falls down.

 

[molybdenum]

Batteries are easily destroyed by heat from soldering, but you can do this withoit damaging the cell:

If you opt for soldering, use a powerful model (at least 80 W) with big chisel tip to minimize solder time. I pre- tin both the battery and nickel. I also use a cloth moist with deionized water to rapidly cool the terminals after soldering (pure water is non- conductive, but be careful, as any salts picked up on the way from sweaty hands etc impart conductivity). Having a friend to put pressure between the battery and nickel while you solder will make life easier and allow quenching with damp cloth within a second of applying heat.

Speed is of the essence, and the job should only take 1-2 seconds per cell. Practice with spare nickel and dead cells before soldering in the new battery. I soldered 170 18650 cells for 17s10p this way and it's still working after 2 years.

 

[Phife]

Thanks for the info guys! I really appriciate it. Im going to solder them in, Im pretty confident I can do it and I have a decent soldering station (Hakko FX-888D) I will give it a go!