Replacement of Individual Cell?

[Coydon]

I purchased 8 Ganfeng 270+ cells from 18650.com to make my 24V DIY battery. One of the cells came out of the box with a busted vent and fluid sitting on top of it. 18650 sent a replacement cell at the time. These 8 cells sat for a year before being assembled and put into use.

After 4 months of use, the replacement cell has started to swell up. Is there someplace I can buy a single replacement cell that will match close enough? It looks like 18650 has not gotten any more of these Ganfeng cells since the batch I bought from sold out. Could I drop an EVE 280 replacement into this set?

 

[HRTKD]

That's reasonably close. Did you have the 270 Ah cells in a compression fixture?

 

[Coydon]

Yes, it's a wooden DIY case with threaded rod, snugged up while the cells were at low charge.

The Ganfengs have straight up studs- I'm not familiar with how the EVE terminals work, would this require some sort of custom busbar to be fabricated?

 

[HRTKD]

Yes, it's a wooden DIY case with threaded rod, snugged up while the cells were at low charge.

The Ganfengs have straight up studs- I'm not familiar with how the EVE terminals work, would this require some sort of custom busbar to be fabricated?

Shop around. You can find the different terminal variations all over the place. If you find cells with drilled terminals, just add a grub screw to make a stud.

 

[Coydon]

Should the Overkill BMS be able to keep a cell that has ~10Ah more capacity from becoming a runner?

 

[HRTKD]

Should the Overkill BMS be able to keep a cell that has ~10Ah more capacity from becoming a runner?

Which BMS is that? The JBD BMS that they've carried for a few years or their in-house Pathfinder BMS? The former is a good BMS but doesn't have the ability to balance with a lot of amps like the JK Inverter BMS can with 2 amps. I had the JBD BMS from Overkill and it was a very good BMS but my cells were well balanced from the start.

You may find that you'll have to lower the bulk charge voltage a bit to give the BMS more time to balance the cells.

 

[Coydon]

It is the JBD-SP10S009 (100A 8s 24V).

I didn't top balance, but I did leave the cells connected in paralell for over a month before assembly. I've since read in the Overkill manual that this doesn't do anything, but I've also been talking with a tech at 18650 and he seemed to think it should have brought them into a close enough balance that the replacement cell shouldn't have become a runner (if I'm using that term correctly here). I have to get back in touch with him to see what he thinks of the picture I sent.

One odd thing I just noticed is the swollen cell, unlike the rest of them, still feels ice cold despite the fact that I brought it into a heated area a week ago...

 

[HRTKD]

One odd thing I just noticed is the swollen cell, unlike the rest of them, still feels ice cold despite the fact that I brought it into a heated area a week ago...

Given that observation, I would remove that cell from the building and put it someplace safe in case it decides to go exothermic. Do not put it in the trash.