NKON LiFePO4 Cell Terminal Snapped Off

...Ghost...

I started my Seplos Mason battery assembly today.

So, I set my torque wrench to about 2Nm to snug up the nuts on the battery cells near the end of the build. I wasn't even letting the torque wrench click, as I just wanted the nuts to be tight against the terminal face. I was 3 away from the final one before I planned to tighten them up to 5Nm, or a bit less, not wanting to damage any cells. The terminal just pulled away from the cell before it got tight. It had to have been a bad weld.

How are NKON on dealing with this sort of thing? Should I drill, tap and fit a replacement terminal? I'd rather not have to do that tbh, as I don't have a drill press.

graememk

Yeah id put it down to a faulty weld, contact Nkon.

munsterfan2

When I had a faulty cell after 6 months they had me ship bad cell back and then sent me a replacement.

...Ghost...

I don't suppose anyone here happens to have the same type of cell spare? Looking at NKON site, they have none available til end of June. Looks like I will have to wait.

Gutted now. I was hoping to check that I had connected everything as it was supposed to be. The build instructions are absolutely terrible on the kit.

...Ghost...

https://www.boards.ie/discussion/comment/122209158#Comment_122209158

What was the process? AnPost don't take batteries and at around 5kg each, they can't be cheap to ship.

munsterfan2

Used GLS to ship back, 37e and NKON refunded that to me also. https://www.gls-one.ie/en Dropped it to the local shop

Big Lar

Possible to configure the SEPLOS as 15s until replacement arrives?

...Ghost...

I'm not sure if can be used with 15 cells tbh. I think I would just wait for the full 16 before commissioning the pack.

I'm looking at fogstar and they have the same cells in stock. It might be worth ordering a single cell from them and collecting from NI.

Regarding the bad cell from NKON, I could return this to them and ask them to credit me the amount off another 16 cells when I am buying another lot in July. I'm now thinking it might be worth having a spare cell just incase I end up having a repeat of this, or I have a different fault needing replacement.

More bad luck I have had. I ordered a UNI-T clamp meter and it didn't work out the box. I tried taking a reading from the DC solar cable and got the same reading for both the north and south panels, even though the south panels would have been producing much more energy at the time. Then I tried checking the cells and got no reading at all. Checked with my old meter and sure enough all cells were reading 3.14V DC, I have sent the UNI-T back.

graememk

https://www.boards.ie/discussion/comment/122212513#Comment_122212513

Regarding the clamp meter, you did have it in DC mode for the current measuring?

Also the same for the cells, it defaults to AC mode

...Ghost...

https://www.boards.ie/discussion/comment/122212662#Comment_122212662

Fair question, but yes. It is good enough to read out that it's set to DC, but I got no readings, or readings I knew were incorrect.

This is the one I got. DC third one from top.

The temp sensor didn't work either. I think the connection was faulty.

...Ghost...

I've decided I am going to attempt to repair the cell myself. I've ordered a helicoil kit, drill guide and 20mm M6 threaded ss grub bolts. They arrive Tuesday.

If on Monday, NKON tell me they have a cell ready for me, I'll pay in advance for it and ship the damaged one back for credit.

If I mess up the repair on Tuesday/Wednesday, I will order a cell from Fogstar.

I want to get this battery built and ready to go. I'm not leaving it laying on the coffee table for 4-6 weeks waiting on a replacement cell.

munsterfan2

They had spares in stock when I needed the replacement.

...Ghost...

https://www.boards.ie/discussion/comment/122213712#Comment_122213712

If they do, i'll go down that road and sure I don't mind having the extra tools there which I've ordered.

...Ghost...

https://www.boards.ie/discussion/comment/122212662#Comment_122212662

Regarding the torque required. 6Nm seems quite high for these cells. If the ring connections from the BMS and balancer are making a clear impression on the aluminium contact surface, surely that is enough torque? I could go to work and borrow a precision calibrated torque wrench for the day, but as one does, I have developed a sense of when something is sufficiently torqued and 6Nm is just over-kill for these. The faulty one sheared off at low torque, below 2Nm, but the other cells I have re-arranged and just made the nuts very tight to the contact surface and I am happy with that. What is your opinion/experience with these?

...Ghost...

Update:

NKON so far have been great to deal with. I did have trouble paying by card for the order, so sent a bank transfer instead, saving me 2%. They updated me when the payment was received and they informed me that there was a delay with delivery due to backlogs. GLS tracking was garbage, only updating the tracking page the evening before delivery.

So, Johan at NKON replied to my email this morning asking me to check the other cells first. I'm satisfied with the level of torque, so I will call them good. I phoned him and he agreed to send a spare cell which I would pay for in advance, including delivery cost. In the mean time, he will arrange for GLS to collect the damaged cell.

I've emailed him with my official request and expect a payment link today to get the ball rolling. I've asked for a coupon code for the damaged cell which I will use against my next order, which I will be placing as soon as the first battery is up and running. I considered having a spare (insurance) cell at the ready, but I decided against it in the end. I'll be collecting the second order when I drive to Germany end of July.

SD_DRACULA

https://www.boards.ie/discussion/comment/122215118#Comment_122215118

I did the same Nkon said the manufacturer of the cells say 9nm can be used but Nkon advised to use 6nm.

I had my torque wrench ready but going to 6nm was a crazy amount of force so I just tightened with the wrench until it was solid.

When I rebuild the pack into separate batteries I will use a digital torque wrench and go for 3 or 4nm I think.

Eleusis

Personally I would try and fix the cell 1st as the chances of the new cell being matched are slim. When you bought the set originally they would come matched. You always have the back up if fixing it fails. Pretty sure Andy's garage has fixed them on his channel before with success

...Ghost...

https://www.boards.ie/discussion/comment/122220978#Comment_122220978

The courier was supposed to collect the cell today. Never showed. My repair kit arrived from Amazon today, so if the cell isn't collected by noon tomorrow, I'll take a good stab at fixing it. If I mess it up, I'll send it back and hope for the best 🤣.

10-10-20

https://www.boards.ie/discussion/comment/122220993#Comment_122220993

Helicoil what now exactly? I'd only helicoil that if you knew for sure what depth that terminal is, otherwise you could hit a pouch or bus bar, or even just weaken the termination and risk localised overheating. Is helicoil recommended by anybody on these things at all?

graememk

https://www.boards.ie/discussion/comment/122221071#Comment_122221071

Isn't a helicoil meant to repair stripped threads? Eg in a blind hole etc.

I agree I don't think there's anything to "drill" into to tap a hole.

...Ghost...

https://www.boards.ie/discussion/comment/122221111#Comment_122221111

From what I have read, some cells come with blank terminals. The consensus is the terminals are safe to drill between 5 and 7mm. A helicoil insert creates a stable surface to insert a stud which would otherwise strip the soft aluminium. True they are normally used on stripped threads, but I have seen the method used in solar DIY forum on blank terminals for 280Ah prismatic cells.

I suspect it likely I would need to balance a replacement cell, right?

Eleusis

https://www.boards.ie/discussion/comment/122221141#Comment_122221141

Didn't realise you had to send it back. Can't believe nkon wasting money on collecting it. It will prob come balanced enough and if you have any sort of active balancer it will balance the new one just fine.

The capacity will be unmatched. You should be able to get the cell report of the replacement and compare it to the report you got from nkon of the set. Maybe they could even try and match the replacement for you.

graememk

https://www.boards.ie/discussion/comment/122221359#Comment_122221359

I think Nkon have had problems with "false" claims, so they look for it back.

As for matching, I wouldn't be concerned as I would say none of them are "matched " like you infer, they are just the same cell

Eleusis

https://www.boards.ie/discussion/comment/122221490#Comment_122221490

I was told by nkon they come matched. (Eve ones do anyway). They are shipped from manufacturer matched. Iv have seen test reports of grade A 280 eve cell at 317ah and also at 299ah.

...Ghost...

Well, the courier collected the cells this morning….probably just as well. No fires in the house tonight 🤣.

The one on order has also been handed to GLS, so I expect it to arrive early next week. I ought to get building the cabinet soon, so I can get the battery mounted if I manage to get it working.

I just hope I have put all the connections to/from the BMS and balancer in the right place.

unkel

https://www.boards.ie/discussion/comment/122212224#Comment_122212224

Good call but not with the Seplos BMS. You could buy a far superior JK BMS though, you'd have that in about a week

...Ghost...

The cell arrived today, so I wasted little time in getting the pack finished. I torqued the cells to the point they impressed the connections into the bus bars. One of the terminals broke just above the bus bar, but I was able to salvage it by securing the nut onto it, screwing an M6 grub bolt into the nut and then using a second nut to connect the bus bar from cell 8 to 9. Connection is solid now and the pack powered up with good readings. Cell 16 (the newly arrived cell) is at a higher voltage than the rest of the pack, at 3.29V compared to 3.14V. I'm sure the balancer will sort that out.

Here's the end result from under the cover. Cables are pretty tidy over all now. I routed and secured the balance cables under PS-A and PS-B. I circled the terminal I repaired.

10-10-20

You should feed that back, it's not an acceptable failure mode as it implies that the terminals could all snap over time and lessens the resale value of those cell types.

slave1

why a different style bus bar on the top right as we look at that photo?

...Ghost...

https://www.boards.ie/discussion/comment/122243335#Comment_122243335

I plan to let them know. I'll also be sure to have an extra cell just in case for the next build. I'll be placing my order very soon for collection now that I have finished this one.

https://www.boards.ie/discussion/comment/122244145#Comment_122244145

I didn't secure one of the flexible bars when I was tightening one of the nuts and the corner of the bar twisted and started to rip. If you look closely, you can see the flexi bus bars twist between terminals and can be torn unless you hold them in place when tightening the nuts.

I decided to just swap it with the 15-16 bar and made the 15-16 connection with a flat bar that came with the batteries. I considered ordering a single flexi bar, but I was just being fussy. I was too lazy to swap the lot of them out with straight bars :)

...Ghost...

Question.

If I am adding another one or two of these batteries, am I best to make a positive and negative bus bar they can all just connect to, or should I be daisy chaining them?

Eleusis

https://www.boards.ie/discussion/comment/122246414#Comment_122246414

Depends on how many amps you want to charge/discharge. Daisy chaining them limit the total charge/discharge to a single BMS. And combining them to a busbar adds them together.

For example

4 X batteries with 200amp BMS, Daisy chained have a max 200a charge/discharge.

4 X batteries with 200amp BMS joined to centralised busbar have a max 800a charge/discharge.

graememk

Well they all need to be in parallel. (All positives together, negatives together)

If your daisy chain is going from positive to positive, it's more or less in effect a bus bar, it's not passing through the BMS of the other packs

If 2 I'd possibly just join them together.

3 or more id get a bus bar.

...Ghost...

https://www.boards.ie/discussion/comment/122248473#Comment_122248473

Hold it! So, this is what I had in my head, but it seemed too simple and I figured the inverter (Solis Hybrid 5kW) would limit the charge/discharge rate anyhow.

Are you saying that if I connect 2 x batteries with 200amp BMS via bus bars, that would let me charge/discharge at 10.4kW? That would essentially let the batteries run the 9kW electric shower without the grid if needed.

Presumably I would need a beefier cable connecting the +&- bus bars to the inverter?

https://www.boards.ie/discussion/comment/122248643#Comment_122248643

Definitely 2 and most likely a third one later in the year.

I haven't even got the first one hooked up and I'm already getting excited about a possible third battery 😂.

Before I connect the first battery to the inverter, aside from turning off the inverter and battery, what is the process for setting it up? Do I need to download any software, or just connect the battery to a laptop and select pylontech from the BMS setting screen? There is so much to read through on here, it's like trying to untangle spaghetti with a spoon.

I'd love to test the battery before the weekend. Picking up a used Laptop later so I can more easily connect to the battery if and when needed.

graememk

https://www.boards.ie/discussion/comment/122250823#Comment_122250823

The batteries could discharge at say 400 amps. But the limit is still the inverter at 5kW (100amps)

...Ghost...

https://www.boards.ie/discussion/comment/122251178#Comment_122251178

That's what I thought alright. So, really the only feasible way is a bigger inverter, or multiple inverters, which is not allowed without an NC7, but is technically possible without being flagged by restricting export to 5kW or 25A?? or whatever the limit is. Ah, what a pain in the behind all this is.