Prismatic cell terminals with crooked threads - is this typical?

[uberpixel]

After patiently waiting for my cells to cross the ocean and arrive at my door, upon unboxing them, I was less than thrilled to discover that my terminals have been tapped quite crooked.

Is this typical? I can't believe that I'm the only person who has received cells with such poorly tapped terminals, but I couldn't find any mention of this happening to anyone else on the forum. These pictures show a couple of the worst examples, but they are all clearly tapped by hand with varying degrees of misalignment. For clarity, I've run 20mm M6 grub screws down the to bottom of the hole for the pictures.



Can I use these batteries as-is? I brought this to the attention of the reseller on Alibaba and was told that their "engineer" said it would be fine. Well, I'm an engineer, and I don't think these will be fine - when clamped, the load on the terminals will introduce significant stress due to the unequal loading from the single point of contact under the fastener head.

I'd appreciate any thoughts on how to proceed. Clamp them up and hope for the best? Demand a refund? Drill and tap with M8? Drill and helicoil to M6 or 1/4-20? I really don't want to spend a weekend trying to save these cells and risk the potential of damaging them. I have a small drill press but do not have access to a proper machine shop.

- uberpixel

 

[Steve_S]

That is a BODGE JOB ! Likely a kid with a hand drill and hand tap & die set did that. It will not be right and will cause issues. Can the holes be drilled out straight & re-tapped to M8 ? Possibly BUT it will have to be done with a Guide Jig with a drill press to ensure the holes go straight, then manually & gently tapping the threads. This is NOT for the Casual DIY'er to fix, someone with real experience drilling out metal and tapping them has to do it.

 

[mikefitz]

similar problem,

Stud Alignment Concerns

Just received my 16 280Ah LiFePo4 cells that were ordered back in November 2020 and I’m just starting the unboxing process. All cells arrived in physically good condition. As I started to install the M6 studs, I observed an issue with the cells. Some of the terminals on the cells were NOT...

diysolarforum.com

Mike

 

[uberpixel]

similar problem,

Stud Alignment Concerns

Just received my 16 280Ah LiFePo4 cells that were ordered back in November 2020 and I’m just starting the unboxing process. All cells arrived in physically good condition. As I started to install the M6 studs, I observed an issue with the cells. Some of the terminals on the cells were NOT...

diysolarforum.com

Mike

Sorry - somehow I missed this thread, but it looks like the same person tapped our terminals... Are your cells Lishen 272’s? I bought from a different reseller, but they sure look similar to mine.

Anyone know if these are typically tapped by the reseller prior to shipment? Just wondering where this went wrong. It’s really a shame since the cells otherwise look to be in good shape although I haven’t done a capacity test yet to confirm.

-uberpixel

 

[uberpixel]

That is a BODGE JOB ! Likely a kid with a hand drill and hand tap & die set did that. It will not be right and will cause issues. Can the holes be drilled out straight & re-tapped to M8 ? Possibly BUT it will have to be done with a Guide Jig with a drill press to ensure the holes go straight, then manually & gently tapping the threads. This is NOT for the Casual DIY'er to fix, someone with real experience drilling out metal and tapping them has to do it.

Do you think I am justified to ask for some sort of remedy from the reseller? These were purchased from what I believed was a reputable reseller (possibly one of the most frequently mentioned on this forum) but they are so far not offering any solution to resolve the issue.

I can't imagine that these will be okay over their lifetime if nothing is done to straighten the holes.

I'm thinking best case they send me replacement cells or refund my purchase price - worst case they refund enough of the purchase price to pay a machine shop to fix the messed up terminals - although I'm not sure how much a shop would charge to do the work - might be as much as the cells are worth. Fortunately I only ordered 4 cells so far, so 8 terminals to fix - could be worse...

-uberpixel

 

[Steve_S]

Well, I am not sure a "Machine Shop" would do such a thing, I know for certain my machinist would not do it for anyone but his shop only does High Performance Racing Engines and so not quite the place for it. Now if I went to Bob personally to do it, we would likely do it after hours but likely cost a couple of 40's of Canadian Club. You would have to check around but many would be risk-averse as one screw-up could be quite hazardous and potentially costly.

You did not mention the vendor, Alibaba is a site like Amazon or Ebay, the vendors are all separate companies.
Do you have any friends who are Hot Rodders with machining equipment ? Or others who do light machining work for a job or hobby ?
I can do this BUT I have been a Hot Rodder for decades and done auto-restorations (ISCA Quality) and am setup to do such a thing, starting from fresh is easy, fixing holes out of alignment with tight tolerances would still be quite tricky to setup and to make sure it works out and even then I'd give it a 50/50 chance of screw up. You only have about 6mm depth that you can go without breaking through the terminal head.

 

[Bob B]

I saw that other thread ... but yours look a even worse.

Did you buy them from the same place .... as in post #4 on that other thread?

 

[uberpixel]

I saw that other thread ... but yours look a even worse.

Did you buy them from the same place .... as in post #4 on that other thread?

Different source - although those other cells look really similar to mine...

-uberpixel

 

[Solarfun4jim]

I'm getting the distinct impression, that as popularity rises with these cells(across several vendors), 'lesser quality' is being slipped into the mix. I might be wrong...just a feeling i'm getting, the more threads i read lately???

 

[Dzl]

I'm getting the distinct impression, that as popularity rises with these cells(across several vendors), 'lesser quality' is being slipped into the mix. I might be wrong...just a feeling i'm getting, the more threads i read lately???

I was just about to say the same thing, its anecdotal, but it sure seems this way, and that matches with what I observed with the EVE cells too. towards the end of their popularity / availability the quality and consistency seemed to go down considerably.

There are two possibilities that I see (1) as a particular discount cell becomes popular the resellers or the wholesalers they buy from scrape lower and lower in the barrel to meet demand (2) Cell quality actually has not gone down, but it appears that way to us because as a cell rises in popularity you get more and more people sharing their experience, and maybe the people taking the time to share share skew towards those with problems, not those with mediocre experiences. Or maybe (3) a bit of both.

Whatever the case may be, it does seem like many more people are receiving subpar Lishen cells recently, and were receiving subpar EVE cells in late summer to early fall. Anecdotally, with the EVE cells it seemed to mostly be low capacity, the Lishen cells seem to mostly meet or exceed capacity but have more mechanical/cosmetic imperfections (dents, issues with the vent caps, terminals, etc).

 

[XO4001]

After you get your refund I would put a grub screw in a nut and put the nut in a vice, take a piece of pipe or tubing that fit snug over the rest of the grub screw and give it a little bend eyeball the same angle as the wrong tapped hole.
then with some loctite insert and turn to put in a straight position.

 

[jwelter99]

This is crap work by the vendor but not the end of the world to solve. You have a couple options:

1) Using drill press drill a new hole and use a helicoil. You will need to go up in size on the helicoil but this should be done anyhow. 6mm is too small for these cells. 8mm or 10mm is much more reasonable.

2) If it's just crooked but the threads ok (eg: it can take some torque) you can put the bus bar on over the crooked stud, get a m6 spacer you cut to match the intersection angle of the bus bar, put that on top over the stud, then a nut torqued to ~25 in/lb and try hard to forget about it.

 

[schroederjd]

I had the same issue with 3 of the 16 cells Lishen cells I purchased through Basen. I had originally thought of using copper crush washers, then remembered that my busbars are copper... In the end, I found that using serrated flange nuts and grub screws installed with red locktite, I was able to get the flange nuts to dig in to the busbars to the point that I was getting 360 deg of pressure. From there, I'm following the 'try hard to forget about it' approach suggested above.

 

[HRTKD]

After you get your refund I would put a grub screw in a nut and put the nut in a vice, take a piece of pipe or tubing that fit snug over the rest of the grub screw and give it a little bend eyeball the same angle as the wrong tapped hole.
then with some loctite insert and turn to put in a straight position.

I have to wonder how securely fastened into the terminal those OEM posts are. If they're in there tight, I would be very reluctant to try and pull them out.

I'm in agreement with the nut and washer on top of a bus bar solution. As long as the bus bar sits flat on the termina, call it a day.

 

[uberpixel]

Thanks for the suggestions guys!

I'm really annoyed that these terminals are turning into a new weekend project all on their own. Feeling a little less discouraged but not any less annoyed. I'm still hoping the vendor can offer me some kind of solution to address these quality issues.

This pack will be sitting on the tongue of my camper trailer, so I want to make sure the busbars stay intact during vibration/etc. I'm thinking the helicoil (or timesert) would be the most robust option you've shared, but also carries some risk of causing further damage because I'd be removing more of the material in the terminal (strip the bigger hole and I'm done), and the helicoil is probably the most time consuming.

I'll probably rig something temporary so I can capacity test and make sure I don't have additional problems with these cells and then decide how to address this for the long term.

-uberpixel

 

[ArthurEld]

You will be better off with threaded inserts since your cells are going to have a rough ride.
Especially if you plan to use solid busbars.

 

[Steve_S]

I think IF you can get the busbars flush on the cell surface pad and tightened down they'd be OK but I would most certainly use serrated lock washers in any mobile application. When attaching the BMS Harness wires you'd have to be certain the ring connector is flush to the busbar as well or tap the busbar and screw the lead to that is an option too.

I did a quick check and seems like a few vendors had similar issues with Lishen Cells, seems 4 vendors got some of these. While I cannot say for certain, seems like that "batch" came from a Cell Broker who tapped the cells and did a poor job of it (FYI, Virtually all cells leave the factory with "blank" terminals), end supplier has to either tap the holes or weld on studs or busbars.

For future reference to ANYONE Buying Cells.
If offered options to either have holes tapped for bolts/screw, o having welded on studs, go with Welded Studs.
If the Vendor offers welded on busbars - DON'T ! If the cells are NOT Perfectly Matched & Batched you must avoid this as the likelihood of getting a runner in the pack is high and then you're stuck with a cell you cannot swap out if it's not good.

The Most Important thing is to make sure the busbars sit perfectly flush with the contact surface on the cell and that the wire from the BMS Harness is also flush and secure against the busbar. If that can be achieved then they should be ok.

Re-tapping the holes is possible with great care and a drill press, a bit guide is important to ensure that the new hole being drilled in is straight & true with a depth stop of 6mm. The aluminium is soft enough that this is not hard to do if done slowly & patiently. Manually threading the hole with a Tap & Die set again with great patience & calmness can get you there. IF you have no experience in doing this, I'd suggest getting some scrap aluminium pieces and do a couple of practice runs first to make sure you have the "feel" for it, every metal cuts differently and you get a feel for it. Aluminium is very easy to work but also super easy to screw up because it is so soft. Slow & steady wins the race.

PING to @Amy Wan (Luyuan) as an alert to this problem with Lishen Cells which I believe she may have gotten and also shipped to a couple of fo clients not realizing this Serious Flaw existed. Amy, if you got stuck with some of these cells which got shipped to clients consider this as an "alert" that some of these may be flawed and not useable. I'd ping the Basen & Other reps but most have no presence here.

Finally, I would like to reiterate that this serves as an example of potential issues with cells that have holes tapped as this is not the first time such has occurred). With Laser Welded Studs this is a non-issue and in fact you get a better (more secure) connection point, so if possible, buy cells with welded studs.

Hope this helps, Good Luck
Steve

 

[TdKo]

This is what Emely Peng from Shenzen Basen told me yesterday. It is obvious that the brokers and resellers do not sell A-grade goods, but buy factory rejects, rework and then offer them as brand new. A shame.

 

[Steve_S]

This is what Emely Peng from Shenzen Basen told me yesterday. It is obvious that the brokers and resellers do not sell A-grade goods, but buy factory rejects, rework and then offer them as brand new. A shame.

This again highlights the use of Battery brokers as that sort of thing does not leave a factory to goto clients and factories would never store cells or any of their materials in damp/humid conditions that would allow for ANY form of corrosion which takes time to happen, certainly more than the 6 months of allowable shelf life for the stock.

 

[Tuscumbia]

Emily from Basen has sent me the same photos today because I have a bad terminal too. They are hand drilled, thats why some ar not with the same depth and not absolutely vertical. Sometimes they also overdrilled the threat - as with mine. They also sell verry old cells from 2019 (old stock). Everybody can check that on the 15th digit of the qr-code ist the year (9 = 2019, 0 = 2020). 16th digit is the month (1 = jan, 2 = feb, ... A = oct, B = nov, C = dec). If a cell is older than 6 month id need to be cycled one time and is not grade A anymore because cells significantly age if they are older even if they are not in use. The qr code is undependent from the manufacturer with Lifepo prismatic cells. So everybody can check it easy.