Docan 230ah, new welded stud design?

[willh]

Just received first 4 of 16 230ah cells from Docan shipped China to Canada. The welded terminals are different than I expected. They seem to have improved contact area significantly, short of that I'm not sure what to think as I haven't put them to use yet. Are these common now and I have just missed it?

Side note, the first 4 cells look cosmetically excellent and all voltages are 3.29. Just surprised by this terminal, was expecting the circular type with less contact area.

 

[Horsefly]

Be happy. More contact area = good. I assume the welds are done right, so you should be fine.

 

[willh]

Be happy. More contact area = good. I assume the welds are done right, so you should be fine.

Yes, no complaints here. Just had not seen pictures of these on here.

 

[Bluedog225]

That looks like a solid weld.

 

[Horsefly]

Yes, no complaints here. Just had not seen pictures of these on here.

I'm pretty sure I've seen people post about them here already. I don't think I've seen any complaints.

Makes me jealous, actually.

 

[Bud Martin]

I wonder why they do not weld on all 4 sides.

 

[willh]

I wonder why they do not weld on all 4 sides.

Have to agree with you there, can't imagine it wouldn't be an improvement even if unnecessary.

 

[Bluedog225]

Need some destructive testing to know for sure (chuckle).

 

[Horsefly]

I wonder why they do not weld on all 4 sides.

I hadn't even noticed that. Seems like a silly thing to not do all four.

 

[Bluedog225]

Looking at those welds, two is plenty. If you break those, a mistake has been made.

 

[Groscout]

Nice looking cells. I have the same welded studs on 32 Lishen 150s: They have kinda the same story and have been in service about a year. The cells are installed in two 48v batteries that are currently used in a bus. With proper cleaning, torque and a little noalox or oxguard and they will take care of you.

This is a picture of the product that the battery deal was made on:the above cell is a raw lishen 150 below is an example of a welded stud to be installed and shipped.

 

[740GLE]

Odd my 230ah ordered in April had m6 threaded holes and studs.

These def look more robust. I’m worried about stripping the aluminum threads.

 

[AKvalleyguy]

Odd my 230ah ordered in April had m6 threaded holes and studs.

Same here. Not a fan but so far so good. They are stationary for home solar storage so I'm hoping they just sit and do their job for many years.

Just for good measure I have more on the way but of the square pad welded on stud like Willh posted.

Just received first 4 of 16 230ah cells from Docan shipped China to Canada.

I wanted those initially but had to go with the little round circular type, using the little threaded screws that you speak of. I made sure the second order was of the type you have in possession. That little round post and screw was concerning. Hope your build goes very well!

 

[MondeoMan]

Hi All,

I just bought 32 cells, rated 230Ah with the exact same square terminal as shown in the picture from the start of this thread. I bought them from a local reseller (I'm from an Eastern European country). I have reasons to suspect that the reseller buys them in bulk quantities from Docan.
The Gobel Power QR code decoder says they are all EVE 230Ah cells, manufactured around June 2021, but different days.

I have top-balanced them in parallel at 3.55V for a week, then connected 16 of them in series for a capacity test. Discharged about 230Ah starting from 3.55V until the lowest cell reached 2.50V, at a rate of about 0.25 C, so no problems with the capacity.

However, one thing I noticed, 4 cells out of 32 (that's 2 cells in each 16S battery) do not stay in balance from one day to the next.

CC/CV charging with 0.25 C-rate to 55.80V, 14 cells reach about 3.50V and 2 cells only 3.42V.
The BMS balances them to 0.005 V difference during the CV stage and all seems well until the next day.
But the next day, the same pattern repeats: 14 cells reach about 3.50V and 2 cells only 3.42V.

Could those 4 cells be defective? High self-discharge rate? Has anyone seen anything similar?

I'm trying to understand what are the risks of continuing to use them as they are. The batteries are used for a solar surplus ESS (Energy Storage System), charged during the day and discharged at night.
So far, none of the cells have exceeded 3.50V during charging (except for the initial top-balancing at 3.55V).

 

[AKvalleyguy]

However, one thing I noticed, 4 cells out of 32 (that's 2 cells in each 16S battery) do not stay in balance from one day to the next.

As a first and easy check, are the busbars and connections to those two cells all good and clean?

Maybe, move the two offenders to a different location in the pack, to see if the problem follows?

 

[MondeoMan]

Tested yesterday and today.
The problem follows the cell (moves with the cell). I could not see any issue with the terminals (1-2 mV drop between busbar and physical cell terminal base at 60 Amps).

 

[Alkaline]

I wonder why they do not weld on all 4 sides.

I saw a big battery video and I think its for the laser welding machine it can put the terminals on many cells at the same time.

 

[kuranaga]

Be happy. More contact area = good. I assume the welds are done right, so you should be fine.

If done right... laser welding will fuse only a narrow boundary between the original terminal and the stud... and you do not know how both parts contact beneath the laser welding. In my opinion screw holes are better than anything laser welded, it just sounds more sci-fi...

I just wonder why they can't just build the cells with standing up terminals, standing up "ears" where you can screw on a bus bars from both sides, hold one end and tighten the other end, that would be so much easier. Or at least provide a big threaded hole in the flat terminal, at least M8, not these easy to break M6 things.

 

[Hipster]

if they do the welding good - all 4 sides would be nice - i did have one cell that it broke off when i was tightening the screw down - it was replaced free of charge but didnt have a good feeling after that-

i still rather have the lazer welding done - screw in come loose - and once stripped - that happened to me also - forget it - its useless - i couldnt fix it - locktite didnt help -

 

[740GLE]

If done right... laser welding will fuse only a narrow boundary between the original terminal and the stud... and you do not know how both parts contact beneath the laser welding. In my opinion screw holes are better than anything laser welded, it just sounds more sci-fi...

I just wonder why they can't just build the cells with standing up terminals, standing up "ears" where you can screw on a bus bars from both sides, hold one end and tighten the other end, that would be so much easier. Or at least provide a big threaded hole in the flat terminal, at least M8, not these easy to break M6 things.

Because cell manufacturers don’t care about ESS in a cell by cell sale.

Most of these terminal posts are 2nd and 3rd party in stalled once they were wholesaled due to not passing EV spec.