You mean those microwaves at the convenience stores that always cause my chili cheese hot dog to blow up all over the inside of the microwave, no matter how conservative I am on the time setting?
Xuba cells with Laser welded bus bars
- Thread starter pmtco2
- Start date
You mean those microwaves at the convenience stores that always cause my chili cheese hot dog to blow up all over the inside of the microwave, no matter how conservative I am on the time setting?
PMTCO2:
A couple of questions:
1. Did you order the 'pre-fab' pictured here ( red ones from XuBa) or the Blue ones pictured. You offered 2 links to 2 different items. Not sure which ones you've had delivered.
2. How well have these worked out for you? I am considering the RED ones from XuBa because they come installed in a container.
Concerns that others have offered about these laser welded bus bars included what you do if there is a bad cell. My take on this is that if the bad cell is detected on arrival, then you are in a warranty situation. If not...most of us are not going to be returning bad cells anyway as the freight and hassle is too much. In that case you ( and maybe I ) will be removing the plastic box and then we are back to where everyone else is... ordering another cell if it is available.
If the laser weld is iffy then that is definitely a problem and you are pretty much doing the same thing as if you stripped threads with non laser welded bars ie: drilling and tapping.
There is one concern I have, and that is why I am asking you, and that is that the laser weld on the busbar is a great way to cover up bashed around terminals which ( I read on here) is one of the bad signs of abused and recycled cells.
So... if you have time, could you update us as to which pre fab cells you bought and how they have turned out?
I have not received them yet, but I do intend to post back here when I do.
I ordered what was in the 176ah link, and received a message from the Xuba contact asking if I'd like the red case on them. I actually did not see the response before they shipped, but I am assuming they sent me the batteries encased, like the pic. If they didn't, I can't see why they would not offer the same to you, if you asked.
The other was a link to the same setup, but for the 280ah cells. Just an FYI more than anything, I didn't need 540ah for my purposes, but it's probably more bang for the buck.
My Xuba contact's name is Rain Huang, here's the message I received from him after I paid them:
"The battery module you ordered. We have a good-looking and practical outer box that can better protect the battery outside. Do you need it? I have pictures. You can have a look. If you need it, we will make it like this and send it to you.
Looking forward to your reply. Thank you"
Edit: It did occur to me that the red plastic case could also be a way to cover up dented cells. I'll let you know what I find, should be interesting. It may also be a sales differentiator for Xuba, notice they make a big deal on the laser welding process on their new Alibaba ads. Could be all of the above, as well, we'll see!
I went back and looked at the bus bars in the original post. Those aluminum bus bars look awfully thin to me.
I have bar stock that I plan to use to create my bus bars that is 1/4" and 3/8" thick and 1" width. My battery cells are 280Ah. Maybe the thinner bus bars will be OK for a 176Ah battery. A while ago I calculated what the aluminum cross section needed to be to provide the same - or better - amp capacity as the doubled up bus bars that came with my batteries. As I recall, 1/4" was marginal and 3/8" supported more amps.
I have bar stock that I plan to use to create my bus bars that is 1/4" and 3/8" thick and 1" width. My battery cells are 280Ah. Maybe the thinner bus bars will be OK for a 176Ah battery. A while ago I calculated what the aluminum cross section needed to be to provide the same - or better - amp capacity as the doubled up bus bars that came with my batteries. As I recall, 1/4" was marginal and 3/8" supported more amps.
Good point, hopefully for my purposes, I won't be drawing anywhere near the amps needed for that to be an issue. The highest draw items I have will be an instant pot and the occasional microwave (not at the same time), both around 700w. That's what, <60 amps across 2 packs?
I figured absolute worst case I'm drawing 120 amps at once, for very brief periods.
Just for kicks, here's the rest of the pics they sent.
I agree, that does look like 1/4 stock.
Also, some of the terminals in that one pic do look a bit rough, giving some credence to the notion that these could be cells that have had terminal issues, and are being repurposed as "packs".
So I wonder, are those bars flush welded only, or is there something filling the post hole that gets welded "inside" the terminal as well (if that makes any sense)?
Side note, is it just me, or does Xuba seem to be moving towards selling packs more than individual cells? There are far more ads now for fully assembled packs WITH internal BMS, and of course these partially assembled packs for a little less $$. I don't recall seeing all that many when I was shopping for cells back in November.
I agree, that does look like 1/4 stock.
Also, some of the terminals in that one pic do look a bit rough, giving some credence to the notion that these could be cells that have had terminal issues, and are being repurposed as "packs".
So I wonder, are those bars flush welded only, or is there something filling the post hole that gets welded "inside" the terminal as well (if that makes any sense)?
Side note, is it just me, or does Xuba seem to be moving towards selling packs more than individual cells? There are far more ads now for fully assembled packs WITH internal BMS, and of course these partially assembled packs for a little less $$. I don't recall seeing all that many when I was shopping for cells back in November.
Yikes! What kind of current are you expecting?
That 3/8"x1" bar is good for 524a before it heats up by 30 deg C. The 1/4"x1" is good for 409a.
Electrical: Busbar - DC Copper Busbar Ampacities
The following tables have been provided by the Alliance for Telecommunications Industry Solutions (ATIS), T1 Committee, and represent ampacities for busbar sizes and arrangements typically found in the telecommunications industry.
www.copper.org
I agree that the flexibility of reconfiguring the pack or easily replacing the cells would be good, but those AL busbars should be good for 200a.
Yikes! What kind of current are you expecting?
That 3/8"x1" bar is good for 524a before it heats up by 30 deg C. The 1/4"x1" is good for 409a.
Electrical: Busbar - DC Copper Busbar Ampacities
The following tables have been provided by the Alliance for Telecommunications Industry Solutions (ATIS), T1 Committee, and represent ampacities for busbar sizes and arrangements typically found in the telecommunications industry.
I agree that the flexibility of reconfiguring the pack or easily replacing the cells would be good, but those AL busbars should be good for 200a.
Keep in mind I'm talking Aluminum bus bars, not copper. The Aluminum has a much lower ampacity than copper, somewhere around 50%, depending on which flavor of aluminum.
Hedges
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Those welded aluminum busbars are a lot wider than the screw-down ones I've seen pictures of.
The weld has pretty good circumference.
Surface area of busbar is much larger than a wire of same cross section. Also has no (electrical and thermal) insulation.
Looks to me like it can handle quite a bit of current. I think that is how cells like this were meant to be used.
Even the threaded terminals appear to have plate thicker than thread diameter, more meat than the tapped terminals inside cells.
Could be a different alloy that is stronger, or maybe not. Terminals inside cells may be pure aluminum or chemistry reasons, I'm not sure.
What this design doesn't offer is mechanical compliance.
The weld has pretty good circumference.
Surface area of busbar is much larger than a wire of same cross section. Also has no (electrical and thermal) insulation.
Looks to me like it can handle quite a bit of current. I think that is how cells like this were meant to be used.
Even the threaded terminals appear to have plate thicker than thread diameter, more meat than the tapped terminals inside cells.
Could be a different alloy that is stronger, or maybe not. Terminals inside cells may be pure aluminum or chemistry reasons, I'm not sure.
What this design doesn't offer is mechanical compliance.
Yeah, I was curious about how laser welding works, and stumbled across this:
https://www.mdpi.com/2313-0105/6/3/47
Those appear to be "lap welds". I won't pretend that I have read the whole document yet, but it looks like it was just recently published.
I think the key here, since these batteries will be mounted inside a travel trailer, is keeping the cells from jiggling independently of one another. Too much of that nonsense, and either the weld or the cell terminal itself will just break loose. If they are gonna jiggle, they need to jiggle as a whole pack.
If I compress the packs slightly, and then mount them with some type of vibration absorption foam between the packs and the floor of the trailer, it should be enough.
I don't plan on any off-roading with the trailer obviously, but washboard roads are the worst and I have seen the havoc they can wreak on the inside of a travel trailer.
We're probably worried about nothing, but what if the bus bars were welded without the cells being compressed. Say there was a 1/32" gap between each cell. When you compress them, that's as much as 3/32" of stress on the terminal.
Only time will tell and it could turn out to me much ado about nothing.
Only time will tell and it could turn out to me much ado about nothing.
Ah sorry, I thought I had posted this.....newer listing from Xuba, with a vid the welding process. They are taped together, so I wouldn't say compressed, but I don't see a gap in between the cells:
https://szxuba.en.alibaba.com/produ...tml?spm=a2700.shop_pl.41413.13.2aad41b43mhBLf
I would think aluminum bent like that would exacerbate the problem. The 90 degree angles become failure points as well, with its rigidity. You don't want creased aluminum to be trying to bend itself back and forth over and over, right?
Those appear to be copper, or maybe brass? And if that's to scale, they sure are thin.
Hedges
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Cracks induced, and material can fatigue. Certainly aluminum bent a couple of times can break.
Should be bent to a radius which doesn't induce cracks. Sufficiently long (those look good enough), would provide compliance by elastic not plastic deformation and could be very reliable.
Copper cracks that way too. Flex circuits (copper sheet on polyimide) fracture easily if not "annealed" copper. Some are used for dynamic applications (connect to print head) and others are bent once during assembly.
That's just a drawing, so color probably doesn't match material.
Says welding dissimilar metals, but I don't know just how dissimilar. I would expect aluminum to be used throughout.
My welded AL busbars (also from Xuba) are 1-1/8" wide and 2mm thick
