You probably can weld copper at least 0.1/0.15 with copper flux.
I tried with copper flux someone sent me to see if possible.
I was on the edge of successfully welding 0.15mm copper, using 0.1mm nickel plated steel sandwich method, with Infinite slot.
In fact I was successful, on a test cell, whose nickel plating was removed from multiple welds and pull off tests, and then the dremeling off of the copper bits, and scratching the steel casing.
The removal of the test welds increased the resistance, heat, and the chance of achieving a successful subsequent weld, and basically screwed with reality of the welder settings.
When I tried the same combo, welder settings and technique, on a new cell with intact Nickel plating, the welds looked good, felt good, but then ripped off way too easily.
My welder is just a 21$ Purple piece o crap that used a low quality 3S ZEE 5.2AH ā80Cā as the weld battery. I use a separate 12v battery to trigger its mosfets.
I succesfully built 3 small esk8 batteries with it, but using 0.1mm copper and 0.1nickel plated steel.
As the lipo weld battery aged, the pulses needed to increase from about 70, to 95, and the battery needed to be kept warm to very warm, and above 12.2v, and 5 pairs of welds would reduce its voltage from 12.42 to 11.98, and Iād have to recharge it after every 5 welds, and its 12 awg leads were disgustingly hot.
Its last few welds it was emitting the sickly sweet smell of leaking electrolyte, and now it sits completely discharged leads shorted, and awaits recycling.
I have my next Esk8 battery lined up using EVE40PL, but no weld battery.
I find 0.1mm copper so flimsy, I want to use 0.15 or 0.2mm, not just for the resistance reduction, but rigidity of the tabs reaching over the doublefishpapered cell edges. The 0.1mm nickelplated steel helps greatly innthe rigidity departmemt but then becomes a hindrance to soldering the series leads.
My welder can barely do 0.1 mm copper with 0.1 nickel plated steel.
Iām sure 0.1 copper with 0.1pure nickel would be near impossible with it.
.
Unless I remove the nickel plating from the cells steel can.
Infinite slot is too labor intensive. I wanna avoid its requirement.
Maybe the copper flux will allow my desires.
Iām not sure what I am going to do.
My lead acid AGM, as a weld battery, blew up 2 other cheapo welders even with low mS pulses. Too much power. They apparently need a goldilocks battery, though Iāve not risked my purple welder on it, yet.
I dont wanna buy another weld Lipo, whose only use would be as a weld battery, but I might.
I donāt want to buy a better welder just for welding up one 10s1p, and perhaps two 3s1p, but I might.
The 160$ AwithZ UF20B 10kw welder, Nelvick successfully welded 0.2mm copper with unknown thickness of what I think was pure nickel sandwich, using the copper welding flux. But he used a test cell stripped of its nickel plating, and its steel can scratched up from dremelling off subsequent test welds
I donāt want to have to remove the nickel plating from the cellās steel can, just to achieve proper welds.
Wish I had the funds to throw at the problem.
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Just had this random thought thinking about someone who wants a battery built, and it made me chuckle:
3 levels of battery builder:
- not aware enough to know they shouldnāt build someone else a battery.
- aware enough to know they shouldnāt build someone else a battery.
- skilled enough to build someone else a battery.
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- Skilled enough to build somebody else a battery but aware enough that given the liability potential, its not worth the risk/anxiety
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Damn Iām still on level 3
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Level 4, baby 
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- Battery Deconstructers Club -
Whether you are salvaging cells, doing a repair, or just plain effed somthing and need to take it apart. What are your tips, tricks, and specific tools that you like to use.
My main method right now is clenching my ass and using flush cutters.
Knipex 78 61 125 are my cutters of choice. They offer a truly flush cut and have very hard steel jaws. They work pretty well for clipping the remaining nickel spot welds down flush.
They definitely have a better cut quality than some of the cheap Amazon specials
Curious what methods and tools other people are using.
Also if there is a better place to post this let me know.
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Cant be discounted.
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I had an old single protected 18650 that was getting too hot during charging, that I wished to retire and recycle.
To discharge it from a protected 2.85v to 0.0x volts, I needed to remove spot welded circuit board, and I wanted to see if I could salvage protection circuit, perhaps reuse it.
I was able to get a razor blade under the spot welded button cap edge, and gave razor a whack with a block of hard wood, and it sheared off surprisingly easily and cleanly. Had to make sure razorās edge bevel was accounted for. I did not expect it to work at all, but the welds were not what Iād call sufficient for an Esk8 battery
I tried this razor blade shear method with an insufficient strength copper nickel spot weld, with partial successā¦It sheared through the copper easily enough, but the nickel plated steel, not so much.
I found the fine grit stone grinding wheels on the dremel allowed the most precise removal of old welds, with least damage to nearby nickel plating of steel cell can.
On the positive contact, i use 18650 fish paper rings on 21700 Cathodes to try and keep any dremelled dust from getting inside cell, along with a vacuum nozzle immediately adjacent while dremelling.
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Thatās a cool use for 18650 rings, Iāve never thought of that. I always worry that a tiny scrap of nickel is going to fall in there and connect positive to negative.
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Something i didnāt include are some of the tools that i use and those knipex flush cutters are some of the best ive ever used.
Also i use a set of bonsi nippers and ball cutter:
My advice in addition is to be absolutely anal about deforming the negative. Do everything you can to prep to make the negative come off clean and not apply any pulling or leverage against the negative side. I go so dar as to thin the weld with a dremel before cutting or removing. If you break a cell and vent the electrolyte : do not breathe that poison. Itās worse than you think for you
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Awesome thank you for the input and for the tools. And yes those flush cutters are on another level.
Yeah I donāt actively use reclaimed cells on something like pev, not worth it in my opinion. maybe good for a drill battery or flashlights or electronic projects.
Iām definitely going to pay more attention to deforming the bottom of the cell. I am guilty of that.
I also just ordered an arbor press. I think I am going to try to see if I can attach a chisel or similar to shear welds off in a controlled manner. I think I saw someone doing that before. Iāll report back if it works well or not.
And yeah the potential for fumes kinda makes me want to put a fume hood above my work station just as a precaution. Also would be super nice for soldering.
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Iām not sure if this goes here or the noob question thread, apologies if itās in the wrong place.
I have a cordless vacuum (Buture). Iām not sure of the model because the company has discontinued it, so thereās limited information on the website. The problem is that I need a charger for it. The only info I could find is printed on the battery pack
7-cell Lithium-ion 2600 mAh, thereās a sticker on the bottom of the unit that says
Voltage 25.9 15 Watts
I have an adjustable power supply, 3-36V, 60 Watts. When I plug in the power supply, the battery will only allow around 27 volts. Can I use this power supply to charge the battery?
i got a 7cell vaccuum,
super slow charging.
says 32v charging.
I measure 32.15v unloaded.
I suspect Diodes reduce max voltage to 29.4ish, or they just completely rely on BMS to disconnect when a cell reaches 4.25v, or both.
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Thanks, Iāll keep an eye on it while charging
What does āthe battery will only allowā mean?
that PSU looks like an adjustable voltage 1.5A psu.
but not a CC/CV bench top supply?
so iād expect if setting it to 7s*4.2v = 29.4v and the battery was low enough you might try to pull so much current from the PSU that it shuts down. (or burn out)
on the other hand if it does do current limiting to 1.5A, then it would drop the voltage, and you would see that even whe you set it to 29.4v it dropped to something lower to keep the current limited at 1.5Aā¦ ??? Iām guessing iāts the former tho. as this case woudl be less common for a psu that didnāt mention CC/CV.
Just dumping some photos here: 18s8p brick to replace the 21s6p that got dented from michaelwaās 50mph crash. Thought i was going to have to do some funky second layer bs but i was able to sneak all the cells into one stager stack brick with group 1 and 18 turned 90 on the end.
Turnings out pretty clean - insulated with tesa tape except the end groups which have fish paper between them and the rest of the groups. Lots of silicone - thermal adhesive on the temp probes #1 in the center and #2 on group 1 between it and group #5. Doing the danger welds tomorrow or Tuesday if im over subscribed. Might be squeaking it in before carve but im trying not to rush anything.
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Yeah, no more 21s for me. I need to be able to free spin it to check for issue. 
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The power supply unplugged will go to 34-ish volts. When I plug the power supply into the battery and turn it to max, the read out will display 27-ish volts. It does not shut down. After a little while that reading will increase from 27 to 28.2ā¦28.5ā¦and so on. I turned it off at that point because I didnāt know what the hell I was doing.
correct, I donāt think itās a CC/CV power supply.