Yes many of the commercial packs i have seen are also have "split end " strips ....like this one from the previous thread..spinningmagnets wrote:This is intriguing. I have seen some nickel strips that had a thin slot right over the end of the cell.......
Intresting indeed !Hillhater wrote:Yes many of the commercial packs i have seen are also have "split end " strips ....like this one from the previous thread..spinningmagnets wrote:This is intriguing. I have seen some nickel strips that had a thin slot right over the end of the cell.......
That is interesting. I guess it forces the current to go down through the cell-foil interface. I like that idea. Thinking about creating a thin slit with a razor blade.spinningmagnets wrote:... some nickel strips that had a thin slot right over the end of the cell.....
Matador, the technology is similar to a TIG welder. However, in TIG welding, you usually have the current go through the part. In this case, it is going from the electrode to the outer copper part. So a bit tricky.Matador wrote:...Pretty sure somebody could reverse engeneer that thing...
Errr ?..No, this time i think you mean 0.05mm thickMatador wrote:That orion welder can weld 0.0020 inch (0.508 mm thickness copper strips) !
That would be awesome !mkp007 wrote: With the split, the Ni plating and tungsten electrodes, there might be a cheap and easy solution.
Yes ! I meant 0.020 inch (0.508 mm) not 0.0020 inch.Hillhater wrote:Errr ?..No, this time i think you mean 0.05mm thickMatador wrote:That orion welder can weld 0.0020 inch (0.508 mm thickness copper strips) !
...unless you meant to say 0.020 inch ?
In a well designed battery pack, every path is analyzed for voltage drop. The goal being to minimize it when possible to and for each cell to see the same resistance.spinningmagnets wrote:I just want to double check my understanding of proper current-flow in a pack. In a high-current pack, the nickel strips that connect the paralleled sub-packs can still be 0.020" thick, but it is the series connections between the paralleled sub-packs that must carry the full peak currents? Meaning: only the series connections need to be much thicker? (also, I assume there should be several thick strips making the series connection?)
I'm pretty sure you meant 0.2mm thick (7.9mils).spinningmagnets wrote:Let us imagine (for the sake of argument) that we have theoretical battery pack that is rectangular in overall shape, using 6P straight inline cell-groups that have been spot-welded using 0.20 inch thick pure nickel strips.
Sounds ok to me. I like that you pick up the current between the two P cells. This way, all the P cells see an equal and low voltage drop. A circuit diagram of a battery pack is a bunch of 3.6V loads connected by resistors. A battery pack designer should create one to be confident in their design. That's what this thread is for https://endless-sphere.com/forums/viewt ... 14&t=84412.spinningmagnets wrote:If we want high current from this pack, the series connections are thick copper bars, three between each paralleled 6P sub-pack. Located in-between every two cells, for intuitive current-sharing between each six-cell P-group.
Yes, I think this is fine based on eTrike's comment below.spinningmagnets wrote:What if we sand the connecting part down to bare metal, and then immediately solder the copper-bar connections onto the nickel parallel plates?
eTrike, I'm not sure I like the idea of an electrically conductive grease in my pack. Is this the stuff you use? How do you apply it so it doesn't get all over the place?eTrike wrote:I live in a fairly wet climate and my main pack uses copper for series and parallel. The packs are half sealed but show no signs of greening in 4+ years in this config. A bigger concern is packs that use steel since that can grow in nasty ways. It is much worse on the coast. Aluminum can grow surprisingly in salt air. Of course solder protects against corrosion as you say. I like no-ox.
kdog, I think most if not all of the copper we see being welded to cells is the multi-purpose 110. I searched for the weldable 122 variety in foil and it is non-existent (at least with my 10min of google searching). At this point, I still think the most practical solution is Ni plated Copper 110 foil because Copper 110 is available in many thicknesses.kdog wrote:....Well according to the copper development assoc there are 871 recognised alloys of copper. You name it- it's there.any conductivity from 4-110%IACS, all tempers, weldability etc... So now I'm a Google expert in copper alloys.
If you take the selection of copper alloys with iacs of between 50-80% and screen for weldability you get about 15 or so that are right on the money. Good to excellent weldability and 2-3 times conductivity of nickel. ( FYI- pure copper rates as not recommended to spot weld ie below poor)...
https://endless-sphere.com/forums/viewt ... 5#p1104439ridethelightning wrote:....the key to making it a smooth job i think is a tungsten tipped electrode. this will not melt like a copper one or stick to the tab. it will also create the resistence needed to create the heat for the weld, at the tip, similar to the effect kdog saw when only using light presseure with his copper electrodes....though...kdog knows all of this, hell, i banged on about it multiple times in a fever of excitement from seeing the copper tab actually welded properly with his MOT welder...
I analyzed a stripe from a pack from Sony laptop ca. 5-7 yrs old on a SEM/EDX microscope and:mkp007 wrote:At this point, I still think the most practical solution is Ni plated Copper 110 foil because Copper 110 is available in many thicknesses.
If using the parallel resistance spot welders, you need to make a slit in the foil to force current downwards to the foil-cell interface. The Ni plating may create higher resistance at the weld interface to help generate more heat.
Interesting. Tin, nickel and silver coatings on copper are quite common. Nickel seems to be better for various reasons. For one, "Tin tends rather easily to form hard, brittle intermetallic phases, which are often undesirable" (ref https://en.wikipedia.org/wiki/Tin).Skrzypas wrote:I analyzed a stripe from a pack from Sony laptop ca. 5-7 yrs old on a SEM/EDX microscope and:
1. They used tin-plated copper.
2. This material easily spot welds on my low power DIY-style MOT spot welder.
3. the stripes have poor fatigue strength (brake easily; one Sony pack I disassembled had perfect condition cells but the spot welds broke)
I asked in a medium company doing metal-plating and they do nickel as well as tin. Whatever I want. Question what would be cheaper in a large scale.
According to a sales rep, the Sunkko 709A that is 220V has a little more power than the 110V version even though the specs are identical. This has also been confirmed in other posts: https://endless-sphere.com/forums/viewt ... o#p1188754kdog wrote:Mp007- I've successfully welded up a 20s6p pack with .1mm copper, with a MOT welder ( it's now upgraded to a bigger transformer) so it's def possible. I don't have direct exp but I highly doubt that a cheapy suunko will do copper. Copper wil eat that 500a for breakfast, You'll need over 1200 pref >1800 I'd say. I think mine is putting out 1500ish but that's a guesstimate. 1.9kw is pretty dismal- check the threads on them I think they're good for .15 nickel max. Don't quote me on this though
ref: https://endless-sphere.com/forums/viewt ... 5#p1165391ridethelightning wrote:...the dynamics in the process of welding copper is quite different from that of metals with higher resistance like nickel.
because it conducts the weld current so well, and also conducts any heat away so fast, it requires much more current to get it to heat to the point where it melts and fuses to the cell. this makes it very difficult to weld, as it requires a huge amount of current in a very short pulse, and any factors such as bad contact or dirty surface could blow the arse of a cell to bits! my solution to this was is to use tungsten rod as the electrode tip,($3 from any good welding store (from tig electode) drilling a hole in the end of the copper dn10 electrode tips(as pictured earlier) and inserting some~15mm long piece of tungsten with a press fit into each electrode tip.
this has a very high melting point, quite high resistance and is very hard. the result is that the tungsten remains hard but glows cherry red for an instant as the weld pulse travels through it, producing the heat that creates the weld. because the copper is so good at conducting the heat away, the area where the weld is is barely warm to the touch afterwards. ( although the welding pens get warm after a while) im absolutely confident that it doesnt get hot enough to damage the cells, while creating a very high current connection....
You have a good point. So one electrode is off the strip touching the battery cell end and the other is on top of the strip. This forces the current to go through the strip/cell interface. This would produce one spot vs. two. But you could keep the one probe stationary and move the other one to different spots on the strip quickly.SlowCo wrote:...When welding a battery pack by hand isn't it therefore better and wouldn't it make it possible to weld copper strip by putting one electrode directly on the cell top/bottom and the using the other electrode to press the nickel/copper strip onto the cell when spot welding? Both on the same cell side of course, not letting welding current flow through the cell. Or is that still damaging to the cell?