I kinda knew this was going to happen - I used the nickle strips that came with the Sunkko 788H welder I got on eBay and they are clearly under-rated.
On the recommendation of someone here I had picked up some 12.7mm x .25mm tape, but it was so thick that the Sunkko couldn’t weld it.
So my question for you pro battery pack builders is what nickle tape is your go-to tape for a 60A system using the Sunkko?
Thanks,
DougM
Im using 10x0.15mm nickel strips and reinforce serial connections with copper wires if needed.
I’m pretty sure the ones that come with the welder are just nickel plated. Garbage basically.
.15mm thickness should be enough for 40A. I’m pretty sure Enertion uses that thickness.
Just make sure you get actual nickel strips.
if you read the battery experts on endless sphere: 18650 spot welding -how to- ULTIMATE REPOSITORY | Endless Sphere DIY EV Forum then 7x0.15mm thickness is good for about 7A and becomes hot @ 10A already. with 10mm width, that means its good for about 10A and becomes hot at about 15A already (that table is set up for the typical lengths of nickel strips in 18650 builds, i.e. about 30mm. if you make longer connections, the strip resistance increases linearly with length and so does the overall ohmic heat and therefore your losses).
Im always surprised about all these apparently poorly welded battery serial connections in nearly ALL builds I read about. 
Almost all the ones I see on eBay are nickel plate, and the ones that say, “pure nickel” are sold by the kg.
do you have a link to a specific product you could fwd?
10mm .15 thick pure nickel takes like 2-3 weeks to come in from China
Yeah but Enertion has strips for each cell. Each cell will only reach around 15A current draw at peaks. The 40A fuse stops it from doing anymore. That is why I thought it would be okay. Guess I was wrong. Here’s a pic showing what I mean.
there are more serial connections than just the connecting middle ones!
this is my last battery - the middle serial connections I also went with 1 strip per cell … which is not enough with a 20A cell but since its only 30mm short I felt this connection was halfway ok - most often you ask these 20A only for a few seconds anyway:
now the other serial connections on the outside of the battery after its folded:
guess you could use multiple strips and weld them on top of each other or so - at least 3 to match the middle serial strips.
I really like the way how @L3thaltank did it for his pack:
Not sure I will do my next pack with welding rods again, even though it seems to work well and solid.
I have to say, I don’t have a spot welder and since I solder anyway I wouldn’t know why to use nickel strips, they seem flimsy.
thanks everyone for some great ideas!
I always wondered why you go for the soldered copper instead of just adding multiple layers of nickel on top of each other. Is there are reason?
does anyone have a specific link to a good pure nickel strip? all the ones that I am finding are either not the right dimensions or they are nickel plated.
@Lewishong, here is a linkie to the ones I used. They might be slightly under-rated for a high-powered board, but this gives you a starting point on your search:
thank you!
Its 5mm solder wick
on my latest battery I really just added 3-4 nickel strips on top of each other like @Maxid asked. even less soldering heat, but takes a little longer compared to soldering copper strips.
@deucesdown got me into the folded 30mm strip but can’t find it. Anyone have a source of 30mm at .2mm or even .15? As said above if u look at ampacity ratings as decided by people on es everyone pack seems way low even on just the nickel parallel connections.
Some, maybe all the nickel dealers will do custom widths.
